Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise

Goodall, Stuart, Thomas, Kevin, Barwood, Martin, Keane, Karen, Gonzalez, Javier, St Clair Gibson, Alan and Howatson, Glyn (2017) Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise. Acta Physiologica, 220 (4). pp. 486-800. ISSN 1748-1716

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Abstract

An initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise, however, the neuromuscular adaptions owing to this phenomenon are unknown.

Aim: To determine if neuromuscular disturbances are modulated following a repeated bout of eccentric exercise.

Methods: Following eccentric exercise performed with the elbow-flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase and voluntary activation using motor point and motor cortex stimulation at baseline, immediately post and at 1, 2, 3, 4 and 7 days post-exercise on two occasions, separated by 3 weeks.

Results: Significant muscle damage and fatigue was evident following the first exercise bout; maximal voluntary contraction was reduced immediately by 32% and remained depressed at 7 days post-exercise. Soreness and creatine kinase release peaked at 3 and 4 days post-exercise, respectively. Resting twitch force remained significantly reduced at 7 days (−48%) whilst voluntary activation measured with motor point and motor cortex stimulation was reduced until 2 and 3 days, respectively. A repeated bout effect was observed with attenuated soreness and creatine kinase release and a quicker recovery of maximal voluntary contraction and resting twitch force. A similar decrement in voluntary activation was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of voluntary activation measured using motor cortical stimulation.

Conclusion: Our data suggest that the repeated bout effect may be explained, partly, by a modification in motor corticospinal drive.

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