The short-term recovery of corticomotor responses in elbow flexors

Abstract

BackgroundThe recovery of neurophysiological parameters at various time intervals following fatiguing exercise has been investigated previously. However, the repetition of neuromuscular assessments during the recovery period may have interfered with the true corticomotor excitability responses. In this experiment, fatiguing contractions were combined with a single post-fatigue assessment at varying time points. Ten participants undertook 5 bouts of 60-s maximal voluntary contractions (MVC) of the elbow flexors, separated by 20 min. Before and after each 60-s fatiguing exercise (FAT), participants performed a series of 6-s contractions at 100, 75 and 50% of their MVC during which transcranial magnetic, transmastoid electrical and brachial plexus electrical stimuli were used to elicit motor evoked potentials (MEP), cervicomedullary motor evoked potentials (CMEP) and compound muscle action potentials (Mmax) in the biceps brachii muscle, respectively. Post-FAT measurements were randomly performed 0, 15, 30, 60, or 120 s after each FAT.ResultsMVC force declined to 65.1 ± 13.1% of baseline following FAT and then recovered to 82.7 ± 10.2% after 60 s. The MEP·Mmax−1 ratio recorded at MVC increased to 151.1 ± 45.8% and then returned to baseline within 60 s. The supraspinal excitability (MEP·CMEP−1) measured at MVC increased to 198.2 ± 47.2% and fully recovered after 30 s. The duration of post-MEP silent period recorded at MVC elongated by 23.4 ± 10.6% during FAT (all P < 0.05) but fully recovered after 15 s.ConclusionsThe current study represents the first accurate description of the time course and pattern of recovery for supraspinal and spinal excitability and inhibition following a short maximal fatiguing exercise in upper limb.

The Effect of Fatigue on Single-Leg Postural Sway and Its Transient Characteristics in Healthy Young Adults

“…Indeed, postural sway assessed through CoP movements is highly variable, and coefficient of variation >10% is often observed ( Hébert-Losier and Murray, 2020 ). We used one repetition in our protocol because the fatigue could subside quickly after the completion of the fatiguing protocol ( Aboodarda et al, 2019 ; Güler et al, 2020 ). Nevertheless, more repetitions should be used prior to the fatiguing protocol to increase the rigor of the results.…”

Neuromuscular responses to fatiguing locomotor exercise

“…Similarly conflicting results have been shown for the silent period, with no change 113 or an increase 18 being reported. The conflicting findings could be the result of the substantial heterogeneity in the exercise challenges, such as the modalities and the duration of the task, as well as methodological differences such as stimulation intensities and the contraction intensities at which corticospinal excitability is measured, both of which can influence the change in MEP in response to exercise 18,143 . No research to date has utilised spinal stimulation to assess the effect of prolonged exercise on α‐motoneuron excitability, and this represents an area for future research.…”

Strength and Electromyographic Responses of Upper and Lower Limbs During Maximal Intermittent Contractions in Males and Females

“…In addition, the elbow flexors incur greater contractile disturbance than the knee extensors (35,37). It may be that during the current fatigue protocol, the 30-second recovery intervals were long enough for supraspinal and corticospinal disruptions to recover (1). In addition, owing to this relatively long rest interval, the muscle-related difference in peripheral fatigue might not be as obvious as it would be in protocols with shorter rest intervals (e.g., less than 10 seconds).…”

“…Recovery interval duration directly influences the fatigue-based mechanisms that hinder motor performance. Specifically, the greater recovery of maximal strength with longer recovery intervals can partially be explained by greater rates of recovery in supraspinal excitability, corticospinal inhibition, and voluntary activation (1). Therefore, the data produced from fatigue protocols with relatively long recovery intervals may more faithfully bridge the gap from the laboratory to the field.…”