Central nervous adaptations following 1 week of wrist and hand immobilization

TY - JOUR

T1 - Central nervous adaptations following 1 week of wrist and hand immobilization

AU - Lundbye-Jensen, Jesper

AU - Nielsen, Jens Bo

N1 - CURIS 2008 5200 050

PY - 2008

Y1 - 2008

N2 - Plastic neural changes have been documented in relation to different types of physical activity but little is known about central nervous system plasticity accompanying reduced physical activity and immobilization. In the present study we investigated whether plastic neural changes occur in relation to one week of immobilization of the non-dominant wrist and hand and a corresponding period of recovery in 10 able-bodied volunteers. Following immobilization maximal voluntary contraction torque (MVC) decreased and the variability of submaximal static contractions increased significantly without evidence of changes in muscle contractile properties. H-reflex amplitudes and H-slope/M-slope ratios increased significantly in flexor carpi radialis (FCR) and abductor pollicis brevis (APB) at rest and during contraction without changes in corticospinal excitability estimated from motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). Corticomuscular coherence measures were derived from EEG and EMG obtained during static contractions. Following immobilization corticomuscular coherence in the 15-35 Hz range associated with maximum negative cumulant values at lags corresponding to MEP latencies decreased. One week after cast removal all measurements returned to pre immobilization levels. The increased H-reflex amplitudes without changes in MEPs may suggest that presynaptic inhibition or post activation depression of Ia afferents is reduced following immobilization. Reduced corticomuscular coherence may be caused by changes in afferent input at spinal and cortical levels or by changes in the descending drive from motor cortex. Further studies are needed to elucidate the mechanisms underlying the observed increased spinal excitability and reduced coupling between motor cortex and spinal motoneuronal activity following immobilization. Key words: Plasticity, Immobilization, Motor Control.

AB - Plastic neural changes have been documented in relation to different types of physical activity but little is known about central nervous system plasticity accompanying reduced physical activity and immobilization. In the present study we investigated whether plastic neural changes occur in relation to one week of immobilization of the non-dominant wrist and hand and a corresponding period of recovery in 10 able-bodied volunteers. Following immobilization maximal voluntary contraction torque (MVC) decreased and the variability of submaximal static contractions increased significantly without evidence of changes in muscle contractile properties. H-reflex amplitudes and H-slope/M-slope ratios increased significantly in flexor carpi radialis (FCR) and abductor pollicis brevis (APB) at rest and during contraction without changes in corticospinal excitability estimated from motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). Corticomuscular coherence measures were derived from EEG and EMG obtained during static contractions. Following immobilization corticomuscular coherence in the 15-35 Hz range associated with maximum negative cumulant values at lags corresponding to MEP latencies decreased. One week after cast removal all measurements returned to pre immobilization levels. The increased H-reflex amplitudes without changes in MEPs may suggest that presynaptic inhibition or post activation depression of Ia afferents is reduced following immobilization. Reduced corticomuscular coherence may be caused by changes in afferent input at spinal and cortical levels or by changes in the descending drive from motor cortex. Further studies are needed to elucidate the mechanisms underlying the observed increased spinal excitability and reduced coupling between motor cortex and spinal motoneuronal activity following immobilization. Key words: Plasticity, Immobilization, Motor Control.

U2 - 10.1152/japplphysiol.00687.2007

DO - 10.1152/japplphysiol.00687.2007

M3 - Journal article

C2 - 18450985

SN - 8750-7587

VL - 105

SP - 139

EP - 151

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

IS - 1

ER -