Simultaneous Physical and Mental Effort Alters Visual Function

PURPOSE: Perceptual processing is sensitive to physiological changes. Thus, the homeostatic disturbances during and after exercise may alter the visual function. Here, we investigated the effect of simultaneous physical effort and two levels of cognitive demand on skills related to the visuoperceptual and motor processing. METHODS: Eighteen male regular exercisers performed 60 minutes of simultaneous physical exercise (cycling at 60 +/- 5% of reserve heart rate) and cognitive effort (mental workload). The same protocol was performed with a mental workload and an oddball condition of this task on different days in a counterbalanced manner. We assessed the near point of convergence, near stereoacuity, accommodative facility (Hart Charts), and eye-hand coordination before and after the two dual-tasking sessions. Also, we calculated cognitive-performance scores and subjective measures of mental load. RESULTS: We found that the near point of convergence (break and recovery) is significantly (P <= .05) reduced after physical and mental effort independently of the mental level administered. Only the condition of mental workload with simultaneous constant-intensity cycling promoted a significant impairment in the near stereoacuity and the eye-hand coordination (P = .006 and P = .018, respectively); however, these two parameters did not significantly change under the oddball condition. The accommodative facility showed an improvement in the oddball and mental workload conditions (P < .001 and P = .006, respectively). Confirming a successful experimental manipulation, participants experienced higher mental demand and arousal and achieved lower scores on cognitive performance during the mental workload task (both P < .001). CONCLUSIONS: The visual function is affected by simultaneous physical and mental effort, the manipulation of mental-task complexity being an important modulator of this effect. Both dual tasks, physical with or without mental workload demands, may enhance or impair visual and motor processing depending on the visual parameter tested, and those changes could be related to the activation state of the nervous system.