Key result
Maximal eccentric exercise reduced short-interval intracortical inhibition by 27% in resting and 23% in active biceps brachii muscle 2 hours after exercise.
Why the study?
Does maximal eccentric exercise reduce short-interval intracortical inhibition in young male subjects?
Does maximal eccentric exercise reduce short-interval intracortical inhibition in young male subjects?
Effect estimate: 27% reduction in resting and 23% reduction in active muscle
Eccentric muscle damage transiently reduces short-interval intracortical inhibition 2 hours post-exercise, suggesting widespread effects throughout the motor system including the motor cortex.
Indicates motor cortical changes after eccentric exercise; leaves open relevance to recovery or performance in clinical populations.
The purpose of this study was to use paired-pulse transcranial magnetic stimulation (TMS) to examine the effect of eccentric exercise on short-interval intracortical inhibition (SICI) after damage to elbow flexor muscles. Nine young (22.5 ± 0.6 yr; mean ± SD) male subjects performed maximal eccentric exercise of the elbow flexor muscles until maximal voluntary contraction (MVC) force was reduced by ∼40%. TMS was performed before, 2 h after, and 2 days after exercise under Rest and Active (5% MVC) conditions with motor-evoked potentials (MEPs) recorded from the biceps brachii (BB) muscle. Peripheral electrical stimulation of the brachial plexus was used to assess maximal M-waves, and paired-pulse TMS with a 3-ms interstimulus interval was used to assess changes in SICI at each time point. The eccentric exercise resulted in a 34% decline in strength (P < 0.001), a 41% decline in resting M-wave (P = 0.01), changes in resting elbow joint angle (10°, P < 0.001), and a shift in the optimal elbow joint angle for force production (18°, P < 0.05) 2 h after exercise. This was accompanied by impaired muscle strength (27%, P < 0.001) and increased muscle soreness (P < 0.001) 2 days after exercise, which is indicative of muscle damage. When the test MEP amplitudes were matched between sessions, we found that SICI was reduced by 27% in resting and 23% in active BB muscle 2 h after exercise. SICI recovered 2 days after exercise when muscle pain and soreness were present, suggesting that delayed onset muscle soreness from eccentric exercise does not influence SICI. The change in SICI observed 2 h after exercise suggests that eccentric muscle damage has widespread effects throughout the motor system that likely includes changes in motor cortex.
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Pitman et al. (2012) studied this question. Maximal eccentric exercise of the elbow flexor muscles vs. Baseline (before exercise) was evaluated on Short-interval intracortical inhibition (SICI) 2 hours after exercise (27% reduction in resting and 23% reduction in active muscle). Maximal eccentric exercise reduced short-interval intracortical inhibition by 27% in resting and 23% in active biceps brachii muscle 2 hours after exercise.
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