Effect of muscle length in a handgrip task on corticomotor excitability of extrinsic and intrinsic hand muscles under resting and submaximal contraction conditions

Victor Hugo Moraes, Claudia D. Vargas, Bia L. Ramalho, Renan H. Matsuda, Victor H. Souza, Luis Aureliano Imbiriba, Marco Antonio C. Garcia*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The neurophysiological mechanisms underlying muscle force control for different wrist postures still need to be better understood. To further elucidate these mechanisms, the present study aimed to investigate the effects of wrist posture on the corticospinal excitability by transcranial magnetic stimulation (TMS) of extrinsic (flexor [FCR] and extensor carpi radialis [ECR]) and intrinsic (flexor pollicis brevis (FPB)) muscles at rest and during a submaximal handgrip strength task. Fourteen subjects (24.06 ± 2.28 years) without neurological or motor disorders were included. We assessed how the wrist posture (neutral: 0°; flexed: +45°; extended: −45°) affects maximal handgrip strength (HGSmax) and the motor evoked potentials (MEP) amplitudes during rest and active muscle contractions. HGSmax was higher at 0° (133%) than at −45° (93.6%; p < 0.001) and +45° (73.9%; p < 0.001). MEP amplitudes were higher for the FCR at +45° (83.6%) than at −45° (45.2%; p = 0.019) and at +45° (156%; p < 0.001) and 0° (146%; p = 0.014) than at −45° (106%) at rest and active condition, respectively. Regarding the ECR, the MEP amplitudes were higher at −45° (113%) than at +45° (60.8%; p < 0.001) and 0° (72.6%; p = 0.008), and at −45° (138%) than +45° (96.7%; p = 0.007) also at rest and active conditions, respectively. In contrast, the FPB did not reveal any difference among wrist postures and conditions. Although extrinsic and intrinsic hand muscles exhibit overlapping cortical representations and partially share the same innervation, they can be modulated differently depending on the biomechanical constraints.

Original languageEnglish
Pages (from-to)2524-2533
Number of pages10
JournalSCANDINAVIAN JOURNAL OF MEDICINE AND SCIENCE IN SPORTS
Volume33
Issue number12
Early online date29 Aug 2023
DOIs
Publication statusPublished - Dec 2023
MoE publication typeA1 Journal article-refereed

Keywords

  • handgrip strength
  • motor evoked potentials
  • transcranial magnetic stimulation
  • wrist joint

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