Abstract
Purpose: :
Physical fatigue and hypoglycemia can seriously impair performance of motor tasks. It is currently unclear, however, whether the human visual system is also susceptible to this type of functional impairment. The aim of this study was to assess the extent to which the neural control of eye movements and cortical processing of visual information are susceptible to exercise induced central fatigue and hypoglycemia.
Methods: :
Within a double-blind, randomized, cross-over design, 9 male cyclists (mean age 30.5 years) consumed either placebo (fatigue and hypoglycemia condition) or carbohydrate (fatigue alone condition) solutions every 15 min during a 180 min cycling exercise protocol. The exercise workload was equivalent to 60% of each participant’s maximum aerobic capacity. Visual acuity, binocular function, global motion perception and saccadic eye moments, assessed within the context of an established social attention eye movement paradigm, were measured before and after the exercise protocol. Eye movements were recorded using an infra-red eye-tracker. Heart rate and perceived exertion were recorded throughout the duration of the protocol and venous blood samples were collected at routine intervals for assessment of plasma glucose concentration.
Results: :
Fatigue alone or fatigue and hypoglycemia did not reduce visual acuity, binocular visual function, global motion perception or the effects of social attention on the latency of eye movements. There was, however, a significant reduction in the velocity (F[1,8] = 18.4, p = 0.003) and accuracy (F[1,8] = 34.7, p < 0.001) of saccades for both the fatigue alone and fatigue and hypoglycemia conditions.
Conclusions: :
Neural processing of visual information is robust to exercise induced fatigue and hypoglycemia however ocular motor control is susceptible to the effects of strenuous exercise. This suggests that sensory processing may have priority over ocular-motor control when energy resources are depleted.
Keywords: eye movements: saccades and pursuits • motion-2D • perception