On the topic of endurance training…..

On the topic of endurance training (which we discussed on this weeks PODcast, forthcoming in the next day or so; we have both been extraordinarily busy in our clinics); if you are a well trained athlete (ie endurance junkie), how might this effect your running gait?

So, you run 103 miles with an elevation change of over 31,000 feet, how do you think you would fare? These folks were tested pre and 3 hours post race on a 22 foot long pressure walkway at about 7.5 miles per hour. Here’s how this group of 18 folks did:

  1. increased step frequency
  2. decreased “aerial” time
  3. no change in contact time
  4. decrease in downward displacement of the center of mass
  5. decrease in peak vertical ground reactive force
  6. increased vertical oscillation
  7. leg stiffness remained unchanged

So what does this tell us?

  • wow, that is a lot of vertical
  • holy smokes, that is really far
  • don’t know how I would do with a race like that
  • they are fatigued (1, 2, 6)
  • they are trying to attenuate impact forces (2, 3, 4, 5, 7)

The system is trying to adapt the best it can. If you were to do a standard hip screen test (like we spoke about here)  you would probably see increased horizontal drift due to proprioceptive fatigue. Remember that proprioception (our bodies ability to sense its position in space) makes the world go round. Proprioception is dependent on an intact visual system (see our post yesterday) , an intact vestibular system and muscle and joint mechanoreceptors functioning appropriately). We would add here that central nervous system fatigue (ie central processing both at the cord and in the cortex) would probably play a role as well.

The take home message? The human machine is a neuro mechanical marvel and much more complex than having the right shoe or the right running technique. Training often makes us more competent and efficient, but everything has it limits.

The Gait Guys. Making it real with each and every post.

all material copyright 2013 The Gait Guys/ The Homunculus Group

J Biomech. 2011 Apr 7;44(6):1104-7. doi: 10.1016/j.jbiomech.2011.01.028. Epub 2011 Feb 20.

Changes in running mechanics and spring-mass behavior induced by a mountain ultra-marathon race.

Source

Université de Lyon, F-42023 Saint-Etienne, France. jean.benoit.morin@univ-st-etienne.fr

Abstract

Changes in running mechanics and spring-mass behavior due to fatigue induced by a mountain ultra-marathon race (MUM, 166km, total positive and negative elevation of 9500m) were studied in 18 ultra-marathon runners. Mechanical measurements were undertaken pre- and 3h post-MUM at 12km h(-1) on a 7m long pressure walkway: contact (t(c)), aerial (t(a)) times, step frequency (f), and running velocity (v) were sampled and averaged over 5-8 steps. From these variables, spring-mass parameters of peak vertical ground reaction force (F(max)), vertical downward displacement of the center of mass (Δz), leg length change (ΔL), vertical (k(vert)) and leg (k(leg)) stiffness were computed. After the MUM, there was a significant increase in f (5.9±5.5%; P<0.001) associated with reduced t(a) (-18.5±17.4%; P<0.001) with no change in t(c), and a significant decrease in both Δz and F(max) (-11.6±10.5 and -6.3±7.3%, respectively; P<0.001). k(vert) increased by 5.6±11.7% (P=0.053), and k(leg) remained unchanged. These results show that 3h post-MUM, subjects ran with a reduced vertical oscillation of their spring-mass system. This is consistent with (i) previous studies concerning muscular structure/function impairment in running and (ii) the hypothesis that these changes in the running pattern could be associated with lower overall impact (especially during the braking phase) supported by the locomotor system at each step, potentially leading to reduced pain during running.

Copyright © 2011 Elsevier Ltd. All rights reserved.

http://www.ncbi.nlm.nih.gov/pubmed/21342691

Podcast #27: Futuristic Gait & Vertical Oscillations

 Pod #27

podcast link: 

http://thegaitguys.libsyn.com/pod-27-futuristic-gait-vertical-oscillations

iTunes link:

https://itunes.apple.com/us/podcast/the-gait-guys-podcast/id559864138

Gait Guys online /download store:

http://store.payloadz.com/results/results.aspx?m=80204

other web based Gait Guys lectures:

www.onlinece.com   type in Dr. Waerlop or Dr. Allen  Biomechanics

Today’s show notes:

1. Neuroscience Piece:

http://www.designnews.com/author.asp?section_id=1386&itc=dn_analysis_element&doc_id=254901&page_number=1&dfpPParams=ind_182,industry_medical,aid_254901&dfpLayout=blog

Six months after doctors told him he would likely never walk again after a random accident at home, 49-year-old Chris Tagatac was back on his feet and taking steps, a feat that elated not only him, but also his family.

Tagatac didn’t accomplish this feat on his own, however. He was walking with the help of Ekso, a wearable robot from a company called Ekso Bionics that consists of braces, sensors, and motors that anticipate people’s movements and take steps for them.


2- NEURO 2
http://reuters.tumblr.com/post/46251254817/for-the-first-time-scientists-have-printed-human


For the first time scientists have printed human embryonic stem cells using a 3D printer

The Heriot-Watt University team’s research could eventually lead to human organs being printed on demand and an end to animal drug testing. Jim Drury reports.

 

3. Vertical Oscilations, Danny Abshire and Running & Walking

https://www.facebook.com/photo.php?v=575995729092248&set=vb.111772995514526&type=2&theater

This study’s findings findings clearly demonstrate that human walkers consume substantially more metabolic energy when they minimize vertical motion.

Anyhow, the summary of this peer reviewed article by Ortega concluded that :

“in flat-trajectory walking, subjects reduced center of mass vertical displacement by an average of 69% but consumed approximately twice as much metabolic energy over a range of speeds . In flat-trajectory walking, passive pendulum-like mechanical energy exchange provided only a small portion of the energy required to accelerate the center of mass because gravitational potential energy fluctuated minimally. Thus, despite the smaller vertical movements in flat-trajectory walking, the net external mechanical work needed to move the center of mass was similar in both types of walking. Subjects walked with more flexed stance limbs in flat-trajectory walking, and the resultant increase in stance limb force generation likely helped cause the doubling in metabolic cost compared with normal walking. Regardless of the cause, these findings clearly demonstrate that human walkers consume substantially more metabolic energy when they minimize vertical motion.”

J Appl Physiol. 2005 Dec;99(6):2099-107. Epub 2005 Jul 28. Minimizing center of mass vertical movement increases metabolic cost in walking. Ortega JD, Farley CT. Source



J Sports Sci. 2005 Jul;23(7):757-64.

Effect of a global alteration of running technique on kinematics and economy.



J Biomech. 2011 Apr 7;44(6):1104-7. doi: 10.1016/j.jbiomech.2011.01.
028. Epub 2011 Feb 20.

Changes in running mechanics and spring-mass behavior induced by a mountain ultra-marathon race.


http://www.technologyreview.com/view/413593/revealing-the-secrets-of-human-gait/

Revealing the secrets of human gait

A simple measure of the forces involved in walking may help diagnose and treat injuries and arthritis

So the work of Yifang Fan and pals at Jinan University in China is a refreshing step forward (so to speak). Fan and co say they have discovered an independent measure of gait which they call the vertical gait reaction force. This is a measure of the amount by which a person’s centre of gravity raises during two complete steps (with the left and then the right foot).

In healthy adults, and Fan and co have tested 173, this force is symmetrical with regard to left and right foot, a finding they call the principle of least action (in other words, the body does no more than it has to move you around). That’s useful, they say, because no other measure gives this kind of symmetric signal for all healthy people.

In adults carrying an ankle injury or with arthritis, the pattern of force is not symmetrical. That allows a quick diagnosis simply by measuring this force and may in future point to the type of rehabilitation that may treat the condition.

_____________
4. Shoe: NB minimus (the new one) and the HI-REZ

http://www.newbalance.com/Minimus-Hi-Rez-Where-Science-Meets-Design/article_minimus_hirez_where_science_meets_design,default,pg.html___________________

 Shawn and Ivo, The Gait Guys

 

Podcast #27: Futuristic Gait & Vertical Oscillations

 Pod #27

podcast link: 

http://thegaitguys.libsyn.com/pod-27-futuristic-gait-vertical-oscillations

iTunes link:

https://itunes.apple.com/us/podcast/the-gait-guys-podcast/id559864138

Gait Guys online /download store:

http://store.payloadz.com/results/results.aspx?m=80204

other web based Gait Guys lectures:

www.onlinece.com   type in Dr. Waerlop or Dr. Allen  Biomechanics

Today’s show notes:

1. Neuroscience Piece:

http://www.designnews.com/author.asp?section_id=1386&itc=dn_analysis_element&doc_id=254901&page_number=1&dfpPParams=ind_182,industry_medical,aid_254901&dfpLayout=blog

Six months after doctors told him he would likely never walk again after a random accident at home, 49-year-old Chris Tagatac was back on his feet and taking steps, a feat that elated not only him, but also his family.

Tagatac didn’t accomplish this feat on his own, however. He was walking with the help of Ekso, a wearable robot from a company called Ekso Bionics that consists of braces, sensors, and motors that anticipate people’s movements and take steps for them.


2- NEURO 2
http://reuters.tumblr.com/post/46251254817/for-the-first-time-scientists-have-printed-human


For the first time scientists have printed human embryonic stem cells using a 3D printer

The Heriot-Watt University team’s research could eventually lead to human organs being printed on demand and an end to animal drug testing. Jim Drury reports.

 

3. Vertical Oscilations, Danny Abshire and Running & Walking

https://www.facebook.com/photo.php?v=575995729092248&set=vb.111772995514526&type=2&theater

This study’s findings findings clearly demonstrate that human walkers consume substantially more metabolic energy when they minimize vertical motion.

Anyhow, the summary of this peer reviewed article by Ortega concluded that :

“in flat-trajectory walking, subjects reduced center of mass vertical displacement by an average of 69% but consumed approximately twice as much metabolic energy over a range of speeds . In flat-trajectory walking, passive pendulum-like mechanical energy exchange provided only a small portion of the energy required to accelerate the center of mass because gravitational potential energy fluctuated minimally. Thus, despite the smaller vertical movements in flat-trajectory walking, the net external mechanical work needed to move the center of mass was similar in both types of walking. Subjects walked with more flexed stance limbs in flat-trajectory walking, and the resultant increase in stance limb force generation likely helped cause the doubling in metabolic cost compared with normal walking. Regardless of the cause, these findings clearly demonstrate that human walkers consume substantially more metabolic energy when they minimize vertical motion.”

J Appl Physiol. 2005 Dec;99(6):2099-107. Epub 2005 Jul 28. Minimizing center of mass vertical movement increases metabolic cost in walking. Ortega JD, Farley CT. Source



J Sports Sci. 2005 Jul;23(7):757-64.

Effect of a global alteration of running technique on kinematics and economy.



J Biomech. 2011 Apr 7;44(6):1104-7. doi: 10.1016/j.jbiomech.2011.01.
028. Epub 2011 Feb 20.

Changes in running mechanics and spring-mass behavior induced by a mountain ultra-marathon race.


http://www.technologyreview.com/view/413593/revealing-the-secrets-of-human-gait/

Revealing the secrets of human gait

A simple measure of the forces involved in walking may help diagnose and treat injuries and arthritis

So the work of Yifang Fan and pals at Jinan University in China is a refreshing step forward (so to speak). Fan and co say they have discovered an independent measure of gait which they call the vertical gait reaction force. This is a measure of the amount by which a person’s centre of gravity raises during two complete steps (with the left and then the right foot).

In healthy adults, and Fan and co have tested 173, this force is symmetrical with regard to left and right foot, a finding they call the principle of least action (in other words, the body does no more than it has to move you around). That’s useful, they say, because no other measure gives this kind of symmetric signal for all healthy people.

In adults carrying an ankle injury or with arthritis, the pattern of force is not symmetrical. That allows a quick diagnosis simply by measuring this force and may in future point to the type of rehabilitation that may treat the condition.

_____________
4. Shoe: NB minimus (the new one) and the HI-REZ

http://www.newbalance.com/Minimus-Hi-Rez-Where-Science-Meets-Design/article_minimus_hirez_where_science_meets_design,default,pg.html___________________

 Shawn and Ivo, The Gait Guys