Delayed-Onset Muscle Soreness and Topical Analgesic Alter Corticospinal Excitability of the Biceps Brachii

Abstract

Introduction The interactive effect of delayed-onset muscle soreness (DOMS) and a topical analgesic on corticospinal excitability was investigated. Methods Thirty-two participants completed Experiments A (no DOMS) and B (DOMS). For each experiment, participants were randomly assigned to two groups: 1) topical analgesic gel (topical analgesic, n = 8), or 2) placebo gel (placebo, n = 8) group. Before the application of gel (pregel), as well as 5, 15, 30, and 45 min postgel, motor-evoked potential (MEP) area, latency, and silent period, as well as cervicomedullary MEP and maximal compound motor unit action potential areas and latencies were measured. In addition, pressure–pain threshold (PPT) was measured pre-DOMS and at the same timepoints in experiment B. Results In experiment A, neither group showed a significant change for any outcome measure. In experiment B, both groups exhibited a significant decrease in PPT from pre-DOMS to pregel. After the application of topical analgesic, but not placebo, there was a significant increase in PPT at 45 min postgel, respectively, compared with pregel and a main effect of time for the silent period to increase compared with pregel. Participants with DOMS had reduced MEP and cervicomedullary MEP areas and increased corticospinal silent periods compared with those who did not have DOMS. Conclusions These findings suggest that DOMS reduced corticospinal excitability and after the administration of menthol-based topical analgesic, there was a reduction in pain, which was accompanied by increased corticospinal inhibition.

Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans

“…Using M max for normalization purposes during dynamic motor outputs has several advantages. The amplitude of the M max is reproducible both within (24,28,31,34,92) and between experimental days (93); during a range of isometric and dynamic contraction intensities (24,28,31,34,92); before, during, and following fatiguing contractions (94)(95)(96); in the presence of pain (30); and in the presence of hyperthermia (97) and hypothermia (98). Interestingly, in all of the aforementioned studies (except one, vastus lateralis), the M max was elicited in the biceps brachii.…”

“…During dynamic motor outputs, a supramaximal electrical stimulus is applied to a nerve to evoke a maximal M-wave (M max ), which represents the summation of the electrical activity of the motor units activated by the electrical stimulus (22). The main role of the M max in relation to quantifying central nervous system excitability during dynamic motor outputs is for normalization purposes (23)(24)(25)(26)(27)(28)(29)(30). Because the electrical stimulus that elicits the M max occurs outside of the central nervous system pathways, it should not reflect changes in excitability that occur centrally.…”

Spinal and corticospinal excitability in response to reductions in skin and core temperatures via whole-body cooling

“…For both trials, muscle EMG was measured with disposable self-adhesive bipolar Ag/AgCl surface electrodes (Meditrace, Kendall, Mansidel, MA, USA) affixed to the skin over the muscle belly 2 cm apart (centre to centre). Skin preparation for all electrodes followed accepted practices (Stefanelli et al 2019). Briefly, hair was removed by shaving the skin, and the skin was abraded with fine grit sandpaper and further cleaned with a 70% isopropyl alcohol wipe.…”

“…EMG signals were sampled at 1 KHz during the MVCs and the 8-min EMG blocks used to assess shivering activity (Blondin et al 2017;Haman 2004;Imbeault, Mantha and Haman 2013). EMG signals were sampled at 5 KHz during stimulation blocks (Stefanelli et al 2019).…”

Neuromuscular Mechanisms Underlying Changes in Force Production during an Attentional Focus Task

“…The vertex was located by marking the measured halfway points between the nasion to inion and tragus to tragus. The coil was flipped to ensure the induced current flow was anterior to posterior in the target motor cortex (A side up for right side, B side up for left) to activate the dominant biceps brachii [29][30][31]. The optimum stimulation site was determined by initially placing the coil over the vertex and slightly moving the coil towards the non-dominant hemisphere in three directions, i.e., anteriorly, posteriorly, and laterally.…”