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Guilliams, M E.1; Lee, S M.C.1; Shepherd, B1; Chauvin, J1; Taddeo, T1; Shackelford, L C.1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S262
F-12J Free Communication/Thematic Poster Space Flight and Bed Rest Deconditioning

1Wyle Laboratories and NASA-Johnson Space Center, Houston, TX

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.

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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).

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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.

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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.

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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.

©2003The American College of Sports Medicine