Fatigue and exercise.

Do your clients do their home program exercise before activity ? We warn our clients about fatigue/endurance all the time. We will build capacity and durability on skills before we hit strength parameters all the time. We like to ensure that we get a durable pattern engrained before we challenge it with more strength challenges.
*However, do not let your clients do their home program to fatigue before activity. It is ok to prime the movement patterns with corrective exercise, but just a few reps before activity. This study suggests why:
“We conclude that 20min is not enough to see full recovery of gait after exhaustive quadriceps muscle fatigue.”-Barbieri FA et al.

addendum:  Keep in mind, that during exercise, say a 7 mile run, if you fatigue some critical joint stabilizers at the 5 mile mark, ……. you will begin to run a comensatory sub-motor program.  You hope !   Just don;t do that too often !  How do  you know ?  You don’t, until you get pain from that pattern failing quite possibly !

Gait Posture. 2016 Jan;43:270-4. doi: 10.1016/j.gaitpost.2015.10.015. Epub 2015 Oct 25.Recovery of gait after quadriceps muscle fatigue.Barbieri FA1, Beretta SS2, Pereira VA3, Simieli L2, Orcioli-Silva D2, Dos Santos PC2, van Dieën JH4, Gobbi LT2.


We always like to try and reproduce the problem. We like to say “If we can reproduce the pain, we can probably fix the cause”, which seems to hold true in many cases. This article makes us think about seeing the patient at a point in their training that they feel the discomfort or are having the problem (after 30 minutes, after 20 miles, etc). There may be some value to scheduling their exam later, rather than sooner. A nice fatigue article from one of our favs “LER”.


The effect of lower extremity fatigue on shock attenuation during single-leg landing.

Thank goodness the body can compensate. Here is a perfect example of this discussed in this study.
“ … it has been shown that a fatigued muscle decreases the body’s ability to attenuate shock from running. The purpose of the study was to determine the effect of lower extremity fatigue on shock attenuation and joint mechanics during a single-leg drop landing.”
This study suggests that as one part fatigued, the joint and muscle strategies elsewhere in the limb made up for it.
“Hip and knee flexion increased and ankle plantarflexion decreased at touchdown with fatigue. Hip joint work increased and ankle work decreased.” The results suggested that the lower extremity is able to adapt to fatigue though altering kinematics at impact and redistributing work to larger proximal muscles.

The effect of lower extremity fatigue on shock attenuation during single-leg landing. Clin Biomech (Bristol, Avon). 2006 Dec;21(10):1090-7. Epub 2006 Sep 1.
Coventry E1, O’Connor KM, Hart BA, Earl JE, Ebersole KT.

“Postures must have integrity. Patterns must have economy.”

We love Gray Cook’s memes.

“Postures must have integrity.  Patterns must have economy.”

This one is a keeper…….we would like to add that “patterns must have economy AND capacity”.

We have talked about central fatigue here on FB and our blog, and it has alluded to the fact that neuromuscular motor patterns are driven centrally from the CPG’s (central pattern generators in a few areas of the brain). Metabolic capacity problems can alter motor patterns, so fatigue can come centrally as well as peripherally at the muscle, which we typically think of when we think of fatigue. The brain has a metabolic demand as well, and if it hits a “fuel” limitation (cerebral hypometabolism) the movement driven from that path will be corrupt. Craig Liebenson refers to muscle “amnesia”, perhaps this is what he is alluding to, it is a central fuel capacity fatigue issue to be more precise. Here at The Gait Guys we like to say you better have S.E.S. (skill, endurance, strength). The endurance is a local and a central fuel endurance thing. Thanks Gray ! Move well, move often.

Shawn and Ivo

the gait guys


“Human muscle fatigue does not simply reside in the muscle”.

So you like to “activate” clients muscles huh? Its the big flashy trend right now done by some folks who know very little about what they are doing and perhaps adding risk to athletes right before an event or practice.
How much do you really know what you are doing ?
Have you heard of “central fatigue” and the neural mechanisms underlying it? Do you think that merely “activating” your client will make them safe and perform better on the field ? What if it added even more risk to their system ? If you are only driving the changes at the end organ, the muscles and their receptors, you may not even be half way there. Read on … .

“Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline.Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal changes in cortical excitability and inhibitability based on electromyographic (EMG) recordings, and a decline in supraspinal “drive” based on force recordings. Some of the changes in motor cortical behavior can be dissociated from the development of this “supraspinal” fatigue. Central changes also occur at a spinal level due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. Some intrinsic adaptive properties of the motoneurons help to minimize fatigue. A number of other central changes occur during fatigue and affect, for example, proprioception, tremor, and postural control. Human muscle fatigue does not simply reside in the muscle.”

Hopefully stuff like this ruffles some feathers, raises eyebrows and questions, starts deeper meaningful dialogues, forces people to understand their scope and pay grade, and forces us all to ask harder questions especially when things seems easy and too good to be true. There is no finger pointing here dear brethren, so no need to retaliate or raise up arms to defend a position. Just read the research and ask yourself the tough questions…… “am i part of the solution, or part of the problem”? We can all do better, lets all raise up and step up, and elevate the professions together. It can only make it better for those that need it, our clients and patients.

Physiol Rev. 2001 Oct;81(4):1725-89.
Spinal and supraspinal factors in human muscle fatigue.
Gandevia SC


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.


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


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.