Repeated Sprints in Fasted State Impair Reaction Time Performance

ABSTRACT

Objective: The aim of this study was to assess the effects of 3-day Islamic intermittent fasting (3d-IF) on cognitive performance and serum levels of neurotrophic factors (brain-derived neurotrophic factor [BDNF] and vascular endothelial growth factor [VEGF]) before and after repeated sprints.

Methods: Twenty-one physically active male Muslims (29.8 ± 5.9 years, exercising 4 ± 1.5 times/week) were randomly assigned to one of 2 experimental sessions: the control or nonfasting session (CS) or the fasting session (FS). These 2 sessions occurred 7 days apart in a counterbalanced crossover design. In both conditions, the test was performed at the same time of day, approximately 1 hour before sunset. In the FS, the test occurred on the third day of the 3d-IF and involved the participants' performance of the following: (a) two series of 5 maximal 5-second sprints and (b) 2 cognitive tasks: One Touch Stockings (OTS) and reaction time (simple and complex RTI).

Results: In both conditions, the participants' reaction times during the RTI test were similar at the pre- and mid-exercise points, but postexercise, simple and complex reaction times were higher in FS compared to CS (p = 0.045, effect size [ES] = 0.21 and p = 0.006, ES = 0.41, respectively). However, OTS performance and serum levels of neurotrophic factors were not influenced by the 3d-IF.

Conclusion: Simple and complex reaction times during the RTI test were negatively affected by the 3d-IF after 2 bouts of intensive repeated sprints.

KEYWORDS:

• Dietary restriction
• anaerobic exercise
• cognitive task
• memory
• brain

Acknowledgments

We gratefully acknowledge the cooperation and participation of all of our subjects in this study. We are also grateful to the phlebotomists and clinical laboratory technicians for their valuable assistance with blood collection and biochemical analyses.