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.
Be between the ages of 18 - 30
Healthy (no medical conditions)
If female, must be taking the same monophasic oral contraceptive for the past 6 months
Have a body mass index between 18.5 - 30 kg/m2
If transcranial magnetic stimulation (TMS) is not deemed appropriate depending on your responses to the TMS-specific questionnaire
Being ambidextrous
Although rare, you will be excluded if discernable muscle activation responses are not possible via TMS
Crossover
Imagined muscle contractions
BehavioralThe intervention involved imagining, with no physical movement, of muscle contractions.
Change in rate of torque development as measured by newton-meters per second
A measure of the capacity to increase muscle torque rapidly as determined by the slope of the torque-time curve
Change in nervous system excitability as measured by electromyographic waveform aplitude following motor cortex stimulation
A measure of excitability for the corticospinal tract
Change in isometric bicep strength as measured by newton-meters of torque
Isometric strength of a muscle
Change in agonist muscle activation as measured by electromyography amplitude
A measure of the capacity at which the muscle is activated by the nervous system
Change in antagonist co-activation as measured by electromyography amplitude
A measure of the capacity at which the antagonist muscle is activated by the nervous system
Change in rate of agonist muscle activation as measured by electromyography amplitude
A measure of how quickly the nervous system activates the muscle
Self-reported ability to imagine movements as measured by Movement Imagery Questionnaire-Revised as measured on a scale from 8 to 56
Survey that estimates one's capacity to imagine movement. A higher score indicates better imagination.
Level of vividness for imagining the imagined contractions as measured by 7-point likert scale as measured from 1 to 7
A 7-point likert scale is used to to determine how vivid one's imagination was for the conditions. A higher score indicates greater difficulty imagining the movement.
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