Effects of Ramadan intermittent fasting on middle distance running performance in well trained runners

International audienceObjective: To assess whether Ramadan intermittent fasting (RIF) affects 5000m running performance and physiological parameters classically associated with middle distance performance.Design: Eighteen subjects (age 23.6±2.9 yr, body mass 64 ± 2.3 kg) divided in two experimental groups (Ramadan fasting (n = 9 vs. control, n= 9) participated in two experimental sessions, one before RIF and the other the last week of fasting.Setting: For each session subjects completed four tests in the same order: a maximal running test, a maximal voluntary contraction (MVC) of knee extensor, two rectangular submaximal exercises on treadmill of 6 min duration at an intensity corresponding to the first ventilatory threshold (VT1) and a running performance test (5000m).Participants: 18 well-trained middle distance runnersMain Outcome Measurements: Maximal oxygen consumption, maximal voluntary contraction, running performance, running efficiency submaximal VO2 kinetics parameters (basal VO2 : VO2b, time constant : τ, and amplitude : A1) and anthropometric parameters were recorded or calculated.Results: At the end of Ramadan fasting a decrease in maximal voluntary contraction was observed, (-3,2%, p< .00001, Eta2: 0.80), associated with an increase in time constant of oxygen kinetics (+51%, p< .00007, Eta2: 0.72) and a decrease in performance (-5%, p< .0007, Eta2: 0.51). No effect was observed on running efficiency or maximal aerobic power.Conclusions: These results suggest that Ramadan changes in muscular performance and oxygen kinetics could affect performance during middle distance events and need to be considered to choose training protocols during RIF