Effects of eccentric versus concentric contractions of the biceps brachii on intracortical inhibition and facilitation

Abstract

Differences in the neural mechanisms underpinning eccentric (ECC) and concentric (CON) contractions exist; however, the acute effects of fatiguing muscle contractions on intracortical and corticospinal excitability are not well understood. Therefore, we compared maximal ECC and CON contractions of the right biceps brachii (BB) muscle for changes in corticospinal excitability, short‐ (SICI) and long‐interval intracortical inhibition (LICI) and intracortical facilitation (ICF) up to 1 hour post‐exercise. Fourteen right‐handed adults (11 M/3F; 26.8 ± 2.9 year) undertook a single session of 3 sets of 10 maximal ECC or CON contractions (180‐second rest between sets) on an isokinetic dynamometer (40°/s) separated by 1 week, in a randomized crossover study. Maximum voluntary isometric contraction torque (MVIC), maximal muscle compound waves (MMAX), and motor‐evoked potentials elicited through transcranial magnetic stimulation (TMS) were recorded via surface electromyography from the right BB. MVIC decreased (P < 0.001) immediately after ECC and CON contractions similarly, but the decrease was sustained at 1 hour post‐ECC contractions only. MMAX was reduced immediately (P = 0.014) and 1 hour post‐exercise (P = 0.019) only for ECC contractions. SICI and ICF increased immediately after ECC and CON contractions (P < 0.001), but LICI increased only after ECC contractions (P < 0.001), and these increases remained at 1 hour post‐ECC contractions only. These findings suggest that ECC contractions induced a longer‐lasting neuromodulatory effect on intracortical inhibition and facilitation, which could indicate a central compensatory response to peripheral fatigue.

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

“…Interestingly, studies investigating the effect of fatigue-related group III and IV afferent feedback on neurophysiological responses showed an increase in long-interval intracortical inhibition following cycling exercise (90,91), rather than a decrease that was observed in the present study and others (48,78) following lengthening contractions. However, cycling is an activity that predominantly consists of shortening, rather than lengthening contractions.…”

“…However, cycling is an activity that predominantly consists of shortening, rather than lengthening contractions. Thus, it is possible that modulation of inhibitory mechanisms is contraction-mode specific, as suggested by a recent study (48). Alternatively, afferent feedback might mediate specific inhibitory networks differently.…”

Locomotor Activities as a Way of Inducing Neuroplasticity: Insights and Perspectives on Conventional and Eccentric Exercise Approaches

“…The mode of muscle contraction did not affect corticospinal excitability changes evaluated after elbow flexions (Latella et al, 2018;Löscher and Nordlund, 2002) or knee extensions (Clos et al, 2020;Garnier et al, 2018). Some authors nevertheless reported reductions in short-interval intracortical inhibition (lasting two hours, Pitman and Semmler, 2012), long-interval intracortical inhibition and silent period duration (Škarabot et al, 2019a), and increases in intracortical facilitation (lasting one hour Latella et al, 2018). These changes were suggested to be the consequence of an impaired motor control resulting from muscle damage (Pitman and Semmler, 2012;Škarabot et al, 2019a).…”

“…Greater spinal inhibition, mediated by supraspinal mechanisms, was thus proposed to regulate the motor command, again in order to preserve the integrity of the muscletendon complex (Sekiguchi et al, 2003(Sekiguchi et al, , 2001. The mode of muscle contraction did not affect corticospinal excitability changes evaluated after elbow flexions (Latella et al, 2018;Löscher and Nordlund, 2002) or knee extensions (Clos et al, 2020;Garnier et al, 2018). Some authors nevertheless reported reductions in short-interval intracortical inhibition (lasting two hours, Pitman and Semmler, 2012), long-interval intracortical inhibition and silent period duration (Škarabot et al, 2019a), and increases in intracortical facilitation (lasting one hour Latella et al, 2018).…”

Locomotor activities as a way of inducing neuroplasticity: insights from conventional approaches and perspectives on eccentric exercises

“…Some authors measured reductions in cortical inhibition and increase in cortical facilitation immediately and until two hours after the completion of single-joint eccentric contractions [26,78], and suggested it to be the consequence of an impaired motor control resulting from muscle damage [26,81]. The long-lasting influence of eccentric contractions on cortical processes might also result from the greater motor control required to perform these tasks [80].…”