Effects of head-down tilt for 10 days on the compliance of the leg.
The purpose of this investigation was to measure lower leg compliance before, during and after a 10-day period of bedrest at head-down tilt to test the hypothesis that leg compliance and the capacity for venous pooling is increased by the adaptation to stimulated microgravity. Venous occlusion plethysmography with multiple proximal occlusion pressures was used to obtain compliance measurements in six male subjects. Calf circumference decreased significantly during the tilt (corresponding to a decrease in cross sectional area of 7%) and had not returned to baseline seven days after the end of tilt. Compliance post-tilt was significantly greater than pre-tilt, probably mainly due to a reduction in muscle mass. This study supports the need for investigations to define: (a) the degree of protection against orthostatic hypotension that can be achieved by maintaining leg muscle mass and tone, and (b) efficient and specific exercise programs to prevent loss of muscle mass and function-particularly during spaceflight.
Buckey
J C
JC
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9034.
Lane
L D
LD
Plath
G
G
Gaffney
F A
FA
Baisch
F
F
Blomqvist
C G
CG
D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D007866:Leg / Q000098:blood supply*; D008297:Male; D010953:Plasma Volume; D012039:Regional Blood Flow; D013026:Space Flight; D016683:Supine Position; D014655:Vascular Resistance; D014893:Weightlessness