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Increased pain from muscle fascia following eccentric exercise: animal and human findings

PainSci » bibliography » Gibson et al 2009
updated
Tags: etiology, fascia, DOMS, pro, controversy, debunkery, massage, manual therapy, treatment, exercise, self-treatment, inflammation, pain problems, muscle

PainSci commentary on Gibson 2009: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

In a dozen people and some rates, soreness was induced by exercise and then the intensity of the soreness was measured. Subjects were injected with a salty solution both deep in the muscle as well as in the fibrous sheath around it. The superficial injections more painful than the deep ones, roughly double (about 5.6 compared to 3, on a 10-scale). Therefore, the authors speculate that “fascia rather than muscle tissue is important in DOMS associated sensitisation.” But the difference isn’t dramatic, and the injections in healthy muscle were almost exactly as painful as they were in sore muscle — so a more conservative interpretation isn’t “hurtin’ fascia is what causes DOMS” but rather “saline injections hurt!” But it is interesting and counter-intuitive that they hurt more when they are superficial injections.

~ Paul Ingraham

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

Mechanisms and structures which are involved in eccentric exercise-induced delayed onset muscle soreness (DOMS) are not yet clarified. Tissue and site specificity may be important considerations in afferent sensitisation following eccentric exercise. This study investigated the nociceptive response to hypertonic sodium solution applied to fascial/epimysium tissue and mechanically sensitised sites in muscle by assessing (1) afferent recordings in animals and (2) psychophysical assessment in humans. Seventeen male rats underwent eccentric contraction of extensor digitorum longus muscle, while 11 rats served as an unexercised naïve group. Two days post-exercise, group IV afferent fibre activity was recorded in response to superfusion of hypertonic Krebs solution on the mechanically sensitised muscle/epimysium site. Mechanical sensitisation was confirmed with significant increases in afferent response and decreases in threshold to mechanical stimulation in the eccentrically exercised rats compared to naïve rats. There was no difference in afferent response magnitude to hypertonic Krebs solution between exercise and naïve groups. In the human study, 13 volunteers participated. After bilateral assessment of pressure pain thresholds (PPT) along the tibialis anterior muscles, eccentric exercise was performed to induce DOMS in m. tibialis anterior of one leg. Site of maximal mechanical sensitivity was identified 24 h later and injected with hypertonic saline at fascial and deep muscle levels. The corresponding site on the opposite unexercised leg served as a control. Fascial injection of the exercised muscle caused significantly higher pain intensity compared to all other injections. Response to deep muscle stimulation was not different between sides. This suggests that fascia rather than muscle tissue is important in DOMS associated sensitisation.

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