Influence of Fast and Slow Imagined Muscle Contractions on Muscle Function or Central Nervous System Properties

Overview

The goal of this randomized clinical trial is to learn if imagining fast or slow muscle contractions causes different responses for nervous system excitability and muscle function in young, healthy males and females in. The main questions are: Does imagining fast muscle contractions cause greater nervous system excitability compared to imagining slow muscle contractions? Does imagining fast muscle contractions increase muscle function compared to imagining slow muscle contractions? A control condition (rest) will be compared with two intervention conditions: imagining fast and imagining slow conditions, to determine if the fast and slow increase outcomes more than control and if fast has the greatest response. Participants will: * Attend 4 laboratory visits * Perform 50 imagined contractions fast or slow, but with no physical movement * Physical muscle contractions and non-invasive brain stimulation would be completed before and after each condition.

Participants will complete 4 laboratory visits in a randomized order, including a familiarization session, a control condition, and 2 conditions involving imaginary muscle contractions. During visits involving imaginary muscle contractions, participants will complete 2 sets of 25 repetitions of either fast (i.e., less than 1 second to peak torque increase torque as fast as possible) or slow (i.e., 3 seconds to peak torque) isometric elbow flexions. Before and after each condition, single-pulse transcranial magnetic stimulation will be delivered to the primary motor cortex to measure the amplitude of motor-evoked potentials and the duration of the resulting silent periods in the bicep brachii to quantify changes in corticospinal excitability and inhibition, respectively. Rapid maximal voluntary isometric contractions will be used to measure changes in rate of torque development, peak torque, and rate of muscle activation.