Alterations in muscular performance and orthostatic tolerance during Ramadan.
BACKGROUND
During Ramadan, physiological changes are expected to result from both long-term dietary restriction and partial sleep loss.


OBJECTIVE
We speculated that Ramadan fasting has deleterious effects on muscle performances and on orthostatic tolerance.


METHODS
There were 11 senior fighter pilots tested on three occasions during the first week of Ramadan (Beg-R), during the fourth week (End-R) and during a control period, 2 mo after Ramadan (C). Each test session consisted of an assessment of the strength and endurance performances of the knee extensors and elbow flexors and of an analysis of the HR and BP responses to the orthostatic stress imposed by a 80 degrees head-up tilt.


RESULTS
Body weight decreased by 2.7% at End-R in comparison with C period (p < 0.01). Maximum isometric strength (MVC) of elbow flexor muscles decreased immediately (by 10-12%; p < 0.05). Muscular endurance at both 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 accompanied by a higher increase in heart response than during orthostasis 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 associated with a fall by about 7% in plasma volume.


CONCLUSIONS
These data demonstrate that Ramadan fasting leads to an impairment in muscular performances and to a decrease in orthostatic tolerance. Further studies are needed to verify the impact of these changes on +Gz tolerance.
Bigard
A X
AX
Unité de Bioénergétique et Environnement, Centre de Recherches du Service de Santé des Armées, La Tronche, France.
Boussif
M
M
Chalabi
H
H
Guezennec
C Y
CY
D000328:Adult; D000337:Aerospace Medicine; D001794:Blood Pressure; D001835:Body Weight; D005215:Fasting / Q000009:adverse effects*; D018475:Head-Down Tilt; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000209:etiology* / Q000503:physiopathology; D007514:Islam; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance; D010953:Plasma Volume; D011597:Psychomotor Performance / Q000502:physiology*