Post Contraction Sensory Discharge

Do you have clients who just can't move very well?

Do they seem to stretch regularly but they still don't improve their posture or movement?

Do you wish someone could show you something new that can help YOU help MORE people improve the way they move?

Did you know that not all muscles need stretching?

Did you know that more often than not muscles require a contraction to improve there function?

Ever heard of subclinical muscle spasm?

Ever heard of Post Contraction Sensory Discharge?

Question: What is muscle spasm? …’A muscle that cannot relax’ Jiri Dorvak and Ribot-Ciscar: 

1. The anti-spasm or 20/20 work as we refer to it now as its simpler for the end user (20% effort muscle contraction held for 20 seconds) is described by Jiri Dorvak who is a professor of neurology and is CMO for FIFA. He has established that a muscle relaxes maximally after it has been contracted sub-maximally and for a prolonged period. He refers to it as Post Contraction Sensory Discharge. 

2. More work has been carried out by Ribot-Ciscar and colleagues, abstract below........ 

E. Ribot-Ciscar, M. F. Tardy-Gervet, J. P. Vedel and J. P. Roll 

Summary “The activities of human muscle spindle primary endings were recorded in the lateral peroneal nerve using the microneurographic method. The aim of the study was to test whether voluntary isometric contraction causes any after-effects, first in the resting discharge of muscle spindle primary endings and secondly in their responses to a slow ramp stretch. To investigate the latter point, the initial angular position of the ankle was passively adjusted until the unit fell silent, in order to introduce a delay in the responses to muscle stretch”....they found that “Isometric voluntary contraction led to changes in muscle spindle stretch sensitivity which resulted in a reduction in the stretch threshold and a decrease in the muscle spindle dynamic sensitivity. These data suggest that the after-effects observed may have been triggered by static fusimotor neurones. The results are discussed with reference to the theory according to which the processing by the CNS of muscular proprioceptive messages deals mainly with signals arising from muscles stretched during movement, and it is concluded that the coactivation of and y motoneurones during the contraction facilitates the coding of the parameters of forthcoming stretching movements, by the muscle spindles”. 

So in other words the 20/20 or anti-spasm exercises like the 4 Sign or Leg Press, allow the muscle to stretch easier after the ‘contraction’, and consequently improves the function of the muscle. 

No single method will help all ‘types’ of spasm of course, this is one of many ways that can help, including trigger points, soft tissue massage etc too. What it is though, is a great way to provide your clients with a way that they can help themselves so they’re don’t become reliant on their therapist or trainer. It’s something to empower them to contribute their own problems between sessions with you or their therapist. 

What it is?: A muscle in spasm is one that cannot relax in other words it is in a state of constant contraction (tension).

Why?: Usually because it’s trying to protect something (a joint or nerve perhaps) or its being loaded from another biomechanical problem remote from that muscle. 

Management?: Helped by anti-spasm exercises (20/20) and massage techniques. 

What it is?: A short/inflexible muscle (tight) is one that is not in spasm, it is merely shorter in length than it was intended (or needs) to be.

Why?: Often adaptive shortening caused by adapting to inactivity, lack of use through full range, poor posture or poor technique. 

Management?: Helped by stretching techniques, some massage techniques may also help. 

What is it?: ‘Knots’ or ‘trigger points’

Why?: Generally those muscles that have been in spasm for a long time and the muscle has adapted its structure and become fibrotic to save energy. Tardeau and Tarbury in the late 90’s found that up to 40% of a muscle can change its composition if its been in spasm for more than 6 weeks to become more tendon-like (none contractile) to avoid the muscle having to exert energy to contract the muscle to protect (a joint for example). If the muscle is fibrotic, it requires less effort and therefore is less susceptible to fatigue, it is a body’s way of compensating and being ‘efficient’; not always productive or effective though as its painful of course. 

Management?: This can helped by trigger point work and other techniques. 

Finally..

As for the muscle spasm information, Jiri Dorvak and Robot-Ciscar both refer to a muscle relaxing optimally after a prolonged sub maximal contractions. Dorvak refers to Post Contraction Sensory Discharge. Robot-Ciscar looked at human muscle spindle primary endings to test whether voluntary isometric contraction causes any after-effects, first in the resting discharge of muscle spindle primary endings and secondly in their responses to a slow ramp stretch. This physiology has not been shown to be present in a ‘tight’ muscle. 

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