Supine lower body negative pressure exercise simulates metabolic and kinetic features of upright exercise

Exercise within an artificial gravity environment may help prevent microgra vity-induced deconditioning. We hypothesized that supine lower body negativ e pressure (LBNP) exercise simulates physiological and biomechanical featur es of upright exercise. Walking (4.5 +/- 0.3 km/h) and running (8.0 +/- 1.0 km/h) while supine within a LBNP exerciser were compared with walking and running while upright. Eight healthy subjects exercised for 5 min at each o f the four posture/gait conditions. LBNP of 52 +/- 4 mmHg generated one bod y weight of supine ground reaction force (GRF). Gait parameters and GRFs we re measured during the third minute of exercise, and heart rate and oxygen consumption were measured during the fifth minute. Oxygen consumption durin g supine LBNP treadmill exercise [walking: 14.6 +/- 0.9; running: 32.2 +/- 1.6 (SE) ml.min(-1).kg(-1)] was similar to that during upright treadmill ex ercise (walking: 15.1 +/- 0.9; running: 34.0 +/- 1.9 ml.min(-1).kg(-1)). He art rate for supine LBNP exercise (grand mean: 133 +/- 11 beats/min) was al so similar to that for upright exercise (136 +/- 11 beats/min). Footward fo rces integrated over each stride (330.5 +/- 34.4 vs. 319.1 +/- 29.6 N . s) and rate of force generation (26,483 +/- 4,310 vs. 25,634 +/- 4,434 N/s) we re similar for upright and LBNP exercise, respectively. Our collective resu lts indicate that supine exercise within LBNP can simulate the physiologica l stress and GRFs that are generated during upright gait.