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

Author(s)

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

• Document type: Journal article
• Source: SCANDINAVIAN JOURNAL OF MEDICINE & SCIENCE IN SPORTS; v. N/A, p. 10-pg., 2023-08-29.

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 degrees; flexed: +45 degrees; extended: -45 degrees) affects maximal handgrip strength (HGS(max)) and the motor evoked potentials (MEP) amplitudes during rest and active muscle contractions. HGS(max) was higher at 0 degrees (133%) than at -45 degrees (93.6%; p < 0.001) and +45 degrees (73.9%; p < 0.001). MEP amplitudes were higher for the FCR at +45 degrees (83.6%) than at -45 degrees (45.2%; p = 0.019) and at +45 degrees (156%; p < 0.001) and 0 degrees (146%; p = 0.014) than at -45 degrees (106%) at rest and active condition, respectively. Regarding the ECR, the MEP amplitudes were higher at -45 degrees (113%) than at +45 degrees (60.8%; p < 0.001) and 0 degrees (72.6%; p = 0.008), and at -45 degrees (138%) than +45 degrees (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. (AU)

• FAPESP's process: 22/00582-9 - Retrieving context tree models driven by structured TMS pulse sequences applied in the primary motor cortex.
• Grantee: Bia Ramalho dos Santos Lima
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/07699-0 - Research, Innovation and Dissemination Center for Neuromathematics - NeuroMat
• Grantee: Oswaldo Baffa Filho
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 22/14526-3 - Can a context tree model predict the primary motor cortex excitability? An electromyography and electroencephalography robotized navigated transcranial magnetic stimulation study.
• Grantee: Renan Hiroshi Matsuda
• Support Opportunities: Scholarships in Brazil - Post-Doctoral