title: Circulation and respiration response to arm exercise and lower body negative pressure.
abstract: The effects of supine arm exercise and lower body negative pressure (LBNP) were studied in six subjects with 10 min of LBNP at -40 mmHg (L), arm cranking for 8 min at a work load of 225 kpm/min (E) and both combined (L + E) preceded by 2 min of LBNP. Initial responses of ventilation (VI) and VO2 were curtailed and heart rate was significantly higher after the first min of L + E than E, reflecting the less accessible venous reservoir and reduced stroke volume due to L. Leg volume was significantly reduced after 30 s of E and continued to decline and remained below baseline during 6 min of recovery. With L + E, leg volume remained constant after E began, indicating both a shift of blood from legs to arms and reduced extra-vasation with LBNP. End-tidal PO2, VI and VI/VO2 were higher and PCO2 lower during the latter stages of L + E than during E, indicating less effective lung perfusion and greater alveolar deadspace caused by LBNP. The release of pooled blood from the lower body after L + E caused a greater VI, VO2 and lower RE than after E and produced marked transients in PCO2 and PO2, thereby slowing the recovery of gas exchange.
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D001775:Blood Circulation; D001810:Blood Volume; D006112:Gravitation; D006339:Heart Rate; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D005082:Physical Exertion; D011187:Posture; D012119:Respiration