Effects of dehydration, hyperthermia, cognition aspects and fatigue balance on sport performance
This dissertation presents two studies. The first is a systematic review, aimed at investigating the effects of hypohydration and fluid balance on athlete’s cognitive function. PubMed, Sports Discuss, and Ebsco databases from 2005 to 2020 were searched for studies reporting on hypohydration, fluid balance, and heat on cognitive performance in sport. Search phrases included hydration, dehydration, fluid balance, mood, cognition, vigilance, decision-making, and brain. Participants in the studies received either fluid or none during exercise. Twenty-four trials (n=493 participants) from 24 articles met the inclusion criteria. Significant hypohydration, >2% body mass loss was reported consistently in 16 publications. Five articles reported that hypohydration was associated with heat stress and that limited fluid intake (3-5% body mass loss) impaired cognitive performance. Mood disturbance, fatigue, and ratings of perceived exertion constantly complemented hypohydration impairment on cognition. The second study examined the effects of exercise heat-stress, hyperthermia, dehydration, and fatigue on cognitive performances in semi-professional athletes. Eighteen healthy, active male athletes from individual and team sports who met the following criteria were chosen to participate in the study: age (25 ± 5) years, weight (69.3±6.6) kg; height (172.5±7.8) cm, BMI (23.2±0.9) kg/m² and body fat % (9.2±1.8). Participants completed a cognitive and mood test battery prior, immediately after, and post 120 minutes of treadmill exercise. A soccer-specific intermittent treadmill exercise protocol was completed in four experimental trials in temperate (normothermic) and hot (hyperthermic) conditions. Participants were hydrated and dehydrated in both conditions. Trial conditions were normothermic 16.4±0.02°C and 52±1% relative humidity, while hyperthermic 33.9±0.3°C and 61±1% relative humidity. Response times for the Stroop effect and Visual search tasks were quicker (584 to 690ms, p=0.001; 1978 to 2213 ms, p=0.003) in the heat. Cognitive tasks showed that reaction time, visual process, motor speed, and mood were similar in normothermic (p=0.001). ii Accuracy improved in hydrated hyperthermic by 1.2% (p=0.002) in Visual search. Total Mood Disturbance was significant in heat (p<0.001). Hydration status had no main effect in all cognition performance markers except for mood. Exercise-heat stress, hyperthermia, dehydration, and hypohydration impaired cognitive performance and mood at higher levels of 3-5% body mass loss. The response times and accuracy improved following the cognitive testing in semi-professional athletes exercising in relatively humid, hot conditions. Athletic and cognitive performances were relatively affected by hypohydration, which can indicate an athlete’s hydration status needs to be closely monitored during exercise. The findings of this study obtained from Eswatini individual and team sport athletes support that maintaining normal hydration has low physiological strain on athletic and cognitive performance
Cognitive function, fluid replenishment, hypohydration, intermittent exercise
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