Abstract:
Introduction: Lowered substrate availability and exercise-induced fatigue are known to perturb metabolic homeostasis and result in decrements in physical performance. Despite a wealth of evidence in this area of physiology little is currently known about the effects of energy depletion and fatigue upon visual performance. Additionally no research to date has investigated whether the ingestion of carbohydrate can attenuate decrements in visual function. Purpose: This study examined the effects of exercise-induced fatigue and energy depletion upon visual performance, specifically saccadic eye movement, motion coherence, binocularity, depth perception and near and distant visual acuity. Method: In a double-blind, randomised, cross-over design, nine males (mean age: 30.5 yr and O2max 60.95 ml·kg-1) consumed either placebo (PLA) or carbohydrate (CHO) solutions every 15 min during a 3 h cycling exercise protocol. Visual measures of performance were assessed pre and post the completion of the exercise protocol. Heart rate and perceived exertion (effort sense) were recorded throughout the duration of the protocol and venous blood samples were collected at routine intervals. Results: A significant improvement in the performance of congruent saccades was detected during the CHO trial and decrements in saccade velocity and accuracy were observed in both trials. There was also a significant congruency effect observed in all saccadic eye movement tests performed. Conclusion: The main findings of this study were that energy depletion and fatigue influence ocular motor control after 180 min of strenuous exercise. Decrements in performance did not appear to relate to either delays in cognitive processing or extraocular muscular fatigue. The findings from this study support the possibility of the existence of a supraspinal fatigue association with decrements in visual performance.