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Below are comments in response to the following posting. The original posting is restated first.
Subject: [BIOMCH-L] Pose Running
We were interested in the recent post on Pose running and would like to try and spark a discussion on the topic. In no way are we trying to support or discount the possibility that the Pose method improves running technique by increasing speed or reducing injury.
In Dr Romanov's discussion paper on the Pose running technique (Romanov and Fetcher, 2007, Sport Biomechanics, 6, pp434-452), the authors state that they "hope to establish theoretically that gravity is the motive force in running...". The paper then argues from this perspective that other motive forces such as from muscles are relatively unimportant. The forces that act on the human body in motion include; (i) motion-dependent forces (from Coriolis and inertial effects), (ii) internal forces (principally from muscle), (iii) external forces (from ground, wind etc), and (iv) forces due to gravitational acceleration. Well-coordinated movement has also been shown to be characterized by the ability to adjust muscular forces to account for or to take advantage of motion-dependent, gravitational and external forces (e.g. Hollerbach et al 92; Schneider et al, 89 & 90; Ulrich et al 94). Running is likely no different from other well-coordinated body movements in that the runner or mover must account for and exploit the force environment in which they find themselves.
While gravitational acceleration might be particularly important in running, the external, motion-dependent and muscular forces can not be discounted as contributing to forward acceleration of the body. Zajac, Neptune and Kautz (2002, Gait and Posture, 17, pp1-17) review nicely how forward trunk acceleration receives marked contributions from lower extremity muscles, at least in walking. Romonov and Fetcher (2007) also state that extensor muscle activity ceases during mid stance and an extensor paradox arises. We have EMG on numerous good runners (national and international level) at running speeds of 6 to 9 m/s and we find ample EMG activity in late stance from muscle throughout the limb, including extensor muscles. Even without extensor muscles being active (which some are) forward acceleration of the trunk can arise from these 'non-extensor' muscles, although the magnitude of their contribution appears to be unknown for faster running.
It is certainly interesting to consider how good runners might exploit motion-dependent and gravitational forces (perhaps the Pose Technique promotes this), and how various muscles of the lower extremity contribute to the forward acceleration of the body's mass centre.
We would be interested in the thoughts of others.
Doug Rosemond, John Baker, Wayne Spratford, Alexi Sachlikidis, Sara Brice, Ami Drory, Nick Brown
Department of Biomechanics and Performance Analysis
Australian Institute of Sport
Canberra, Australia
Comments
I read the original article in Sport Biomechanics ...
Romanov and Fetcher, 2007, Sport Biomechanics, 6, pp434-452)
Our peer reviewed response to the original article and then the authors' final reply were published in the a later issue of Sport Biomechanics:
Brodie, M., Walmsley, A., Page W., 2008 Re: Runners do not push of the ground but fall forwards via Gravitational Torque, Letter to the editor. Journal of Sports Biomechanics, 7(03), pp. 403 - 405.
In regard to whether "gravity is the motive force in running", I strongly
disagree. First the vertical displacement of the CG is only about 4 cm in a
sprinter. This isn't sufficient distance to generate the forces seen in the
landing or pushoff. The force of the leg moving downward and backward at
touchdown is much more important.
The activity of the extensor muscles ceases in mid stance because the leg
undergoes flexion in the hip, knee and ankle joint to both absorb and to
withstand the landing forces. The pushoff occurs via ankle joint extension,
not hip extension.
For greater explanation of these comments and other details regarding
running mechanics I would like to refer you to my book, Explosive Running. I
incorporated all the latest biomechanical and kinesiological information
that I could find to explain what occurs in running at different speeds. It
was written in simple but very detailed terms for the coach and runner, to
explain and understand the latest scientific information.
It can be a good source for further discussion
I have found the Pose method to be full of falsehoods and misinformation.
Michael Yessis, Ph.D
Professor Emeritus, CSUF
President, Sports Training, Inc.
Regarding running form and adjustments, there is fairly substantial evidence suggesting that runners self-select stride parameters that are energetically optimal (Cavanagh & Williams, 1982; Hamill et al., 1995; Gutmann et al., 2006). Have any studies compared oxygen costs for forefoot vs. rearfoot running? I'd suspect that forefoot running is actually more costly due to a greater demand on the plantarflexors, at least for a natural rearfoot striker.
An important topic related to Romonov and Fletcher's recent study I think is the origin and interpretation of EMG signals. There are a number of nice review articles on this topic (Perry & Bekey, 1981; Kamen & Caldwell, 1996; Hof, 1997; Farina, 2006). Romonov and Fletcher cited references showing that extensor EMG are quiet in late stance and they concluded these muscle groups are producing no force at this time. First, this trend is not consistent across all studies, as Nick Brown pointed out. Second, EMG provides a measure of the action potentials delivered at the muscle fiber level, summed across the detectable motor units. It is not a measure of the relative force in the tendon, or the muscle's current capacity for force production, even if intramuscular electrodes are used. With electromechanical delays for de-activation of up to 100 ms (Vos et al., 1990; Hof, 1997), the cessation of a detectable EMG signal in late stance by no means indicates the target muscles are producing no force throughout this time.
Perturbation analyses of a walking simulation found that muscle forces, not gravity, accounted for the lion's share of the model's horizontal acceleration in late stance (Liu et al., 2006). I suspect that gravity would make a greater contribution during running, although the muscle forces would be much larger as well. While I agree that gravity contributes to horizontal COM acceleration in late stance, I think Romanov and Fletcher's main conclusion (that gravity is the only motive force in late stance) is overstated.
Ross
REFERENCES
Cavanagh PR and Williams KR (1982). The effect of stride length variation on oxygen uptake during distance running. Medicine and Science in Sports and Exercise, 14(1), 30-35.
Farina D (2006). Interpretation of the surface electromyogram in dynamic contractions. Exercise and Sport Sciences Reviews, 34(3), 121-127.
Gutmann AK, Jacobi B, Butcher MT, and Bertram JE (2006). Constrained optimization in human running. Journal of Experimental Biology, 209(4), 622-632.
Hamill J, Derrick TR, and Holt KG (1995). Shock attenuation and stride frequency during running. Human Movement Science, 14(1), 45-60.
Hof AL (1997). The relationship between electromyogram and muscle force. Sportverletzung Sportschaden, 11(3), 79-86.
Kamen G and Caldwell GE (1996). Physiology and interpretation of the electromyogram. Journal of Clinical Neurophysiology, 13(5), 366-384.
Liu MQ, Anderson FC, Pandy MG, and Delp SL (2006). Muscles that support the body also modulate forward progression during walking. Journal of Biomechanics, 39(14), 2623-2630.
Perry J and Bekey GA (1981). EMG-force relationships in skeletal muscle. Critical Reviews in BIomedical Engineering, 7(1), 1-22.
Vos EJ, Mullender MG, and van Ingen Schenau GJ (1990). Electromechanical delay in the vastus lateralis muscle during dynamic isometric contractions. European Journal of Applied Physiology and Occupational Physiology, 60(6), 467-471.
Ross Miller
I research foot mechanics and function. My work suggests that correcting pathomechanics improve performance is no small part because impact forces are transferred to the spine rather than dissipated. Serge Gracovetsky (The Spinal Engine) explained this phenomenon very nicely. The briefest summary of his work is that the body oscillates in the gravitational field. That is, we are designed to use gravity for ambulation rather than fight it. Thus, bipedal gait is cheaper than quadruped gait, and because of our foot configuration, bipedal gait is more efficient that facultative bipedal gait. (The great apes.) Gracovetsky has a huge volume of work. If you are not familiar with it, I am sure that it would shed light on your current investigation.
Regards,
Kevin Miller
It's interesting to note that in the Sport Biomechanics manuscript, the authors did not reference and discuss a study in which Romanov was a co-author (Journal of Sports Sciences 23(7):757-764, 2005.) This 12 week training protocol decreased stride length and increased sub-maximal oxygen, suggesting the Pose method had a negative effect on running performance.
The Pose method of running has been around for quite a few years now and basically is a technique where a runner is trained to run as a forefoot striker rather than a rearfoot striker (i.e. initial ground contact is coached to occur on the plantar forefoot rather than the plantar rearfoot). It seems to be based on the assumption that forefoot striking runners are less prone to injury, will run with more metabolic efficiency and will run faster. This is similar to another method of running that is also gaining popularity called Chi running that is also a forefoot striking running style.
As a sports podiatrist that has been treating runners for the past 23 years and from my background as a competetive distance runner, I am somewhat surprised that these two running techniques, which seem to be followed with a amazing zeal by the individuals that make a living teaching others how to run with the Pose and Chi method, have become so popular since I have seen many runners become injured in trying to adopt these running styles. Certainly some runners may benefit from a slight running style change but most long distance runners that I have known over the past 35 years have performed quite well in their rearfoot striking running patterns. Certainly at slower speeds of running, I would think that a rearfoot striking running pattern should remain the preferred foot contact pattern for most runners.
Kevin A. Kirby, DPM
I will try to add to the conversation from a clinical perspective. I will use an example of someone with medial tibial stress syndrome (MTSS, shin splints). One common clinical finding in those with MTSS is they tend to run with their center of gravity more posterior - so with each step they are eccentrically loading muscles such as the ant. tib. Clinically, one of the benefits of teaching these individuals to run using this technique is that it helps move their COG forward and decreases the eccentric demand on those muscles and is usually associated with a significant decrease in their symptoms.
It would be interesting to assess how the change in COG influences muscle activation during running with the Pose/Chi Running compared to a more upright posture.
Kindest Regards,
Deydre Teyhen
In regard to whether "gravity is the motive force in running", I strongly disagree. First the vertical displacement of the CG is only about 4 cm in a sprinter. This isn't sufficient distance to generate the forces seen in the landing or pushoff. The force of the leg moving downward and backward at touchdown is much more important.
The activity of the extensor muscles ceases in mid stance because the leg undergoes flexion in the hip, knee and ankle joint to both absorb and to withstand the landing forces. The pushoff occurs via ankle joint extension, not hip extension.
For greater explanation of these comments and other details regarding running mechanics I would like to refer you to my book, Explosive Running. I incorporated all the latest biomechanical and kinesiological information that I could find to explain what occurs in running at different speeds. It was written in simple but very detailed terms for the coach and runner, to explain and understand the latest scientific information.
It can be a good source for further discussion
I have found the Pose method to be full of falsehoods and misinformation.
Michael Yessis, Ph.D
I strongly believe that application of the leading joint hypothesis (LJH, Dounskaia 2005, Exp Brain Res, 166:1-16) would help to understand in detail the role of gravity, ground reaction forces, and muscular control in running. Zajac and colleagues suggested that during complex movement, each muscle can perform one of three functions, generation, transfer, or absorption of power. The LJH further specifies the role of various muscles during multi-joint movements. Namely, it states that the function of motion generation is limited to a single ("leading") joint (or, in some cases, a joint linkage spanned by bi-articular muscles). This joint is determined by its advantage in exploiting a mechanical effect driving the motion. The role of musculature at other joints is to regulate passive motion caused at them by motion-dependent (interaction) torques and external forces. We call these joints "subordinate" joints.
I have never had a chance to apply the LJH to locomotion. However, my guess is that during the stance phase, the ankle should be the leading joint responsible for generation of movement energy. It is quite possible that the ankle is used to propel the center of gravity forward to let gravitation to do the major work, as suggested by Romanov and Fletcher (2007). The role of the knee and hip muscles would be to regulate the effect of ankle motion. The goal of this regulation would, most probably, be balance maintenance. It may also be leg extension, but likely not to propel the body but rather to prepare the leg for its flexion that will be needed to soften the impact with the ground at the beginning of the next stance period.
I would expect that the analysis required to distinguish the leading and subordinate joints and the exact role of each is relatively simple, not like simulations performed by Zajac and colleagues. All torque components (muscle, interaction, gravitation torque, and torque caused by ground reaction forces) would need to be computed at each joint, and then the contribution of each to net torque would need to be analyzed, as we have been doing it for arm movements. Our studies show that this method helps to understand the global organization of control, the role of each joint in it, as well as subtle changes in joint control caused by aging or Parkinson's disease. Other authors have exploited this type of analysis to study differences in piano stroke performed by novice and expert pianists (Furuya & Kinoshita, 2008, Neuroscience, 156:390-402). Applied to running, this approach may be able to reveal differences in joint control between fast and slow runners and between different running techniques.
If anybody is interested to run this analysis, I would be happy to collaborate.
Natalia Dounskaia
First, in running all major joint actions do not occur simultaneously -- as
implied in the Pose method -- they occur in sequence. In essence there are
three leading actions, ankle extension in the pushoff, hip flexion in
driving the thigh forward and hip extension in driving the thigh down and
back to make ground contact.
During one joint action in which there may be transfer ? occurring
(concentric contraction) there is simultaneous generation ?(eccentric
contraction) of the antagonist muscles. I would also combine this with an
isometric contraction in some situations.
In running and in another sports, there may be some absorption initially but
the major purpose of the muscles is to withstand the forces in order to
return them (return of energy for greater efficiency. Thus the absorption
would take place in the eccentric contraction.
There is also a static (isometric) contractions of the adjacent joints to
stabilize the body and allow the single joint action to take place with
maximum effectiveness. I don't see how this would fit your model unless you
classify this as a passive action, which I do not. It is a very active
process.
Michael Yessis, Ph.D
-------------------------------------------------------------------------------------
Keep up to date with what's happening in Australian sport visit http://www.ausport.gov.au
This message is intended for the addressee named and may contain confidential and privileged information. If you are not the intended recipient please note that any form of distribution, copying or use of this communication or the information in it is strictly prohibited and may be unlawful. If you receive this message in error, please delete it and notify the sender.
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Subject: [BIOMCH-L] Pose Running
We were interested in the recent post on Pose running and would like to try and spark a discussion on the topic. In no way are we trying to support or discount the possibility that the Pose method improves running technique by increasing speed or reducing injury.
In Dr Romanov's discussion paper on the Pose running technique (Romanov and Fetcher, 2007, Sport Biomechanics, 6, pp434-452), the authors state that they "hope to establish theoretically that gravity is the motive force in running...". The paper then argues from this perspective that other motive forces such as from muscles are relatively unimportant. The forces that act on the human body in motion include; (i) motion-dependent forces (from Coriolis and inertial effects), (ii) internal forces (principally from muscle), (iii) external forces (from ground, wind etc), and (iv) forces due to gravitational acceleration. Well-coordinated movement has also been shown to be characterized by the ability to adjust muscular forces to account for or to take advantage of motion-dependent, gravitational and external forces (e.g. Hollerbach et al 92; Schneider et al, 89 & 90; Ulrich et al 94). Running is likely no different from other well-coordinated body movements in that the runner or mover must account for and exploit the force environment in which they find themselves.
While gravitational acceleration might be particularly important in running, the external, motion-dependent and muscular forces can not be discounted as contributing to forward acceleration of the body. Zajac, Neptune and Kautz (2002, Gait and Posture, 17, pp1-17) review nicely how forward trunk acceleration receives marked contributions from lower extremity muscles, at least in walking. Romonov and Fetcher (2007) also state that extensor muscle activity ceases during mid stance and an extensor paradox arises. We have EMG on numerous good runners (national and international level) at running speeds of 6 to 9 m/s and we find ample EMG activity in late stance from muscle throughout the limb, including extensor muscles. Even without extensor muscles being active (which some are) forward acceleration of the trunk can arise from these 'non-extensor' muscles, although the magnitude of their contribution appears to be unknown for faster running.
It is certainly interesting to consider how good runners might exploit motion-dependent and gravitational forces (perhaps the Pose Technique promotes this), and how various muscles of the lower extremity contribute to the forward acceleration of the body's mass centre.
We would be interested in the thoughts of others.
Doug Rosemond, John Baker, Wayne Spratford, Alexi Sachlikidis, Sara Brice, Ami Drory, Nick Brown
Department of Biomechanics and Performance Analysis
Australian Institute of Sport
Canberra, Australia
Comments
I read the original article in Sport Biomechanics ...
Romanov and Fetcher, 2007, Sport Biomechanics, 6, pp434-452)
Our peer reviewed response to the original article and then the authors' final reply were published in the a later issue of Sport Biomechanics:
Brodie, M., Walmsley, A., Page W., 2008 Re: Runners do not push of the ground but fall forwards via Gravitational Torque, Letter to the editor. Journal of Sports Biomechanics, 7(03), pp. 403 - 405.
In regard to whether "gravity is the motive force in running", I strongly
disagree. First the vertical displacement of the CG is only about 4 cm in a
sprinter. This isn't sufficient distance to generate the forces seen in the
landing or pushoff. The force of the leg moving downward and backward at
touchdown is much more important.
The activity of the extensor muscles ceases in mid stance because the leg
undergoes flexion in the hip, knee and ankle joint to both absorb and to
withstand the landing forces. The pushoff occurs via ankle joint extension,
not hip extension.
For greater explanation of these comments and other details regarding
running mechanics I would like to refer you to my book, Explosive Running. I
incorporated all the latest biomechanical and kinesiological information
that I could find to explain what occurs in running at different speeds. It
was written in simple but very detailed terms for the coach and runner, to
explain and understand the latest scientific information.
It can be a good source for further discussion
I have found the Pose method to be full of falsehoods and misinformation.
Michael Yessis, Ph.D
Professor Emeritus, CSUF
President, Sports Training, Inc.
Regarding running form and adjustments, there is fairly substantial evidence suggesting that runners self-select stride parameters that are energetically optimal (Cavanagh & Williams, 1982; Hamill et al., 1995; Gutmann et al., 2006). Have any studies compared oxygen costs for forefoot vs. rearfoot running? I'd suspect that forefoot running is actually more costly due to a greater demand on the plantarflexors, at least for a natural rearfoot striker.
An important topic related to Romonov and Fletcher's recent study I think is the origin and interpretation of EMG signals. There are a number of nice review articles on this topic (Perry & Bekey, 1981; Kamen & Caldwell, 1996; Hof, 1997; Farina, 2006). Romonov and Fletcher cited references showing that extensor EMG are quiet in late stance and they concluded these muscle groups are producing no force at this time. First, this trend is not consistent across all studies, as Nick Brown pointed out. Second, EMG provides a measure of the action potentials delivered at the muscle fiber level, summed across the detectable motor units. It is not a measure of the relative force in the tendon, or the muscle's current capacity for force production, even if intramuscular electrodes are used. With electromechanical delays for de-activation of up to 100 ms (Vos et al., 1990; Hof, 1997), the cessation of a detectable EMG signal in late stance by no means indicates the target muscles are producing no force throughout this time.
Perturbation analyses of a walking simulation found that muscle forces, not gravity, accounted for the lion's share of the model's horizontal acceleration in late stance (Liu et al., 2006). I suspect that gravity would make a greater contribution during running, although the muscle forces would be much larger as well. While I agree that gravity contributes to horizontal COM acceleration in late stance, I think Romanov and Fletcher's main conclusion (that gravity is the only motive force in late stance) is overstated.
Ross
REFERENCES
Cavanagh PR and Williams KR (1982). The effect of stride length variation on oxygen uptake during distance running. Medicine and Science in Sports and Exercise, 14(1), 30-35.
Farina D (2006). Interpretation of the surface electromyogram in dynamic contractions. Exercise and Sport Sciences Reviews, 34(3), 121-127.
Gutmann AK, Jacobi B, Butcher MT, and Bertram JE (2006). Constrained optimization in human running. Journal of Experimental Biology, 209(4), 622-632.
Hamill J, Derrick TR, and Holt KG (1995). Shock attenuation and stride frequency during running. Human Movement Science, 14(1), 45-60.
Hof AL (1997). The relationship between electromyogram and muscle force. Sportverletzung Sportschaden, 11(3), 79-86.
Kamen G and Caldwell GE (1996). Physiology and interpretation of the electromyogram. Journal of Clinical Neurophysiology, 13(5), 366-384.
Liu MQ, Anderson FC, Pandy MG, and Delp SL (2006). Muscles that support the body also modulate forward progression during walking. Journal of Biomechanics, 39(14), 2623-2630.
Perry J and Bekey GA (1981). EMG-force relationships in skeletal muscle. Critical Reviews in BIomedical Engineering, 7(1), 1-22.
Vos EJ, Mullender MG, and van Ingen Schenau GJ (1990). Electromechanical delay in the vastus lateralis muscle during dynamic isometric contractions. European Journal of Applied Physiology and Occupational Physiology, 60(6), 467-471.
Ross Miller
I research foot mechanics and function. My work suggests that correcting pathomechanics improve performance is no small part because impact forces are transferred to the spine rather than dissipated. Serge Gracovetsky (The Spinal Engine) explained this phenomenon very nicely. The briefest summary of his work is that the body oscillates in the gravitational field. That is, we are designed to use gravity for ambulation rather than fight it. Thus, bipedal gait is cheaper than quadruped gait, and because of our foot configuration, bipedal gait is more efficient that facultative bipedal gait. (The great apes.) Gracovetsky has a huge volume of work. If you are not familiar with it, I am sure that it would shed light on your current investigation.
Regards,
Kevin Miller
It's interesting to note that in the Sport Biomechanics manuscript, the authors did not reference and discuss a study in which Romanov was a co-author (Journal of Sports Sciences 23(7):757-764, 2005.) This 12 week training protocol decreased stride length and increased sub-maximal oxygen, suggesting the Pose method had a negative effect on running performance.
The Pose method of running has been around for quite a few years now and basically is a technique where a runner is trained to run as a forefoot striker rather than a rearfoot striker (i.e. initial ground contact is coached to occur on the plantar forefoot rather than the plantar rearfoot). It seems to be based on the assumption that forefoot striking runners are less prone to injury, will run with more metabolic efficiency and will run faster. This is similar to another method of running that is also gaining popularity called Chi running that is also a forefoot striking running style.
As a sports podiatrist that has been treating runners for the past 23 years and from my background as a competetive distance runner, I am somewhat surprised that these two running techniques, which seem to be followed with a amazing zeal by the individuals that make a living teaching others how to run with the Pose and Chi method, have become so popular since I have seen many runners become injured in trying to adopt these running styles. Certainly some runners may benefit from a slight running style change but most long distance runners that I have known over the past 35 years have performed quite well in their rearfoot striking running patterns. Certainly at slower speeds of running, I would think that a rearfoot striking running pattern should remain the preferred foot contact pattern for most runners.
Kevin A. Kirby, DPM
I will try to add to the conversation from a clinical perspective. I will use an example of someone with medial tibial stress syndrome (MTSS, shin splints). One common clinical finding in those with MTSS is they tend to run with their center of gravity more posterior - so with each step they are eccentrically loading muscles such as the ant. tib. Clinically, one of the benefits of teaching these individuals to run using this technique is that it helps move their COG forward and decreases the eccentric demand on those muscles and is usually associated with a significant decrease in their symptoms.
It would be interesting to assess how the change in COG influences muscle activation during running with the Pose/Chi Running compared to a more upright posture.
Kindest Regards,
Deydre Teyhen
In regard to whether "gravity is the motive force in running", I strongly disagree. First the vertical displacement of the CG is only about 4 cm in a sprinter. This isn't sufficient distance to generate the forces seen in the landing or pushoff. The force of the leg moving downward and backward at touchdown is much more important.
The activity of the extensor muscles ceases in mid stance because the leg undergoes flexion in the hip, knee and ankle joint to both absorb and to withstand the landing forces. The pushoff occurs via ankle joint extension, not hip extension.
For greater explanation of these comments and other details regarding running mechanics I would like to refer you to my book, Explosive Running. I incorporated all the latest biomechanical and kinesiological information that I could find to explain what occurs in running at different speeds. It was written in simple but very detailed terms for the coach and runner, to explain and understand the latest scientific information.
It can be a good source for further discussion
I have found the Pose method to be full of falsehoods and misinformation.
Michael Yessis, Ph.D
I strongly believe that application of the leading joint hypothesis (LJH, Dounskaia 2005, Exp Brain Res, 166:1-16) would help to understand in detail the role of gravity, ground reaction forces, and muscular control in running. Zajac and colleagues suggested that during complex movement, each muscle can perform one of three functions, generation, transfer, or absorption of power. The LJH further specifies the role of various muscles during multi-joint movements. Namely, it states that the function of motion generation is limited to a single ("leading") joint (or, in some cases, a joint linkage spanned by bi-articular muscles). This joint is determined by its advantage in exploiting a mechanical effect driving the motion. The role of musculature at other joints is to regulate passive motion caused at them by motion-dependent (interaction) torques and external forces. We call these joints "subordinate" joints.
I have never had a chance to apply the LJH to locomotion. However, my guess is that during the stance phase, the ankle should be the leading joint responsible for generation of movement energy. It is quite possible that the ankle is used to propel the center of gravity forward to let gravitation to do the major work, as suggested by Romanov and Fletcher (2007). The role of the knee and hip muscles would be to regulate the effect of ankle motion. The goal of this regulation would, most probably, be balance maintenance. It may also be leg extension, but likely not to propel the body but rather to prepare the leg for its flexion that will be needed to soften the impact with the ground at the beginning of the next stance period.
I would expect that the analysis required to distinguish the leading and subordinate joints and the exact role of each is relatively simple, not like simulations performed by Zajac and colleagues. All torque components (muscle, interaction, gravitation torque, and torque caused by ground reaction forces) would need to be computed at each joint, and then the contribution of each to net torque would need to be analyzed, as we have been doing it for arm movements. Our studies show that this method helps to understand the global organization of control, the role of each joint in it, as well as subtle changes in joint control caused by aging or Parkinson's disease. Other authors have exploited this type of analysis to study differences in piano stroke performed by novice and expert pianists (Furuya & Kinoshita, 2008, Neuroscience, 156:390-402). Applied to running, this approach may be able to reveal differences in joint control between fast and slow runners and between different running techniques.
If anybody is interested to run this analysis, I would be happy to collaborate.
Natalia Dounskaia
First, in running all major joint actions do not occur simultaneously -- as
implied in the Pose method -- they occur in sequence. In essence there are
three leading actions, ankle extension in the pushoff, hip flexion in
driving the thigh forward and hip extension in driving the thigh down and
back to make ground contact.
During one joint action in which there may be transfer ? occurring
(concentric contraction) there is simultaneous generation ?(eccentric
contraction) of the antagonist muscles. I would also combine this with an
isometric contraction in some situations.
In running and in another sports, there may be some absorption initially but
the major purpose of the muscles is to withstand the forces in order to
return them (return of energy for greater efficiency. Thus the absorption
would take place in the eccentric contraction.
There is also a static (isometric) contractions of the adjacent joints to
stabilize the body and allow the single joint action to take place with
maximum effectiveness. I don't see how this would fit your model unless you
classify this as a passive action, which I do not. It is a very active
process.
Michael Yessis, Ph.D
-------------------------------------------------------------------------------------
Keep up to date with what's happening in Australian sport visit http://www.ausport.gov.au
This message is intended for the addressee named and may contain confidential and privileged information. If you are not the intended recipient please note that any form of distribution, copying or use of this communication or the information in it is strictly prohibited and may be unlawful. If you receive this message in error, please delete it and notify the sender.
-------------------------------------------------------------------------------------