Integrated resistance and aerobic exercise protects fitness during bed rest.
BACKGROUND
The current exercise countermeasures have not fully protected astronauts' preflight aerobic and muscular fitness levels during International Space Station (ISS) missions, prompting a need to optimize the exercise prescription to improve or maintain astronauts' ability to perform critical tasks and eventually extend the duration of missions.


OBJECTIVE
To test the hypothesis that an integrated resistance and aerobic exercise prescription performed with exercise equipment similar to that on the ISS can be tolerated and maintain cardiovascular and muscular fitness during 14 d of exposure to a model of microgravity.


METHODS
Subjects (n = 9) participated in 14-21 d of pre-bed rest training and familiarization, 14 d of bed rest + iRAT exercise, and 7 d of ambulatory recovery. Peak aerobic capacity (V˙O2peak), ventilatory threshold (VT), and isokinetic and leg press tests were performed before and after bed rest to evaluate cardiovascular and muscle functions. Muscle cross-sectional area (CSA) was determined before, during, and after bed rest using magnetic resonance imaging (MRI).


RESULTS
Improvements from before to after bed rest were observed in V˙O2peak (2.8 ± 0.2 to 3.2 ± 0.2 L·min(-1)), VT (1.9 ± 0.2 to 2.1 ± 0.2 L·min(-1)), leg muscle power (1582 ± 317 to 1740 ± 359 W), and muscle CSA of the grouped vastus lateralis, vastus intermedius, and vastus medialis muscles (67.5 ± 8.4 to 68.9 ± 8.3 cm). Muscle strength and total CSA of the upper and lower legs were not different from before to after bed rest.


CONCLUSIONS
This is the first report of exercise being completely effective for the prevention of cardiovascular and skeletal muscle deconditioning during strict bed rest using exercise equipment similar to that on the ISS. This was accomplished with high subject compliance.
1Universities Space Research Association, Houston, TX; 2University of Houston, Houston TX; and 3Wyle Science, Technology and Engineering Group, Houston, TX.
Lori L
LL
Ploutz-Snyder
Meghan
M
Downs
Jeffrey
J
Ryder
Kyle
K
Hackney
Jessica
J
Scott
Roxanne
R
Buxton
Elizabeth
E
Goetchius
Brent
B
Crowell
D000328:Adult; D000337:Aerospace Medicine; D001510:Bed Rest / Q000009:adverse effects*; D018493:Cardiovascular Deconditioning; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength; D009929:Organ Size; D010101:Oxygen Consumption; D064797:Physical Conditioning, Human / Q000295:instrumentation / Q000502:physiology*; D010809:Physical Fitness; D052097:Quadriceps Muscle / Q000473:pathology* / Q000503:physiopathology; D055070:Resistance Training / Q000295:instrumentation; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects