Fatiguing unilateral handgrip influences force during force-matching task with lower limb

This study aimed to test the hypotheses that fatiguing unilateral handgrip contraction exhibits different changes in corticomotor excitability, which is evaluated by motor-evoked potentials (MEPs), in the lower limbs ipsilateral and contralateral to the fatigued hand, and that the changes in corticomotor excitability estimated by MEPs in the non-fatigued lower limbs affect the force exerted based on the sense of effort. Ten healthy males completed fatiguing unilateral handgrip contraction and force-matching tasks by static dorsiflexion before, immediately after, and 10 min after handgrip contraction. MEPs in the tibialis anterior (TA) were also measured before, immediately after, and 10 min after handgrip contraction. Fatiguing handgrip contractions resulted in asymmetrical MEPs in the TA muscles. Specifically, MEPs in the contralateral TA muscle were significantly increased (158 ± 60 %) and MEPs in the contralateral TA muscle were greater after the handgrip contraction than the ipsilateral MEPs (111 ± 30 %). Moreover, the torque exerted during the force-matching task significantly increased only in the contralateral ankle after the fatiguing handgrip contraction. Fatiguing unilateral handgrip contraction results in asymmetric changes in corticomotor excitability in the TA muscle, and the force exerted during the force-matching task based on the sense of effort becomes higher in the TA muscle with greater corticomotor excitability than that before fatiguing unilateral handgrip contraction.