EFFECTS OF MICROGRAVITY ON MUSCULAR EXPLOSIVE POWER OF THE LOWER-LIMBS IN HUMANS

The maximal explosive power of the lower limbs of one astronaut has be en measured before launch, and 2, 6 and 11 days after re-entry from 31 days on the MIR Station (EUROMIR'94). The subject, sitting on the car riage-seat of a Multipurpose Ergometer-Dynamometer (MED) constructed a d hoc in our laboratory, pushed maximally with both feet on two force platforms (knees angle 110 degrees). The carriage was free to move bac kwards on two rails inclined 20 degrees upwards. The force (F) of the lower limbs and the speed of the carriage (v) were recorded and the in stantaneous mechanical power (w) was calculated as w = F v. The aver age value of the mechanical power (w(max)) throughout the explosive ef fort was then obtained. The overall duration of the push was on the av erage about 0.3 s. It was observed that, at day R + 2, mean force, max imal velocity, maximal power (mean and peak), maximal acceleration and overall mechanical work, were all reduced between 60 and 80% of pre-f light values. However, the recovery was remarkably fast, since all the se parameters attained about 90% of pre-flight values by day R + 11.