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:
- increased step frequency
- decreased “aerial” time
- no change in contact time
- decrease in downward displacement of the center of mass
- decrease in peak vertical ground reactive force
- increased vertical oscillation
- 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
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©), 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©, 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.
