Shaffer-Bailey M, Greenleaf J E, Hutchinson T M
Ames Research Center, NASA, Moffett Field, CA 94035-1000, USA.
Aviat Space Environ Med. 1996 Jan;67(1):46-51.
To determine weight (water) loss levels for onset of muscular strength and endurance changes during deconditioning.
Seven men (27-40 yr) performed maximal shoulder-, knee-, and ankle-joint isometric (0 degree.s(-1) load) and isokinetic (60 degrees, 120 degrees, 180 degrees.s(-1) velocity) exercise tests during ambulatory control (AC), after 6 h of 6 degrees head-down tilt (HDT; dry-bulb temp. = 23.2 +/- SD 0.6 degrees C, relative humidity = 31.1+/- 11.1%) and after 6 h of 80 degrees foot-down head-out water immersion (WI; water temp. = 35.0 +/- SD 0.1 degree C) treatments.
Weight (water) loss after HDT (1.10 +/- SE 0.14 kg, 1.4 +/- 0.2% body wt) and WI (1.54+/- 0.19 kg, 2.0 +/- 0.2% body wt) were not different, but urinary excretion with WI (1,354 +/- 142 ml.6 h(-1)) was 28% greater (p < 0.05) than that of 975 +/- 139 ml.6 h(-1) with HDT. Muscular endurance (total work; maximal flexion-extension of the non-dominant knee at 180 degrees.s(-1) for 30 s) was not different between AC and the WI or HDT treatments. Shoulder-, knee-, and ankle-joint strength was unchanged except for three knee-joint peak torques: AC torque (120 degrees.s(-1), 285 +/- 20 Nm) decreased to 268 +/- 21 Nm (delta = -6%, p < 0.05) with WI; and AC torques (180 degrees.s(-1), 260 +/- 19 Nm) decreased to 236 +/- 15 Nm (delta = -9%, p < 0.01) with HDT, and to 235 +/- 19 Nm (delta = -10%, p < 0.01) with WI.
Thus, the total body hypohydration threshold level for shoulder- and ankle-joint strength and endurance decrements is more than 2% body weight (water) loss, while significant reduction in knee-joint muscular strength-endurance occurred only at moderate (120 degrees.s(-1) and lighter (180 degrees.s(-1)) loads with body weight loss of 1.4-2.0% following WI or HDT, respectively. These weight (water) losses and knee-joint strength decrements are somewhat less than the mean weight loss of 2.6% and knee-joint strength decrements of 6-20% of American astronauts after Skylab flights to 84 d.
确定在去适应过程中，肌肉力量和耐力开始发生变化时的体重（水分）流失水平。
七名男性（27 - 40岁）在动态对照（AC）期间、6小时6°头低位倾斜（HDT；干球温度 = 23.2 ± 标准差0.6°C，相对湿度 = 31.1 ± 11.1%）后以及80°脚向下头露出水面的水浸（WI；水温 = 35.0 ± 标准差0.1°C）处理6小时后，进行了最大肩部、膝部和踝关节等长（0度·秒⁻¹负荷）和等速（60度、120度、180度·秒⁻¹速度）运动测试。
HDT后（1.10 ± 标准误0.14千克，1.4 ± 0.2%体重）和WI后（1.54 ± 0.19千克，2.0 ± 0.2%体重）的体重（水分）流失无差异，但WI后的尿量排泄（1354 ± 142毫升·6小时⁻¹）比HDT后的（975 ± 139毫升·6小时⁻¹）高28%（p < 0.05）。AC与WI或HDT处理之间的肌肉耐力（总功；非优势膝在180度·秒⁻¹下最大屈伸30秒）无差异。肩部、膝部和踝关节力量无变化，但有三个膝关节峰值扭矩除外：AC扭矩（120度·秒⁻¹，285 ± 20牛米）在WI后降至268 ± 21牛米（变化量 = -6%，p < 0.05）；AC扭矩（180度·秒⁻¹，260 ± 19牛米）在HDT后降至236 ± 15牛米（变化量 = -9%，p < 0.01），在WI后降至235 ± 19牛米（变化量 = -10%，p < 0.01）。
因此，肩部和踝关节力量及耐力下降的全身脱水阈值水平超过2%体重（水分）流失，而膝关节肌肉力量耐力的显著降低仅在中等（120度·秒⁻¹）和较轻（180度·秒⁻¹）负荷下分别在WI或HDT后体重减轻1.4 - 2.0%时出现。这些体重（水分）流失和膝关节力量下降略低于美国宇航员在天空实验室飞行84天后平均2.6%的体重减轻和6 - 20%的膝关节力量下降。
