EFFECTS OF EXERCISE ON ASPECTS OF VISUAL FUNCTION

Strenuous exercise has been reported to affect various aspects of visu al and ocular function. In the first of two experiments, the effects o f cycling, jogging and stair running on a range of visual functions we re examined. None of these forms of exercise was found to have any sig nificant effect on visual acuity, refractive error, dark focus, amplit ude of accommodation or pupil size. Contrast sensitivity (CS), measure d by an ascending method of limits (AML), was found to improve signifi cantly after cycling and jogging but not after stair running. To inves tigate if the apparent improvement in CS was related to a change in 's ensitivity' or a change in decision criteria, CS was re-measured befor e and after cycling using both the AML and a 'criterion-free' method o f constant stimuli (MOCS) procedure. Results obtained using the AML, c onfirmed the findings of the first experiment. However, results obtain ed using the MOCS procedure showed no significant change with exercise . This suggests that the improvement in CS found using the AML was due to a shift in subjects' decision criteria rather than a physiological change in 'sensitivity'. It is argued that this change in decision cr iteria may be related to the positive mood changes which have been fou nd to occur after exercise. This study demonstrates the importance of differentiating between changes in 'sensitivity' and changes in decisi on criteria especially where mood or motivation (and hence decision cr iteria) may be confounded with the independent variable. This is parti cularly important when evaluating the effects of exercise on visual fu nction or evaluating the efficacy of vision training.