Acceleration with exercise during head-down bed rest preserves upright exercise responses.
BACKGROUND
This study was designed to elucidate the effect of short-arm centrifuge-induced artificial gravity with exercise training during ground-based simulated spaceflight, i.e., prolonged head-down bed rest (HDBR), on respiratory and cardiovascular responses to upright exercise.


METHODS
There were 10 healthy men who underwent 20 d of -6 degrees HDBR, and were assigned to either a countermeasure (CM) group (n = 5) or a no countermeasure (No-CM) group (n = 5). The subjects in the CM group performed two sessions (20 min each session, 40 min total) of short-arm centrifuge-induced artificial gravity with exercise training in a supine position on alternate days (10 d total) during HDBR. The first session was set at 0.8-1.4 G load at heart level with a constant exercise intensity (60 W), and the second session began with a 0.3 G load at heart level with an interval exercise protocol (40-80% peak oxygen uptake; VO2peak). The measurements of respiratory and cardiovascular responses to incremental exercise were performed pre- and post-HDBR.


RESULTS
The 20 d of HDBR increased minute expired ventilation, heart rate, and respiratory exchange ratio and decreased stroke volume during submaximal exercise in the No-CM group, whereas these parameters were unchanged in the CM group. In the No-CM group, VO2peak decreased significantly (47.0 +/- 8.6 to 34.8 +/- 6.8 ml x kg(-1) x min(-1), p < 0.05), whereas VO2peak in the CM group did not show a significant decrease following 20 d of HDBR (47.7 +/- 10.0 to 43.9 +/- 8.9 ml x kg(-1) x min(-1)). These results suggest that short-arm centrifuge-induced artificial gravity with exercise training is effective in maintaining respiratory and cardiovascular responses to upright exercise.
Katayama
Keisho
K
Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya 464-8601, Japan. katayama@htc.nagoya-u.ac.jp
Sato
Kohei
K
Akima
Hiroshi
H
Ishida
Koji
K
Takada
Hiroki
H
Watanabe
Yoriko
Y
Iwase
Mitsunori
M
Miyamura
Miharu
M
Iwase
Satoshi
S
D000293:Adolescent; D000328:Adult; D002498:Centrifugation; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D018472:Hypogravity / Q000009:adverse effects*; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance; D011187:Posture; D013026:Space Flight