F-12J Free Communication/Thematic Poster Space Flight and Bed Rest Deconditioning
Previous studies reported significant decreases in lower-extremity strength and endurance after long-duration space flight. Limited data have been reported regarding upper body strength and endurance, which may be important to extravehicular activity and mission success.
The purpose of this study was to determine whether U.S. crewmembers currently perform sufficient amounts of upper-body resistive exercise and arm ergometry in flight to prevent losses of upper-body strength and endurance as well as arm lean-muscle mass (ALM) during long stays on the International Space Station (129–196 days).
Bench press one repetition maximum (1RM) was estimated from a 4–6RM measured using a Smith machine. Total number of repetitions (TRM) was measured during a two-minute push-up test and during pull-ups to volitional fatigue. Six US crewmembers (5 males, 1 female) were tested 180d (L-180) and 30–45d (L-30) days before flight and 5–7d (R+7) after flight. Bodyweight (BW) and DEXA-determined right and left ALM were measured at L-30 and R+7. The mean of measurements (1RM, TRM) made at L-180 and L-30 was accepted as representative of preflight performance. Pre- to postflight TRM, 1RM, BW and ALM were analyzed using paired t-tests.
Pushups TRM (56 + 0.8 vs 45 + 5), pull-ups TRM (11 + 0.1 vs 10 + 0.1) and bench press 1RM (66.3 + 10.0 kg vs 60.4 + 7.3 kg) were not different pre- to postflight (p > 0.05). Although there was a significant decrease in BW (74.5 + 3.9kg vs 71.3 + 3.9 kg, p < 0.05), performance measures normalized for BW remained unchanged. ALM (6.5 + 0.6 kg vs 6.4 + 0.7 kg) did not change pre- to postflight.
U.S. crewmembers appear to be maintaining upper-body strength and endurance during flight using the current countermeasures program. Measurement of upper-body performance should be continued in case mission activities interfere with scheduling of exercise countermeasures.