tag:blogger.com,1999:blog-918083329884286312024-02-21T00:24:24.383-08:00Real-World BiomechanicsTopics on Human Motion: How it is Created, Learned and PerformedBiomechanicshttp://www.blogger.com/profile/01298278786879479411noreply@blogger.comBlogger38125tag:blogger.com,1999:blog-91808332988428631.post-20992163183824823012014-03-06T16:04:00.002-08:002014-03-06T16:09:03.233-08:00All of the presentations from the Symposium on Forefoot Running and Forefoot Walking are now available. Click on "Read more" to get them.<br />
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<a name='more'></a><a href="https://drive.google.com/file/d/0ByBAUy-WaD2HMWhiR0p6Q280bk0/edit?usp=sharing">Forefoot Running Kinematics</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HaU5TekxSQWRxcms/edit?usp=sharing">Forefoot Running Kinetics</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HVWhHODFoM29OTkU/edit?usp=sharing">Forefoot Walking - Kinematics and Kinetics</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HWW1QTXVFaW82a0U/edit?usp=sharing">Plantar Fasciitis</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HLWtwcFVJYjEtSkE/edit?usp=sharing">Forefoot Running and Walking - Metabolic Cost and EMG</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HcmtZTi1VbVp5NFk/edit?usp=sharing">Forefoot Training - Is it the Shoes?</a><br />
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<a href="https://drive.google.com/file/d/0ByBAUy-WaD2HeDF1U1MtZHVYV2s/edit?usp=sharing">Forefoot Training - How to become a forefoot runner or a forefoot walker</a><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Biomechanicshttp://www.blogger.com/profile/01298278786879479411noreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-3439850561990050382014-03-03T13:14:00.001-08:002014-03-06T15:51:47.647-08:00The Forefoot Strike: A Walking and Running Symposium presented at San Jose State UniversitySorry for my blogging absence. Last October, I offered to prepare and deliver a symposium on the Science of Forefoot Running and Forefoot Walking at my University, San Jose State. After 5 months of planning and preparation, the symposium took place this past Saturday, March 1, 2014 at San Jose State University. Presentations were made by me and two of my former students (Krystyna Utzig and Nicole Anecito) The symposium was well attended and audience participation during question and answer sessions was amazing.<br />
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Below is a copy of the Symposium Program. I will be posting on the this blog the Powerpoint presentations used in each of the four (4) sessions. In the future, I will also be posting videos of each symposium session.<br />
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For now, here is the Powerpoint presentation on the <a href="https://drive.google.com/file/d/0ByBAUy-WaD2Hc2IwdEp3dWlaekk/edit?usp=sharing">Kinematics of Forefoot Running</a><br />
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<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Biomechanicshttp://www.blogger.com/profile/01298278786879479411noreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-4994220982399427682013-08-04T14:40:00.000-07:002013-08-06T08:57:03.977-07:00My e-Textbook is Now Available for PurchaseHi all,<br />
<br />
The 2nd edition of my e-textbook is now available for purchase. This is the e-textbook I use in my Biomechanics classes. It presents all of my ideas and examples for how I believe Biomechanics explains and can be used to improve movement. Here are links to the <a href="https://docs.google.com/file/d/0B-Z86kLu4Kv5bTZlbVlJT281LWc/edit?usp=sharing">Table of Contents</a> and a sample section from Chapter 2: <a href="https://docs.google.com/file/d/0B-Z86kLu4Kv5ZXQtNFFmMy1WTjA/edit?usp=sharing">Real-World Biomechanics Chapter 2.1.</a> If you would like to purchase my e-textbook, click on the PayPal link under the heading "Purchase Dr. Kao's e-Textbook".<br />
<br />
Once you complete your purchase on PayPal, I will contact you. The e-textbook is security protected, so you will need a one-time activation code for the PC, Mac, iPad, or Android device you want to install the e-textbook on. You won't be able to "copy and paste" or "print" the text. But, I will send you copies of the Biomechanical Models for each movements presented in the e-textbook. You can print these out and refer to them as you read the e-textbook.<br />
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Thank you for following my blog. I think you will find my e-textbook very informative.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-85389534197325233922013-06-12T11:17:00.000-07:002013-06-12T11:20:42.038-07:00The Biomechanical Model for Minimum Movement Time during Running Walking and Road Cycling 07: The Joint Torque Principle<!--[if !mso]>
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<span style="font-size: 16pt;"><span style="font-size: small;">The sixth fundamental Biomechanical principle </span></span>included in this model is the <b><span style="color: yellow;">Joint Torque Principle</span></b>. This principle states that an increase in joint torque (TJ) is caused by an increase in a muscle force (FM) pulling on the bones that are held together at the joint and/or an increase in the moment arm (dMA) (i.e., the linear distance from the joint’s axis of rotation to the line of pull of the muscle force). The line of pull of the muscle force is determined by connecting a line between the attachments (origin and insertion) of the muscle.<br />
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The equation for the Joint Torque Principle is given here.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAfrfojp_9mBbZ36TBsR7PKrhahdREsH2-1CmVSZJhZrxfhfb_xnch5IuM6IVV41zZzjkQQVFr-3A97527mSmFoVjYK1ZYfQ0w_QP79ONWpAnVNAQXkbXQhpkP1u9bPBxyG_PkJbx1WR3e/s1600/Joint+Torque+Principle+Equation.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="63" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAfrfojp_9mBbZ36TBsR7PKrhahdREsH2-1CmVSZJhZrxfhfb_xnch5IuM6IVV41zZzjkQQVFr-3A97527mSmFoVjYK1ZYfQ0w_QP79ONWpAnVNAQXkbXQhpkP1u9bPBxyG_PkJbx1WR3e/s200/Joint+Torque+Principle+Equation.png" width="200" /></a></div>
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A graphical representation the Joint Torque Principle is presented here.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZSDQ4oAv2ctGxtRIaRjxEOhRzRtLe45nHE8zuWfBBeosCiBf_dpcKaw3Ps2ZHa08XPVsSulrwDN3_Y9lOjuM3k1GxMPcPudZHkaAIrPrq_Xa9HS5wJhv4FR9CuXLxPipjadbQnBfoXmv7/s1600/Joint+Torque+Principle.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZSDQ4oAv2ctGxtRIaRjxEOhRzRtLe45nHE8zuWfBBeosCiBf_dpcKaw3Ps2ZHa08XPVsSulrwDN3_Y9lOjuM3k1GxMPcPudZHkaAIrPrq_Xa9HS5wJhv4FR9CuXLxPipjadbQnBfoXmv7/s320/Joint+Torque+Principle.png" width="320" /></a></div>
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Click on "read more" to view my description of the Real-World application of the Joint Torque Principle to real-world running.<br />
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To create a larger muscle force, three factors that influence the size of the muscle force must be considered. <br />
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<li>The first factor is muscle size. A muscle with a larger physiological cross-sectional area will create more muscle force. The method to increase physiological cross-sectional area is resistance training.</li>
<li>The second factor is muscle length. All muscles have a natural resting length. This natural resting length is found when the muscle is relaxed. Muscles that are stretched to approximately 120% of their natural resting lengths generate the most muscle force.</li>
<li>The third factor is the speed of the muscle contraction. Muscles that are concentrically contracted at slower speeds generate greater muscle force than muscles that are concentrically contracted at faster speeds.</li>
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The moment arm is the distance from joint’s axis of rotation to the line of pull of the muscle force. If the moment arm distance is increased, the size of the joint torque will increase. <br />
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<li>To increase the moment arm distance, you would need to move the line of pull of the muscle force further away from the joint’s axis of rotation. The line of pull of a muscle force is determined by drawing a line connecting the muscle’s origin to it’s insertion. Thus, one method for moving line of pull of the muscle force would be to change the locations of the origin and insertion points for the muscle. This is not option because it would be unethical to perform this type of surgery. </li>
<li>The only way we can change the moment arm distance is by changing the angle of the joint. When the long axes of the two bones connected at a joint are aligned long axis to long axis (i.e., in a straight line), the moment arm distance is the smallest. This is because the line of pull of the muscle force passes extremely close to the joint’s axis of rotation. The maximum moment arm distance is achieved when the long axes of the two bones connected at a joint are perpendicular to each other (i.e., there is a 90 degree angle between the two long axes). In this joint orientation, the line of pull of the muscle force is the farthest away from the joint’s axis of rotation. </li>
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<!--EndFragment--><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-1354139748821467722013-06-01T08:33:00.000-07:002013-06-12T09:54:39.658-07:00The Biomechanical Model to Achieve Maximum Jump Height or Maximum Horizontal Distance 02Hi all,<br />
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It's summer break for me. Hurray!! I will be posting regular updates to the blog from now until the end of August. Thanks for your patience. Here we go!<br />
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<span style="font-family: inherit;">The </span><b style="font-family: inherit;"><span style="color: yellow;">Sum of Joint Linear Speeds Principle</span></b><span style="font-family: inherit;"> is t</span><span style="font-family: inherit;">he second fundamental Biomechanical principle included in the Biomechanical Model </span>to Achieve Maximum Jump Height or Maximum Horizontal Distance.<span style="font-family: inherit;"> </span>This principle states that the jumper’s linear speed is the result of an optimal combination of individual joint linear speeds. The identification of this optimal combination of joint linear speeds is a skill that all individuals interested in understanding human movement must develop.<br />
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Click on "read more" to view my description of the Real-World Application of the Sum of Joint Linear Speeds principle to the <span style="font-family: inherit;">Biomechanical Model </span>to Achieve Maximum Jump Height or Maximum Horizontal Distance and<span style="font-family: inherit;"> to see a graphical representation the Sum of Joint Linear Speeds Principle.</span><br />
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For vertical and horizontal jumping, optimizing the combination of joint linear speeds caused by ankle plantar flexion, knee extension, and hip extension will result in the largest sum of joint<br />
linear speeds and will maximize the jumper’s linear speed when leaving the ground.<br />
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Ankle plantar flexion will cause upward linear motion at the ankle joint and at every joint superior to the ankle. Knee extension will cause upward linear motion at the knee joint and at all joints<br />
superior the knee. Thus, a combination of ankle plantar flexion and knee extension will sum to create greater linear motion at the knee and at all joints above the knee. Hip extension will cause upward linear motion at the hip joint and at all joints above the hip. Thus, a combination of ankle plantar flexion, knee extension, and hip extension will sum to create greater linear motion at the<br />
hip and at all joints above the hip. This greater sum of linear motion will be the linear speed of the jumper’s center of mass when it leaves the ground<br />
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<a href="webkit-fake-url://9E87E5DF-C8D5-46ED-BC9F-855A70F83758/image.tiff" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a>A graphical representation of the Sum of Joint Linear Speeds Principle is presented below.<br />
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<a href="http://3.bp.blogspot.com/-eTaeoJacDc4/UbinuXpya7I/AAAAAAAAACI/242XLsLp7nI/s1600/Sum+of+Joint+Linear+Speeds+Principle+Chapter+6.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="143" src="http://3.bp.blogspot.com/-eTaeoJacDc4/UbinuXpya7I/AAAAAAAAACI/242XLsLp7nI/s320/Sum+of+Joint+Linear+Speeds+Principle+Chapter+6.png" width="320" /></a></div>
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<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-44164699573959557002013-05-08T07:17:00.000-07:002013-05-08T07:17:03.969-07:00May 8, 2013<br />
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Hi all! This semester has been a hectic one for me. I have written a book and I am testing it out in my classes. Putting my thoughts into words has been an enlightening process for me. I have refined, revised, added, and eliminated some of my ideas. I will be editing the book this summer and as I do, I will be updating the blog site. By the end of the summer, I will be making the book available for purchase to anyone following my blog.<br />
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So, look for new posts shortly. Thanks for following my blog!<br />
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Jim Kao<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-91808332988428631.post-67064984345496776042013-01-27T09:31:00.000-08:002013-01-27T09:33:41.251-08:00The Biomechanical Model for Minimum Movement Time during Running Walking and Road Cycling 06: The Angular Impulse-Momentum Principle<br />
The fifth fundamental Biomechanical principle included in this model is the <span style="color: yellow;">Angular Impulse-Momentum Principle</span>. This principle states that an increase in angular velocity of a body segment is caused by an increase in the joint torque (i.e., the turning effect caused by a muscle force), and/or an increase in the application time of the joint torque (i.e., the amount of time the joint torque is applied at the joint) and/or a decrease in the body component’s angular inertia (i.e., the resistance of the body component being moved to the angular motion).<br />
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The equation for the Angular Impulse – Momentum Principle is given here<br />
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<a href="http://4.bp.blogspot.com/-9GCPC88Le2M/UQVaNC3dRlI/AAAAAAAACnM/okySoB4Bfco/s1600/Angular+Impulse+Momentum+Equation.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-9GCPC88Le2M/UQVaNC3dRlI/AAAAAAAACnM/okySoB4Bfco/s1600/Angular+Impulse+Momentum+Equation.png" /></a></div>
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Here is a graphical representation of the Angular Impulse – Momentum Principle.<br />
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<a href="http://3.bp.blogspot.com/-JCIhTDYxVA8/UQVdMVXDflI/AAAAAAAACn0/khJ7WoFHn-k/s1600/Angular+Impulse+Momentum+Principle.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="175" src="http://3.bp.blogspot.com/-JCIhTDYxVA8/UQVdMVXDflI/AAAAAAAACn0/khJ7WoFHn-k/s400/Angular+Impulse+Momentum+Principle.png" width="400" /></a></div>
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Click on "read more" to view my description of the application of the Angular Impulse-Momentum Principle to real-world running.<br />
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In Post 05 for the Biomechanical Model for Minimum Movement Time during Running Walking and Road Cycling, I ended the post by stating I would discuss how to increase joint angular velocity in an upcoming post. Well, this is the post.<br />
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There are three factors that determine the magnitude of a joint's angular velocity: the magnitude of the joint torque, the application time of the joint torque; and magnitude of the angular inertia of the body component resisting the joint torque.<br />
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If we increase the magnitude of the joint torque and/or the magnitude of the application time of the joint torque, then joint angular velocity will increase as long as the magnitude of the angular inertia of the body component resisting the joint torque remains constant.<br />
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Alternatively, if we decrease the magnitude of the angular inertia of the body component resisting the joint torque, then joint angular velocity will increase as long as magnitude of the joint torque and the magnitude of the application time of the joint torque remain constant.<br />
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Increasing the magnitude of the joint torque and reducing the magnitude of the angular inertia of the body component resisting the joint torque will be discussed in upcoming posts. Increasing the application time of the joint torque will be discussed here.<br />
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Increasing application time of each joint torque is accomplished by understanding that every joint rotation has two phases: the preparation phase and the execution phase. During the preparation phase, the joint rotates in the opposite direction from the desired rotation. For example, one of the required joint rotations for running is hip extension. During the preparation phase, hip flexion must be performed. Once the preparation phase has been performed; it is immediately followed by the execution phase. During the execution phase, hip extension would be performed. Therefore, to increase the application time of the hip extension torque, you must perform two actions; optimally flex the hip during the preparation phase and maximally extend the hip during the execution phase.<br />
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During running, the preparation phase begins when the foot collides with the ground and ends when the foot is under the center of mass of the body. The execution phase begins when the preparation phase ends and ends when the foot leaves the ground.<br />
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The optimization of hip flexion during the preparation phase depends on the environment in which the activity is being performed and on the muscle properties of the individual who is running. If the activity is performed in a closed environment (i.e., an environment where the relevant stimuli in the environment for making a decision to move are static (i.e., not changing), then the optimal amount of hip flexion would be 120% of the muscle resting lengths. Running on a track with no other runners would be an example of a closed environment.<br />
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If on the other hand, if the activity is performed in an open environment (i.e., an environment where the relevant stimuli in the environment for making a decision to move are dynamic (i.e., changing), then the optimal amount of hip flexion would be determined by a cognitive evaluation of these relevant stimuli. Cross country running would be an example of an open environment.<br />
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Muscle fiber type (slow-twitch fibers versus fast-twitch fibers) will also influence the optimal amount of hip flexion, knee flexion, and ankle dorsiflexion during the preparation phase. Fast-twitch fibers generate maximum muscle force is a shorter amount of time than slow-twitch fibers. Therefore, an individual with a greater amount of fast twitch fibers in the hip extensor muscles would need a smaller optimal amount of hip flexion during the preparation phase.<br />
<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-74169634116716226232013-01-16T21:00:00.001-08:002013-01-27T09:08:57.445-08:00The Biomechanical Model for Minimum Movement Time during Running Walking and Road Cycling 05: The Linear Speed - Angular Velocity Principle<br />
The fourth fundamental Biomechanical principle included in this model is the <span style="color: yellow;">Linear Speed - Angular Velocity Principle</span>. This principle explains how we create joint linear speed. This principle states that an increase in joint linear speed (s) (i.e., the straight line speed) of a point on a rotating body segment is caused by an increase in the body segment’s angular velocity (ω) (i.e., the rotational speed of the body segment) and/or an increase the radius of rotation (<span style="font-family: Calibri, sans-serif; font-size: 12pt; line-height: 115%;">r<sub>rot</sub></span>) (i.e., the linear distance from the axis of rotation to the point of interest on the rotating body segment). For most human movement, the radius of rotation is the distance from one joint to the next joint connected by a body segment (e.g., the radius of rotation for the upper leg segment would be the distance from the knee joint to the hip joint).<br />
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Click on "read more" to view my description of the application of the Linear Speed - Angular Velocity Principle to real-world running.<br />
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<a name='more'></a>Let's examine what happens when the hip experiences an extension angular velocity. When the hip extends both the torso and the upper leg can rotate. How they rotate is determined by any constraints (restrictions) on each body segment's movements. <br />
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Let's assume your feet are on the ground and you are trying to jump straight up into the air. The ground constrains your feet, your ankles and your knees from moving downward. Since your desired outcome is to go straight up, your feet, ankles and knees will be constrained from moving horizontally by muscle contractions. In this situation, when the hip extends, the upper leg will rotate around the knee joint and the torso will rotate around the hip joint. Thus, a hip extension angular velocity will cause the hip joint and all joints above the hip to move upward.<br />
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Now, let's assume your feet are in the air. When you perform a hip extension movement, the knee and ankle joints are free to move vertically and horizontally. In this case, when the hip extends, the upper leg and torso body segments will both rotate around the hip joint. The upper leg segment will rotate downward and backward and the torso segment will rotate upward and backward. The hip will not move. This is why kicking your legs when your feet are off the ground has very little effect on high you jump.<br />
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So, when you run, your foot, ankle, and knee are constrained against moving downward and backward. This means a hip extension angular velocity will cause the upper leg segment to rotate around the knee joint. When this happens, the hip joint will experience an increase in upward and forward linear speed. Any other body parts attached at the hip (e.g, the torso and the head) will experience the same increase in linear speed. <br />
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There are two factors that determine the magnitude of the increase in linear speed: the radius of rotation and the angular velocity. The radius of rotation for the upper leg segment is the length of the femur. The longer the femur, the greater the increase in linear speed. Thus, a runner with longer leg bones has a Biomechanical advantage. This does not mean a person with shorter legs cannot run just as fast. The person with shorter legs needs to improve the second factor, the magnitude of the angular velocity. An increase in angular velocity will cause an increase in linear speed. How we increase the angular velocity at a joint will be discussed in an upcoming post.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-10806758872669651252013-01-15T07:38:00.000-08:002013-01-15T07:51:04.248-08:00I'm back!!<br />
I finished Fall Semester and I began working on my book. I just finished the first draft. My teaching experiences during Fall Semester and the writing of the book led to some updates for my Biomechanical Models. Click on the links below to see the updated Biomechanical Model for Running, Walking & Road Cycling. In my next post, I will continue the explanation of the Biomechanical Principles used to construct this model.<br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Biomechanical%20Model%20for%20Linear%20Motion%20to%20Achieve%20Minimum%20Movement%20Time%20-%20Running,%20Walking%20&%20Cycling.pdf">Biomechanical Model for Running and Walking</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Biomechanical%20Model%20for%20Linear%20Motion%20to%20Achieve%20Minimum%20Movement%20Time%20-%20Running,%20Walking%20&%20Cycling%20(1%20of%203).pdf">Top of the Model</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Biomechanical%20Model%20for%20Linear%20Motion%20to%20Achieve%20Minimum%20Movement%20Time%20-%20Running,%20Walking%20&%20Cycling%20(2%20of%203).pdf">Speed Up Side</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Biomechanical%20Model%20for%20Linear%20Motion%20to%20Achieve%20Minimum%20Movement%20Time%20-%20Running,%20Walking%20&%20Cycling%20(3%20of%203).pdf">Slow Down Side</a><br />
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-13451393202337350042012-12-04T10:20:00.002-08:002012-12-04T10:21:04.134-08:00Posting UpdateI have been extremely busy with end of the semester assignments, labs, grading, and preparing for exams. I plan to post new material immediately after I submit my semester grades. Please keep visiting my blog and the new material should start being posted around December 20th.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-56308032611392399882012-11-09T07:07:00.001-08:002013-01-15T07:49:53.555-08:00The Biomechanical Model for Minimum Movement Time during Running and Walking 04 - The Sum of Joint Linear Speeds Principle<span style="font-family: inherit;">The third fundamental Biomechanical Principle included in Biomechanical Model for Minimum Movement Time during Running and Walking is the <b><span style="color: yellow;">Sum of Joint Linear Speeds Principle</span></b>. This principle states that the linear speed of any point on the human body is the summation of linear speeds at that point caused by individual joint angular velocities. In general terms, any joint angular velocity will cause all points on a rotating body segment connected at the joint, and all points on any body segment attached to that rotating body segment, to move with linear speed. A second or a third joint's angular velocity will do the same. The linear speed of any common body segment will then be sum (addition) of the linear speeds of segment caused by each individual joint's angular velocity.</span><br />
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<span style="font-family: inherit;">Click on "read more" to view my description of the Real-World Application of the Sum of Joint Linear Speeds principle to the Running and Walking Biomechanical Model for Minimum Movement Time.</span></div>
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Specifically, for running and walking, hip extension angular velocity will cause all points on the torso segment, and all points on any body segment attached to the torso segment, to move with linear speed. Knee extension angular velocity will cause all points on the upper leg segment, and all points on any body segment attached to the upper leg segment (i.e., the torso segment), to move with linear speed. Ankle plantar flexion angular velocity will cause all points on the lower leg segment, and all points on any body segment attached to the lower leg segment (i.e., the upper leg segment and the torso segment), to move with linear speed. Since all three joint angular velocities will cause a common body segment (i.e., the torso segment) to move with linear speed, the Summation of Linear Speeds Principle tells us the total linear speed of the torso segment (i.e., the linear speed of the body) is the sum of the torso's linear speed due to hip extension angular velocity added to the torso's linear speed due to knee extension angular velocity added to the torso's linear speed due to ankle plantar flexion angular velocity.</span><br />
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Below is a graphical representation the Sum of Joint Linear Speeds Principle<br />
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<a href="http://4.bp.blogspot.com/-ucKnzDqGAVE/UJ6OUWkfHnI/AAAAAAAACIc/T9GLjwK06QQ/s1600/Sum+of+Linear+Speeds+Principle.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="160" src="http://4.bp.blogspot.com/-ucKnzDqGAVE/UJ6OUWkfHnI/AAAAAAAACIc/T9GLjwK06QQ/s320/Sum+of+Linear+Speeds+Principle.png" width="320" /></a></div>
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-62243879583387079602012-11-07T21:50:00.000-08:002013-01-15T07:49:53.556-08:00The Biomechanical Model for Minimum Movement Time during Running and Walking 03 - The Linear Conservation of Momentum Principle<span style="font-family: inherit;">The </span><b style="font-family: inherit;"><span style="color: yellow;">Linear Conservation of Momentum Principle</span></b><span style="font-family: inherit;"> is t</span><span style="font-family: inherit;">he second fundamental Biomechanical principle included in the Biomechanical Model for Running and Walking </span>to achieve minimum movement time.<span style="font-family: inherit;"> This principle is derived from Newton’s First Law of Motion (Linear). This principle states that to maintain a constant state of motion, any </span><b style="font-family: inherit;"><span style="color: yellow;">factors that would slow the body down</span></b><span style="font-family: inherit;"> must be balanced by </span><b style="font-family: inherit;"><span style="color: yellow;">factors that speed the body up</span></b><span style="font-family: inherit;">. If the factors that slow the body down exceed the factors that speed the body up, the body slows down (i.e., the state of motion changes). If the factors that slow the body down are less than the factors that speed the body up, the body speeds up (i.e., the state of motion changes).</span><br />
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<span style="font-family: inherit;">Click on "read more" to see a graphical representation the Linear Conservation of Momentum Principle.</span><br />
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<a href="http://3.bp.blogspot.com/-a6NffRAwGlM/UJ5-LRdWJPI/AAAAAAAACIM/7rT1tHREHY8/s1600/Linear+Conservation+of+Momentum+Principle+2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"></a><a href="http://3.bp.blogspot.com/-a6NffRAwGlM/UJ5-LRdWJPI/AAAAAAAACIM/7rT1tHREHY8/s1600/Linear+Conservation+of+Momentum+Principle+2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="197" src="http://3.bp.blogspot.com/-a6NffRAwGlM/UJ5-LRdWJPI/AAAAAAAACIM/7rT1tHREHY8/s320/Linear+Conservation+of+Momentum+Principle+2.png" width="320" /></a></div>
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-76510506995904670252012-10-21T18:17:00.000-07:002013-01-15T07:49:53.557-08:00The Biomechanical Model for Minimum Movement Time during Running and Walking 02 - Putting the Biomechanical Model Together<span style="font-family: inherit;">Today, I am beginning the series of posts related to how the Biomechanical Model of Running and Walking to achieve minimum movement time is put together.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The Biomechanical Model of Running and Walking is constructed using the Biomechanical Principles presented in my posts labeled "The Basics" plus a few additional Biomechanical Principles that are specific to this particular model.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The procedure for constructing the model is straight forward. You place the most relevant Biomechanical Principle at the top of the model. The second Biomechanical Principle overlays the first principle wherever similar boxes exist. The remainder of the Biomechanical Principles overlay the preceding principles in a similar manner. The order of principles will be explained as the model is constructed. The completed model was shown in my post titled "The Biomechanics of Running and Walking 01".</span><br />
<span style="font-family: inherit;"><br />
Click on "read more" to learn how the model is constructed. I start with an explanation of the most relevant Biomechanical Principle for this model. </span><br />
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<span style="font-family: inherit;">The most relevant Biomechanical principle included in this model is the<b><span style="color: yellow;"> Linear Speed Principle</span></b>. <span style="text-indent: 36px;">This principle states that a decrease in </span><b style="text-indent: 36px;"><span style="color: yellow;">movement time (<i>t</i>)</span></b><span style="text-indent: 36px;"> (i.e, the time it takes to move from point A to point B) of the body is caused an increase in the body’s linear </span><span style="color: yellow;"><b style="text-indent: 36px;">movement speed (</b></span><span style="letter-spacing: 0px;"><i><span style="color: yellow;">s</span></i></span><b style="text-indent: 36px;"><span style="color: yellow;">)</span> </b><span style="text-indent: 36px;">(i.e., the straight line speed of the body) and/or a decrease in the </span><span style="color: yellow;"><b style="text-indent: 36px;">distance to be traveled (</b><span style="text-indent: 36px;"><b><i>l</i></b></span><b style="text-indent: 36px;">)</b></span><span style="text-indent: 36px;">.</span></span></div>
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<span style="font-family: inherit;">The equation for the Linear Speed Principle is given here.</span><br />
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<a href="http://1.bp.blogspot.com/-qGgC3CZNPM8/UIRVSoQgM-I/AAAAAAAACGs/ZduJLQX18zc/s1600/Linear+Speed+Principle+Equation+(blog)-1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-family: inherit;"><img border="0" src="http://1.bp.blogspot.com/-qGgC3CZNPM8/UIRVSoQgM-I/AAAAAAAACGs/ZduJLQX18zc/s1600/Linear+Speed+Principle+Equation+(blog)-1.png" /></span></a></div>
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<span style="font-family: inherit;">A graphical representation the Linear Speed Principle is presented here.</span></div>
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<a href="http://3.bp.blogspot.com/-eiCyCB0GeQs/UISZvceT5KI/AAAAAAAACHE/10bzPhuzDjw/s1600/Linear+Speed+Principle.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-family: inherit;"><img border="0" height="125" src="http://3.bp.blogspot.com/-eiCyCB0GeQs/UISZvceT5KI/AAAAAAAACHE/10bzPhuzDjw/s200/Linear+Speed+Principle.png" width="200" /></span></a></div>
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<span style="font-family: inherit;">There are two questions to consider when implementing this principle:</span></div>
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<li style="text-align: left;"><span style="font-family: inherit;">How do I increase movement speed?</span></li>
<li style="text-align: left;"><span style="font-family: inherit;">How do I decrease the distance traveled?</span></li>
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<span style="font-family: inherit;">The answer to the first question will be addressed in my next post. The answer to the second question is the following:</span><br />
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<span style="font-family: inherit;">When you "plan" to run a desired distance, you should "actually" run that distance.</span></div>
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<span style="font-family: inherit;">For example, if you are planning to do a 3.0 mile run, then run 3.0 miles. In other words, do not run 3.1 miles or 3.2 miles or any distance greater than 3.0 miles. How is this accomplished? Two answers:</span></div>
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<li><span style="font-family: inherit;">When you are running a curved portion of the run, run as close to the inside of the curve as possible.</span></li>
<li><span style="font-family: inherit;">Between the curved sections of the run, run a straight line to connect the curves.</span></li>
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-56729096476589800612012-10-16T08:06:00.000-07:002012-10-16T08:06:07.580-07:00UpdateIt's been a crazy couple of weeks. I've had mid-term exams in all my classes. Things should get back to normal this week. I'll be posting more information soon.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-20484490384828487612012-10-08T08:08:00.002-07:002012-10-08T08:08:16.110-07:00Posting Comments and QuestionsI just realized I had the settings set incorrectly for allowing anyone to post a comment or question. I think I fixed it. I look forward to hearing from you.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-48978259978708514492012-10-08T06:24:00.001-07:002012-10-08T06:24:48.894-07:00Vertical Jump - Here is what I See (2)So, when does the application time for the hip extension torque, the knee extension torque, and the ankle plantarflexion torque end? This is the easy part, they all end when the foot leaves the ground. At this point, any further plantarflexion, knee extension, or hip extension will merely push the feet downward. There will be no additional upward movement of the joints. Thus, any kicking of the legs or swinging of the arms will have no effect on jump height.<br />
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The next important event is landing. Click on "read more" to read the Biomechanical explanation for how to land with the lowest magnitude (i.e., size) of internal forces that must be absorbed by the bones, cartilage, ligaments, and tendons.<br />
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<b>Landing after a vertical jump for maximum height</b></div>
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After you reach your maximum jump height, your body will fall back to earth. When the body makes contact with the earth, an external ground reaction force (GRF) is applied to stop the feet from continuing to move downward. The magnitude (i.e., size) of the external GRF is determined by three factors: your speed when you hit the ground, your mass, and the amount of time each joint moves downward before actually stopping. If the magnitude of the external GRF is reduced, then Newton's 3rd Law of Motion, the Action-Reaction Principle, tells us that the magnitude of the body's internal forces will also be reduced.<br />
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<u>The Three Factors that Determine the Magnitude of the External GRF</u><br />
<ol>
<li><b>Speed</b>: There is not much you can do about your speed when you hit the ground. It is determined by how high you jump. The higher you jump, the faster you will be travelling when you make contact with the ground and the greater the magnitude of the external ground reaction force.</li>
<li><b>Mass</b>: Your mass can be modified, but not during the jump itself. If you decrease your fat mass over time by dieting and exercise, the magnitude of the external ground reaction force will decrease.</li>
<li><b>Time</b>: The only thing you have control over during the landing after a jump is the amount of time each joint moves downward before actually stopping. If we increase this time by applying eccentric joint torques, then the magnitude of the external ground reaction force will decrease. </li>
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The time the joints in the body continue to move downward during a jump landing is controlled by three torques in the lower extremity: an eccentric ankle plantarflexion torque, an eccentric knee extension torque, and an eccentric hip extension torque. </div>
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Eccentric torques slow down a joint's rotation. On the other hand, concentric torques speed up a joint's rotation. During the acceleration phase, a stronger concentric plantarflexion torque causes a faster plantarflexion rotation. But, during the deceleration phase, a stronger eccentric plantarflexion torques causes a slower dorsiflexion rotation. The same is true for knee extension (concentric contraction during the acceleration phase; eccentric contraction during the deceleration phase) and hip extension (concentric contraction during the acceleration phase; eccentric contraction during the deceleration phase).<br />
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So, here is how the three eccentric torques combine to slow the body down when landing after vertical jump:</div>
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<li>The first consideration is the position of the foot when the body makes contact with the ground. If you land on the forefoot, both the foot and the tibia are free to rotate. An ankle dorsiflexion rotation occurs because the heel and the ankle joint can move downward. The speed of this dorsiflexion rotation is controlled by an eccentric plantarflexion torque. The application time of the eccentric plantarflexion torque begins when the foot makes contact with the ground and ends when the heel makes contact with the ground.</li>
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<li>If you land flatfooted, there is no application time of the eccentric plantar flexion torque. This means that all joints in the body instantaneously stop moving down for a very brief moment; but this is significant event because the magnitude of the external GRF will be very large.</li>
<li>Flexing your knees and hips after the heels make contact has no effect on the magnitude of the external GRF.</li>
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<li>The second torque is an eccentric knee extension torque that controls the speed of the knee flexion rotation. The application time of the eccentric knee extension torque begins when the foot makes contact with the ground and ends when the heel makes contact with the ground or when the knee no longer moves in a downward direction.</li>
<li>The third torque is an eccentric hip extension torque that controls the speed of the hip flexion rotation. The application time of the eccentric hip extension torque begins when the foot makes contact with the ground and ends when the heel makes contact with the ground or when the hip joint no longer moves in a downward direction.</li>
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<b>As long as the ankle, knee, and hip jointscontinue to move downward and the heel does not make contact with the ground, then the amount of time that all joints in the body move downwards will increase. This will result in a smaller external ground reaction force AND a smaller sum of internal joint forces.</b></div>
<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-33514456683238504402012-10-06T15:25:00.001-07:002013-01-15T07:49:53.553-08:00The Biomechanical Model for Minimum Movement Time during Running and Walking 01Today, I am starting a new category of posts on the blog: The Biomechanics of Running and Walking. In the next few days I will also begin a category of posts related to The Biomechanics of Angular Motion. Information related to these two new categories will be put forth simultaneously with the posts related to Jumping.<br />
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I hope that presenting the Biomechanics of three different types of motion will make it easier for everyone who is following my blog to find something interesting and valuable. I invite you to post comments related to these three topic areas. Enjoy. Click on the links below to see the Biomechanical Model for Running and Walking.<br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Biomechanical%20Model%20for%20Running%20and%20Walking.png">Biomechanical Model for Running and Walking</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Top%20of%20the%20Model.png">Top of the Model</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Speed%20Up%20Side.png">Speed Up Side</a><br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20for%20Running%20and%20Walking/Slow%20Down%20Side.png">Slow Down Side</a><br />
<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-26774621074726278312012-10-04T23:10:00.001-07:002012-11-09T13:34:56.919-08:00The Biomechanical Model to Achieve Maximum Jump Height or Maximum Horizontal Distance 01<span style="font-family: 'Times New Roman';">The Biomechanical Model to Achieve Maximum Jump Height or Maximum Horizontal Distance is constructed using the Biomechanical Principles presented in my posts labeled "The Basics" plus a few additional Biomechanical Principles that are specific to this particular model. </span><br />
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The procedure for constructing the model is straight forward. You place the most relevant Biomechanical Principle at the top of the model. The second Biomechanical Principle overlays the first principle wherever similar boxes exist. The remainder of the Biomechanical Principles overlay the preceding principles in a similar manner. The order of principles will be explained as the model is constructed. The completed model was shown in my post titled "The Basics 08".</div>
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<span style="font-family: Times;">Click on "read more" to learn how the model is constructed. I start with an explanation of the most relevant Biomechanical Principle for this model. </span></div>
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The most relevant Biomechanical principle included in this model is the<b><span style="color: yellow;"> Projectile Motion Principle</span></b>. A projectile is an object that has been projected (thrown, struck or kicked) or dropped into the air. In sport and physical activity there are three types of projectiles: (1) round projectiles (e.g., a tennis ball, a golf ball, a baseball, a softball, a basketball, a volleyball, a soccer ball, etc.), (2) non-round projectiles (e.g., a football, a discus, a javelin, a Frisbee, etc.), and (3) the human body (e.g., when it is running, high jumping, pole vaulting, playing volleyball, playing basketball, etc.).</div>
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This principle states there are three factors that determine vertical jump height and horizontal jump distance. The first factor is the jumper’s<b> <span style="color: yellow;">linear speed (s)</span></b> (i.e., how fast is the jumper moving in a straight line when he/she becomes a projectile). The greater the jumper’s linear speed when he/she becomes a projectile, the greater the vertical jump height and/or the horizontal jump distance.</div>
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The second factor is <b><span style="color: yellow;">relative projection height (RPH)</span></b> (i.e., the height of jumper’s center of mass when he/she becomes a projectile minus the height of the jumper’s center of mass when he/she stops being a projectile). RPH does not influence vertical jump height. For horizontal jump distance, three conditions must be considered: (1) when RPH is zero, the jumper is flying over flat ground; (2) when RPH is positive, the jumper is jumping downhill and horizontal jump distance will increase when compared to a RPH of zero; and (3) when RPH is negative, the jumper is jumping uphill and horizontal jump distance will decrease when compared to a RPH of zero.</div>
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The third factor is the jumper’s <b><span style="color: yellow;">projection angle</span></b> (i.e., the angle from horizontal that the jumper follows at the beginning of his/her flight). In order to maximize the vertical jump height, the jumper’s projection angle must be 90 degrees. For horizontal jump distance, three conditions must be considered: (1) when RPH is zero, the jumper’s projection angle must be 45 degrees; (2) when RPH is positive, the jumper is flying downhill and the jumper’s projection angle should be less than 45 degrees (the exact value depends on how large is the positive RPH; the larger the positive RPH, the smaller the projection angle); and (3) when RPH is negative, the jumper is flying uphill and the jumper’s projection angle should be greater than 45 degrees (the exact value depends on how large is the negative RPH; the larger the negative RPH, the greater the projection angle).</div>
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The combined effect of the jumper’s linear speed, the jumper’s projection angle and the RPH determines the jumper’s <b><span style="color: yellow;">time is in the air (t)</span></b>.</div>
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Based on these Biomechanical concepts from the Projectile Motion Principle, the following can be concluded. In order to maximize vertical jump height, you must increase the jumper’s linear speed and the jumper’s projection angle must be 90 degrees. In order to maximize horizontal jump distance, you must increase the jumper’s linear speed, the jumper’s projection angle must be optimized for RPH, and RPH should be positive if possible.</div>
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A graphical representation of the Projectile Motion Principle is presented in below.<br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-EWCtN3tw2LY/UG53-h-0oFI/AAAAAAAAB1U/vbNW7tvdfQ8/s1600/Projectile+Motion+Principle.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="" border="0" height="311" src="http://3.bp.blogspot.com/-EWCtN3tw2LY/UG53-h-0oFI/AAAAAAAAB1U/vbNW7tvdfQ8/s400/Projectile+Motion+Principle.png" title="" width="400" /></a></td></tr>
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<span style="font-size: small;">Projectile Motion Principle</span></td></tr>
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-57654012242361045962012-10-03T14:49:00.002-07:002012-10-03T14:49:51.399-07:00Message from Dr. KaoIt's been a crazy week. I gave mid-term examinations in two classes. I will be posting new material tomorrow, October 4, 2012.<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-51989062569837950282012-09-30T14:44:00.003-07:002012-09-30T14:49:59.879-07:00The Basics 08: Biomechanical ModelingUp to this point, I have posted some unique ideas related to Biomechanics (see The Basics 01, 02, 03, and 07). I am not aware of any other Biomechanist who has written about these ideas. I have also posted some very traditional Biomechanical concepts (see The Basics 04, 05, and 06). However, I do believe my interpretations of these traditional concepts is unique. I will finish this introduction to The Basics with the following statement:<br />
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<b><i>No matter what kind of movement (linear or angular) you are performing, the seven basics I have posted so far WILL be a part of every explanation on how to achieve your desired movement outcome.</i></b></div>
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Of all my ideas, this statement is the most unique aspect of my understanding of Biomechanics. It implies that their is a key set of Biomechanical Principles that are relevant to the creation of all human movements. To demonstrate my rationale for making this statement, I need to introduce an organizational tool I call Biomechanical Modeling. As I go through the analyses of many types of movements, I will utilize this tool to show the cause and effect relationship between Biomechanical Principles and desired movement outcomes. Through these analyses of movement, it will become apparent why I made the statement above.<br />
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<span style="background-color: rgba(255, 255, 255, 0);">Click on "read more" to learn about Biomechanical Modeling. </span><br />
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<a name='more'></a>First, some history on the term Biomechanical Modeling. I learned of this term after reading the textbooks of Dr. James G. Hay. I was fascinated with his concept of linking Biomechanical Principles to "explain" how movements are created. When I started teaching, I tried to incorporate his methodology into my instructional repertoire. But, as I attempted to teach Dr. Hay's method of Biomechanical Modeling, I found I struggled with the logic of his Biomechanical Modeling method. I wish I had had the opportunity to communicate with Dr. Hay, but unfortunately he past away in 2002.<br />
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I then embarked on a journey of investigated reasoning to develop my own interpretation of Biomechanical Modeling. I present this interpretation below. I will always be grateful to Dr. Hay for his influence on my understanding of Biomechanics. I hope to honor his memory by taking his original concept and modifying it in a way that he would find acceptable.</div>
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Biomechanical Modeling is a graphical representation
method to organize the Biomechanical Principles that are used to create human motion
outcomes. Biomechanical models are specific to the desired human motion outcome you are trying to achieve. For example, when you perform a vertical jump, one desired outcome is to achieve the greatest linear height. The Biomechanical Model of Jumping for Height or Distance is applicable to ALL jumping movements that have the same desired outcome. For example the model would be applicable in the following sports: in basketball - jump shooting and rebounding, in volleyball - spiking, blocking and serving, in track and field - the high jump, in football - catching a football and blocking a pass attempt, and in baseball - catching a ball that is over your head. For all of these movements, the Biomechanical Model is the same. But, the interpretation of the model will depend on the context of the movement. Thus, the interpretation of the model for a volleyball spike will be different than the interpretation of the model for high jump in track and field.<br />
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The procedure for constructing a Biomechanical Model is straight forward. You place the desired outcome at the top of the model. You connect the most relevant fundamental Biomechanical Principle to that desired outcome. Relevancy is determined by the type of movement (linear or angular motion) and the desired outcome. You repeat this process of connecting relevant fundamental Biomechanical Principles to each other until all have been placed. When you are done, you will have a diagram that shows all Biomechanical Principles that are relevant to explain how the human body can achieve a desired movement outcome; as well as, the interconnecting relationships between all of these principles.<br />
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Click on this link to download the Biomechanical Model of Jumping for Height or Distance.<br />
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<a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Biomechanical%20Model%20-%20Jumping%20for%20Height%20or%20Distance.pdf">Biomechanical Model of Jumping for Height or Distance</a><br />
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On upcoming posts, I will explain how the model was constructed (i.e, the relevant Biomechanical Principles and how they are connected) and, more importantly, how to interpret and use the model for Real-World Applications.<br />
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<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-82098665557042959612012-09-29T22:35:00.001-07:002012-11-09T06:31:22.065-08:00The Basics 07: The Sum of Joint Linear Speeds PrinciipleIn The Basics 06, you learned that the Angular Velocity - Linear Speed Principle tells us that joint angular velocities will cause all points on a rotating body segment, and all points on any body segment attached to a rotating body segment, to move with linear speed. If two joints are rotating, then the linear speeds of any common points due to each individual joint's angular velocity are summed (added) together. If a third joint rotates, the linear speed <span style="background-color: rgba(255, 255, 255, 0);">of any common point would increase again. This represents The Summation of Joint Linear Speeds Principle.</span><br />
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Click on "read more" to view my description of the Real-World Application of the Sum of Joint Linear Speeds principle to the vertical jumping for maximum height.<br />
<span style="background-color: rgba(255, 255, 255, 0);"></span><br />
<a name='more'></a>There are three joint torques that are responsible for creating upward speed of your whole body when you leave the ground for a vertical jump: hip extension torque, knee extension torque, and ankle plantar flexion torque.<br />
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The hip extension torque will create hip extension rotation. The hip extension rotation will result in angular velocity of the torso body segment and the upper leg segment. The angular velocity of the upper leg segment will create upward linear speed at the hip joint, all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints. The angular velocity of the torso body segment will create upward linear speed at <span style="background-color: rgba(255, 255, 255, 0);">all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints. </span><br />
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<span style="background-color: rgba(255, 255, 255, 0);">The knee extension torque will create knee extension rotation. The knee extension rotation will result in angular velocity of the upper leg</span><span style="background-color: rgba(255, 255, 255, 0);"> segment and the lower leg segment. The angular velocity of the lower leg segment will create upward</span><span style="background-color: rgba(255, 255, 255, 0);"> linear speed at the knee joint, hip joint, all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints. The angular velocity of the upper leg segment will create upper linear speed at the</span> hip joint, <span style="background-color: rgba(255, 255, 255, 0);">all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints.</span><br />
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<span style="background-color: rgba(255, 255, 255, 0);">Finally, t</span><span style="background-color: rgba(255, 255, 255, 0);">he ankle plantarflexion torque will create ankle plantarflexion rotation. The ankle plantarflexion rotation will result in angular velocity of the lower leg</span><span style="background-color: rgba(255, 255, 255, 0);"> segment and the foot segment. The angular velocity of the foot segment will create upward</span><span style="background-color: rgba(255, 255, 255, 0);"> linear speed at the ankle joint, knee joint, hip joint, all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints. The angular velocity of the lower leg segment will create upper linear speed at the knee joint,</span> hip joint, <span style="background-color: rgba(255, 255, 255, 0);">all spinal vertebral joints, both shoulder joints, both elbow joints, and both wrist joints.</span><br />
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When a jump sequence is performed correctly, all of these upward linear speeds are summed (added) together creating whole body upward speed when you leave the ground . Now it's time look at the vertical jump video clip and see if you can see this principle being used.<br />
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<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-7467522964523432232012-09-28T15:55:00.000-07:002012-09-28T15:55:06.018-07:00The Basics 06: The Angular Velocity - Linear Speed PrincipleAfter reading The Basics 04 and 05, you now know that joint torque, application time of joint torque, and angular inertia are the three modifiable factors that can increase joint angular velocity. The Angular Velocity - Linear Speed Principle explains the relationship between joint angular velocity and the linear speeds of points that are part of, or connected to, the rotating body segment.<br />
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Click on "read more" to learn more about The Angular Velocity - Linear Speed Principle.<br />
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<a name='more'></a>The Angular Velocity - Linear Speed Principle states the following:<br />
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If you increase a joint's angular velocity, any point that is part of, or connected to, the rotating body segment will experience an increase in linear speed. In addition, the greater the radius of rotation to any point that is part of the rotating body segment, the greater the linear speed of that point. Finally, points that are connected to, but not part of, the rotating segment will move with the same speed as the attachment point with the body segment.<br />
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Note: radius of rotation is defined as the distance from the joint to the point of interest on the rotating body segment.<br />
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Real-World Example (Vertical Jumping)<br />
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When a jumper extends his knees during the execution (upward) phase, a knee extension torque causes a knee extension angular velocity. This knee extension angular velocity causes all points that are part of the rotating body segment (the upper leg including the hip joint), or connected to the rotating body segment (the torso and the arms), to rotate around the joint. The points on the body segment closer to the knee joint rotate with the smallest linear speeds. The points on the body segment farther away from the knee joint (i.e., the hip joint) will have the greatest linear speeds. The knee extension angular velocity will also cause all joints that are connected to the hip joint to move at the same linear speed as the hip joint. This includes all of the spinal vertebral joints and all of the upper extremity joints (shoulders, elbows, and wrists).<br />
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To put as simply as possible, when the knee joint extends, the hip joint and all joints attached to the hip joint (spinal vertebral joints and all upper extremity joints) will move at the same linear speed.<br />
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<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-55227297515090343912012-09-27T21:51:00.000-07:002012-09-28T05:33:06.043-07:00Muscle MemoryI had another interesting discussion today with my students. The topic was the term "muscle memory". I want to share my thoughts on the topic with all of you. The most important thing you need to know is that muscle fibers have "no memory". If you pull out a muscle fiber and apply an electrical stimulus to it, you will see it contract. When you remove the electrical stimulus, it will relax. You can do this ten times, a hundred times, even a thousand times and every time it will do the same thing. That's all a muscle fiber does. There is nothing to memorize.<br />
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Learning requires a permanent change in the long-term memory of a motor program (i.e, the pattern and intensity of electrical signals to the muscles that create the movement). Motor programs are stored in long-term memory (LTM) and LTM is part of the brain. The problem is this: I hear people use the term "muscle memory" when they are talking about learning a motor program. This unfortunately leads to incorrect ideas about how we learn to perform movements. People believe all you need to do is move the body a few hundred times and the muscles will remember what to do. Nothing could be further from the truth.<br />
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Click on "read more" for an explanation of how movements are actually learned.<br />
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<a name='more'></a>Learning a movement pattern requires the brain to be actively involved during the learning process. When the brain is involved it actively identifies relevant internal and external sensory information. Then, the brain selects the appropriate motor program from long-term memory for the desired movement. Once the motor program is selected, it is modified in short-term memory by taking into account the <span style="background-color: rgba(255, 255, 255, 0);">relevant internal and external sensory information. The brain then uses the motor program to send electrical signals down the spinal column and out the peripheral nervous system to muscles. This is when the muscles contract and movement occurs. </span><br />
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<span style="background-color: rgba(255, 255, 255, 0);">Learning occurs when you "deliberately practice" the entire process with the intent to improve the motor program. Deliberate practice increases the likelihood that a permanent change in the motor program occurs. This change is stored in long-term memory. It is not stored in any muscles.</span><br />
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<span style="background-color: rgba(255, 255, 255, 0);">Good teachers, coaches, instructors, and rehabilitation specialists must develop instructional activities that help the learner perform deliberate practice. We call these these specialized instructional activities "learning experiences".</span><br />
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<span style="background-color: rgba(255, 255, 255, 0);"><br /></span><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-91808332988428631.post-712844134380377992012-09-26T23:11:00.000-07:002012-09-26T23:19:22.347-07:00The Basics 05: The Angular Impulse - Momentum Principle <span style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); font-family: Times, 'Times New Roman', serif; text-align: left;">If you read the Basics 04, you know that joint torques create joint rotations; and, you would be correct to conclude that stronger joint torques create faster joint rotations (i.e., faster angular velocities). But, is joint torque the only factor that creates faster angular velocities? According, to the Angular Impulse - Momentum Principle, joint torques are not the only factor that creates faster angular velocities.</span><br />
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<span style="font-family: Times, Times New Roman, serif;">The Angular Impulse - Momentum principle is derived from Newton's 2nd Law of Motion (angular). This principle states that a change in joint angular velocity is directly proportional to the magnitude of the joint torque that creates it, directly proportional to the time of application of the joint torque, and inversely proportional to angular inertia of the rotating object. Thus, an increase in angular velocity is actually dependent on 3 factors:</span></div>
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<span style="font-family: Times, Times New Roman, serif;">an increase in the magnitude of the joint torque </span></div>
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<span style="font-family: Times, Times New Roman, serif;">an increase in the application time of the joint torque </span></div>
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<span style="font-family: Times, Times New Roman, serif;">a decrease in the angular inertia of the rotating object</span></div>
<div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-91808332988428631.post-50115685048067413002012-09-26T14:22:00.003-07:002012-09-26T14:31:53.660-07:00Forefoot Walking - The Research Findings that Support my BeliefSeveral of my students have adopted the forefoot walking technique. In their efforts to spread this information to their colleagues, friends, and clients they are encountering resistance. They are being challenged that what I am telling them is NOT supported by the research. So, I have put together a quick outline of the actual research findings (this is quoted material; I have done no paraphrasing) I reviewed when investigating walking techniques. I am sharing this with all of you in an effort to support your efforts to spread this information and to reduce people's resistance to accepting it. If your colleagues, friends, and clients still won't believe you, ask them for the "research" that supports their beliefs. Finally, I am always willing to talk with anyone about this topic. Share my email with them and ask them to contact me.<br />
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Click on this link to get the document: <a href="http://www.kin.sjsu.edu/faculty/jkao/Blog%20Documents/Forefoot%20Walking%20-%20Relevant%20Research.pdf">Forefoot Walking - Relevant Research</a><br />
<br /><div class="blogger-post-footer">Real World Biomechanics RSS Feed</div>Unknownnoreply@blogger.com2