Title

Neuromuscular responses to an instantaneous force change in exhaustive bouts of exercise

Presentation Type

Poster

Abstract

Purpose: This study examined the mechanisms used by the muscular and nervous systems to maintain force production in exhaustive exercise trials.

Methods: The subjects reported to the laboratory a minimum of 8 times. During each visit, subjects typically completed 5 high-speed treadmill sprints to failure. We measured descending motor drive and neuromuscular activity via bipolar surface EMG and simultaneous gait kinetics from a custom force instrumented treadmill.

Originality: Human runners, change speed by altering the forces applied against the ground during foot-ground contact. Previously, our laboratory has identified the force thresholds necessary to trigger the onset of compensatory neuromuscular activity, which is used to maintain force production during efforts inducing muscle fatigue and ultimately eliciting task failure. At lower levels of force production and effort, this compensatory behavior is absent and EMG measures are essentially steady throughout the activity. We used a novel experimental protocol involving a mid-trial 15% speed change, which was either positive or negative, blinded to both the research team and the subject, and randomly administered to evaluate whether the accumulation and development of fatigue occurred in response to the level of muscle force applied. We therefore specifically expected to observe either increments or decrements in the rate of neuromuscular compensation based on the direction of the speed change administered.

Significance: This study informs the mechanisms used by the neuromuscular systems to communicate the development and time course of force impairment that occurs during muscle fatigue.

Category

Physical Sciences

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Apr 15th, 11:00 AM Apr 15th, 12:00 PM

Neuromuscular responses to an instantaneous force change in exhaustive bouts of exercise

Purpose: This study examined the mechanisms used by the muscular and nervous systems to maintain force production in exhaustive exercise trials.

Methods: The subjects reported to the laboratory a minimum of 8 times. During each visit, subjects typically completed 5 high-speed treadmill sprints to failure. We measured descending motor drive and neuromuscular activity via bipolar surface EMG and simultaneous gait kinetics from a custom force instrumented treadmill.

Originality: Human runners, change speed by altering the forces applied against the ground during foot-ground contact. Previously, our laboratory has identified the force thresholds necessary to trigger the onset of compensatory neuromuscular activity, which is used to maintain force production during efforts inducing muscle fatigue and ultimately eliciting task failure. At lower levels of force production and effort, this compensatory behavior is absent and EMG measures are essentially steady throughout the activity. We used a novel experimental protocol involving a mid-trial 15% speed change, which was either positive or negative, blinded to both the research team and the subject, and randomly administered to evaluate whether the accumulation and development of fatigue occurred in response to the level of muscle force applied. We therefore specifically expected to observe either increments or decrements in the rate of neuromuscular compensation based on the direction of the speed change administered.

Significance: This study informs the mechanisms used by the neuromuscular systems to communicate the development and time course of force impairment that occurs during muscle fatigue.