Does rest interval between unilateral exercise protocols influences on contralateral neuromuscular responses in untrained individuals?

INTRODUCTION: Effects on strength performance and muscle activation in the contralateral limb have been observed after training with the ipsilateral limb (IL). Cross fatigue effects in the contralateral limb (CL) can occur at intervals of up to 48 h after a training session performed with the ipsilateral limb. The objective of this study was to verify the effect of a training session in the ipsilateral limb, on the strength and activation of the muscles in the contralateral limb also submitted to the training protocol. METHODS: 10 untrained men (mean ± SD: age = 23.7 ± 4.9 years) performed unilateral knee extension with both limbs in equated protocols, in two conditions with different intervals between limbs - 20 min and 24 h. RESULTS: There were no differences in the comparison of the force produced between the pre x post interventions with the CL limb, as well as in the activation of the quadriceps during its performance. These results were similar for the two different intervals between the protocols. CONCLUSION: It was concluded that when the CL member performs the protocol after the IL, the responses in the CL depend mainly on the requirement imposed on the protocol performed by this member, without influence of the training protocol performed previously with the IL member.

Mental practice is associated with learning the relative timing dimension of a task.

Learning about the relative timing dimension of a motor skill is enhanced by factors that promote higher response stability between trials. Conversely, learning the absolute timing dimension is favored by lower trial-to-trial stability. The mental practice may increase response stability during acquisition since there is a low possibility of adjustments made between trials. Thus, this study aimed to test the hypothesis that some factors that increase response stability during the acquisition phase contribute to an enhanced relative timing dimension learning. Our hypothesis is that mental practice shows less relative timing error than the absence of practice. A sequential key-pressing task was practiced with two goals: learn (1) relative timing dimension and (2) absolute timing dimension. Participants were assigned to one of three groups: Physical, Mental, or No practice. The Physical group showed greater learning of both dimensions than the other two groups. The Mental group showed greater learning of relative timing dimension than the No practice group. The results suggest that mental practice produces increased stability, which in turn promotes learning of the relative timing dimension.