TY - JOUR

T1 - Plasticity in central neural drive with short-term disuse and recovery - effects on muscle strength and influence of aging

AU - Hvid, Lars G.

AU - Aagaard, Per

AU - Ørtenblad, Niels

AU - Kjaer, Michael

AU - Suetta, Charlotte

PY - 2018

Y1 - 2018

N2 - While short-term disuse negatively affects mechanical muscle function (e.g. isometric muscle strength) little is known of the relative contribution of adaptions in central neural drive and peripheral muscle contractility. The present study investigated the relative contribution of adaptations in central neural drive and peripheral muscle contractility on changes in isometric muscle strength following short-term unilateral disuse (4 days, knee brace) and subsequent active recovery (7 days, one session of resistance training) in young (n = 11, 24 yrs) and old healthy men (n = 11, 67 yrs). Maximal isometric knee extensor strength (MVC) (isokinetic dynamometer), voluntary muscle activation (superimposed twitch technique), and electrically evoked muscle twitch force (single and doublet twitch stimulation) were assessed prior to and after disuse, and after recovery. Following disuse, relative decreases in MVC did not differ statistically between old (16.4 ± 3.7%, p < 0.05) and young (−9.7 ± 2.9%, p < 0.05) (mean ± SE), whereas voluntary muscle activation decreased more (p < 0.05) in old (−8.4 ± 3.5%, p < 0.05) compared to young (−1.1 ± 1.0%, ns) as did peak single (−25.8 ± 6.6%, p < 0.05 vs −7.6 ± 3.3%, p < 0.05) and doublet twitch force (−23.2 ± 5.5%, p < 0.05 vs −2.0 ± 2.6%, ns). All parameters were restored in young following 7 days recovery, whereas MVC and peak twitch force remained suppressed in old. Regression analysis revealed that disuse-induced changes in MVC relied more on changes in single twitch force in young (p < 0.05) and more on changes in voluntary muscle activation in old (p < 0.05), whereas recovery-induced changes in MVC mainly were explained by gains in voluntary muscle activation in both young and old. Altogether, the present data demonstrate that plasticity in voluntary muscle activation (~central neural drive) is a dominant mechanism affecting short-term disuse- and recovery-induced changes in muscle strength in older adults.

AB - While short-term disuse negatively affects mechanical muscle function (e.g. isometric muscle strength) little is known of the relative contribution of adaptions in central neural drive and peripheral muscle contractility. The present study investigated the relative contribution of adaptations in central neural drive and peripheral muscle contractility on changes in isometric muscle strength following short-term unilateral disuse (4 days, knee brace) and subsequent active recovery (7 days, one session of resistance training) in young (n = 11, 24 yrs) and old healthy men (n = 11, 67 yrs). Maximal isometric knee extensor strength (MVC) (isokinetic dynamometer), voluntary muscle activation (superimposed twitch technique), and electrically evoked muscle twitch force (single and doublet twitch stimulation) were assessed prior to and after disuse, and after recovery. Following disuse, relative decreases in MVC did not differ statistically between old (16.4 ± 3.7%, p < 0.05) and young (−9.7 ± 2.9%, p < 0.05) (mean ± SE), whereas voluntary muscle activation decreased more (p < 0.05) in old (−8.4 ± 3.5%, p < 0.05) compared to young (−1.1 ± 1.0%, ns) as did peak single (−25.8 ± 6.6%, p < 0.05 vs −7.6 ± 3.3%, p < 0.05) and doublet twitch force (−23.2 ± 5.5%, p < 0.05 vs −2.0 ± 2.6%, ns). All parameters were restored in young following 7 days recovery, whereas MVC and peak twitch force remained suppressed in old. Regression analysis revealed that disuse-induced changes in MVC relied more on changes in single twitch force in young (p < 0.05) and more on changes in voluntary muscle activation in old (p < 0.05), whereas recovery-induced changes in MVC mainly were explained by gains in voluntary muscle activation in both young and old. Altogether, the present data demonstrate that plasticity in voluntary muscle activation (~central neural drive) is a dominant mechanism affecting short-term disuse- and recovery-induced changes in muscle strength in older adults.

KW - Central neural drive

KW - Disuse

KW - Mechanical muscle function

KW - Muscle contractile properties

KW - Voluntary muscle activation

U2 - 10.1016/j.exger.2018.02.019

DO - 10.1016/j.exger.2018.02.019

M3 - Journal article

C2 - 29476804

AN - SCOPUS:85043470201

VL - 106

SP - 145

EP - 153

JO - Experimental Gerontology

JF - Experimental Gerontology

SN - 0531-5565

ER -