Objective: This study examines the effects of Ramadan fasting on endurance performance.
Method: Using a crossover design, 10 moderately trained, active Muslim men performed 60 min runs on a treadmill in the fasted (Ramadan, RAM) and non-fasted (Control, CON) state on two separate counterbalanced occasions. After familiarization, four subjects performed their CON trial 1 week before Ramadan, while the other six subjects performed their CON trial 1 week after the Ramadan month. The subjects' last meals were standardised before their exercise trials. The 60 min continuous endurance running criteria test consisted of 30 min preloading run at 65% maximum oxygen consumption (Vo(2max)) intensity speed, followed by another 30 min time trial (TT) where subjects manually adjusted their speeds so as to cover the greatest possible distance.
Results: Subjects ran significantly further during the 30 min TT run in the CON compared to RAM condition (5649+/-715 vs 5448+/-847 m, p=0.023). Blood glucose concentration was significantly lower (4.5+/-0.3 vs 4.9+/-0.4 mmol/l, p=0.003) and urine specific gravity was significantly higher (1.018+/-0.006 vs 1.006+/-0.004, p=0.001) at the start of exercise in the RAM condition than in CON. Physiological responses during the 30 min TT run (mean heart rate, blood lactate and ratings of perceived exertion) were, however, not significantly different between the two conditions (all p>0.05). There were also no significant differences in the subjects' daytime sleepiness or mood profile between the RAM and CON conditions (all p>0.05).
Conclusion: Ramadan fasting has a small yet significant negative impact on endurance running performance, although the impact varies across individuals.