Podcast 148: A deep dive case study. Plus, Central and Peripheral fatigue explained

tag/key words: gait, gaitproblems, gaitanalysis, forefootrunning, forefootstrike, heelstrike, pronation, central fatigue, peripheral fatigue, fatigue, hip rotation, gait biomechanics, running

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"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