The effects of fatiguing exercise and load carriage on the perception and initiation of movement

Abstract

Perceptual-motor coordination relies on the accurate coupling of the perceptual and movement systems. However, individuals must also be able to recalibrate to perturbations to perceptual and movement capabilities. We examined the effects of fatigue and load carriage on perceptual-motor coordination for a maximal leaping task. 23 participants completed an incremental fatigue protocol (light to fatiguing intensity stages) on two separate occasions (loaded/ unloaded). At baseline and the end of every stage of the protocol, participants made perceptual judgments for the affordance of leaping. The accuracy of responses and reaction times were calculated and mean differences were assessed across exercise intensity and load carriage conditions. No interaction of exercise intensity and load carriage was detected, or main effect of load carriage. A main, quadratic effect of exercise intensity was detected on reaction times, with times decreasing through the moderate stage and increasing through post-fatigue. No effect of exercise/fatigue was detected on perceptual accuracy. The results indicate that exercise at high intensities through fatigue has a significant effect on perceptual-motor calibration. Contrastingly, in response to an action-scaled task, individuals can adequately recalibrate to increased load carriage.

Sex‐ and age‐related differences in kinetics and tibial accelerations during military‐relevant movement tasks in U.S. Army trainees

“…The pack weight and ruck marching speed were selected based on average prescribed weights/speeds for ruck marching at the beginning of BCT. This was determined primarily through discussions with BCT Unit Commanders, but also through experience with conducting load carriage studies (Johnson, Eagle, et al., 2020).…”

Physiological impact of load carriage exercise: Current understanding and future research directions

“…Current literature also recommends that to delay time to fatigue during sub‐maximal exercise (prolonged marching activity), load and speed should be carefully managed to maintain an exercise intensity ~45% V̇ O 2 max (Johnson et al, 2021 ). Furthermore, a study deriving the load–speed index (LSI), corroborated this finding, identifying 47% V̇ O 2 max as a threshold above which intensity increases at a greater rate with increases in two critical factors of load carriage; i.e., load and speed (Boffey et al, 2019 ).…”