Document Type
Article
Language
eng
Publication Date
9-2016
Publisher
Springer
Source Publication
Experimental Brain Research
Source ISSN
1432-1106
Original Item ID
DOI: 10.1007/s00221-016-4658-9
Abstract
This study determined whether short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) change during a sustained submaximal isometric contraction. On 2 days, 12 participants (6 men, 6 women) performed brief (7-s) elbow flexor contractions before and after a 10-min fatiguing contraction; all contractions were performed at the level of integrated electromyographic activity (EMG) which produced 25 % maximal unfatigued torque. During the brief 7-s and 10-min submaximal contractions, single (test) and paired (conditioning–test) transcranial magnetic stimuli were applied over the motor cortex (5 s apart) to elicit motor-evoked potentials (MEPs) in biceps brachii. SICI and ICF were elicited on separate days, with a conditioning–test interstimulus interval of 2.5 and 15 ms, respectively. On both days, integrated EMG remained constant while torque fell during the sustained contraction by ~51.5 % from control contractions, perceived effort increased threefold, and MVC declined by 21–22 %. For SICI, the conditioned MEP during control contractions (74.1 ± 2.5 % of unconditioned MEP) increased (less inhibition) during the sustained contraction (last 2.5 min: 86.0 ± 5.1 %; P < 0.05). It remained elevated in recovery contractions at 2 min (82.0 ± 3.8 %; P < 0.05) and returned toward control at 7-min recovery (76.3 ± 3.2 %). ICF during control contractions (conditioned MEP 129.7 ± 4.8 % of unconditioned MEP) decreased (less facilitation) during the sustained contraction (last 2.5 min: 107.6 ± 6.8 %; P < 0.05) and recovered to 122.8 ± 4.3 % during contractions after 2 min of recovery. Both intracortical inhibitory and facilitatory circuits become less excitable with fatigue when assessed during voluntary activity, but their different time courses of recovery suggest different mechanisms for the fatigue-related changes of SICI and ICF.
Recommended Citation
Hunter, Sandra K.; McNeil, Chris J.; Butler, Jane E.; Gandevia, Simon C.; and Taylor, Janet L., "Short-Interval Cortical Inhibition and Intracortical Facilitation during Submaximal Voluntary Contractions Changes with Fatigue" (2016). Exercise Science Faculty Research and Publications. 99.
https://epublications.marquette.edu/exsci_fac/99
Comments
Accepted version. Experimental Brain Research, Vol. 234, No. 9 (September 2016): 2541-2551. Final publication available at Springer via DOI. © 2016 Springer. Used with permission.
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