DOES PHOSPHOCREATINE PLAY A ROLE IN THE MENTAL FATIGUE-ASSOCIATED DECREASE IN SPORT-SPECIFIC PSYCHOMOTOR PERFORMANCE?

INTRODUCTION: Sport performance is determined by a combination of physiological and cognitive capacity. Recently the importance of the brain/cognitive capacity in sport performance has been further substantiated by research demonstrating the negative effect of mental fatigue (MF) on sport-specific psychomotor skills [1]. Creatine supplementation improves strength, but can also improve cognitive functioning [2]. To further explore creatine’s role as a cognitive enhancer and unravel the mechanisms behind the MF-associated decrease in sport performance, the aim was to evaluate the role of phosphocreatine in the MF-associated impairments in cognitive performance and sport-specific psychomotor skills. METHODS: In 23°C and 35% relative humidity, 14 healthy subjects (4F 10M; mean ± SD; age:24 ± 3 y; mass:74 ± 13 kg; height:179 ± 9 cm) performed - counterbalanced, crossover and double blinded - a 7-min sport-specific visuomotor task before and after a 90-min mentally fatiguing task (i.e. Stroop task) in two different conditions: after a 7-day creatine supplementation (CR; experimental; 20 g/day) and after a 7-day calcium lactate supplementation (PLAC; placebo), separated by a 5-week washout. In both conditions, a dynamic handgrip strength endurance task (12 maximal reps) and a 3-min Flanker task was performed before and after the mentally fatiguing task. Physiological and perceptual responses were measured throughout the protocol. Normality was checked, repeated measures ANOVAs were employed to observe interaction and/or main effects of condition and time. Follow up tests were performed where necessary (p<0.05). RESULTS: Dynamic handgrip strength endurance was higher in CR compared to PLAC (last 3 reps/first 3 reps * 100: CR=84 ± 2%; PLAC=79.5 ± 1.9%; p=0.022, ηp2=0.344), indicating the creatine supplementation protocol was successful. Elevated self-reported MF (+45/100; p<0.001, ηp2=0.713) and decreased Flanker accuracy (-5.3%; p=0.012, ηp2=0.419) after the mentally fatiguing task in both CR and PLAC supported MF was present in both conditions. MF impaired visuomotor response time by 4.3% (p=0.022, ηp2=0.343) in both conditions. Overall accuracy on the mentally fatiguing task was higher in CR compared to PLAC (p=0.026, ηp2=0.348). Motivation and vigour (p≤0.027) were higher in PLAC compared to CR, while other perceptual variables, heart rate and glucose did not differ between conditions. CONCLUSION: Creatine supplementation improved physical (strength endurance) and prolonged cognitive (Stroop accuracy) performance, yet it did not affect short sport-specific psychomotor or Flanker performance. From a practical point of view these results warrants further investigation in the potential role of creatine in countering the MF-associated decrements in prolonged (>7 min; e.g. 90-min soccer game) sport performance. From a mechanistic point of view the results suggest a possible role of brain-phosphocreatine in MF. References: 1. Russel et al.J Sci Med Sport,2018 2. McMorris et al.Psychopharmacology,2006