ALTERATIONS IN MUSCULAR PERFORMANCE AND ORTHOSTATIC TOLERANCE DURING RAMADAN

Background: During Ramadan, physiological changes are expected to resu lt from both long-term dietary restriction and partial sleep loss. Hyp othesis: We speculated that Ramadan lasting has deleterious effects on muscle performances and on orthostatic tolerance. Methods: There were 11 senior fighter pilots tested on three occasions during the first w eek of Ramadan (Beg-R), during the fourth week (End-R) and during a co ntrol period, 2 mo after Ramadan (C). Each test session consisted of a n assessment of the strength and endurance performances of the knee ex tensors and elbow flexors and of an analysis of the HR and BP response s to the orthostatic stress imposed by a 80 degrees head-up tilt. Resu lts: Body weight decreased by 2.7% at End-R in comparison with C perio d (p < 0.01). Maximum isometric strength (MVC) of elbow flexor muscles decreased immediately (by 10-12%; p < 0.05). Muscular endurance at bo th 35 and 70% MVC were lower at End-R in comparison with C period (-28 %, -22%, respectively; p < 0.05). The head-up tilt test at End-R was a ccompanied by a higher increase in heart response than during orthosta sis during C and Beg-R periods, and by a decrease in pulse pressures ( p < 0.001). These alterations in responses to the head-up tilt were as sociated with a fall by about 7% in plasma volume. Conclusions: These data demonstrate that Ramadan fasting leads to an impairment in muscul ar performances and to a decrease in orthostatic tolerance. Further st udies are needed to verify the impact of these changes on +Gz toleranc e.