Park Y S, Pendergast D R, Rennie D W
Undersea Biomed Res. 1984 Jun;11(2):159-68.
Steady-state body insulation was measured in 7 healthy male subjects during rest and exercise for 3 h in water of 28 degrees C - 32 degrees C. At rest, maximal body insulation increased as a linear function of mean subcutaneous fat thickness by an amount approximately 4-fold what would be predicted from the physical insulation of fat alone. With arm plus leg exercise, body insulation declined as an exponential function of the exercise intensity, reaching approximately 25% of the resting value at work loads above VO2 = 1.2 liters.min-1. During exercise the relationship between overall body insulation and mean subcutaneous fat thickness was almost identical to that predicted from fat insulation and mean subcutaneous fat thickness was almost identical to that predicted from fat insulation alone. These results suggest that 75% of maximal body insulation in resting subjects is achieved by use of skeletal muscle as an insulative barrier and that the muscle component is increased with increasing fat thickness. This muscle insulation shell is lost during exercise. As a practical consequence, heat generated by muscular exercise in water colder than critical water temperature cannot offset cooling unless the exercise intensity is great.
在28摄氏度至32摄氏度的水中，对7名健康男性受试者在休息和运动3小时期间的稳态身体隔热情况进行了测量。在休息时，最大身体隔热随着平均皮下脂肪厚度呈线性增加，增加量约为仅根据脂肪的物理隔热所预测值的4倍。进行手臂加腿部运动时，身体隔热随着运动强度呈指数下降，在高于VO2 = 1.2升·分钟-1的工作负荷下，降至休息值的约25%。运动期间，全身隔热与平均皮下脂肪厚度之间的关系几乎与仅根据脂肪隔热所预测的关系相同。这些结果表明，休息受试者最大身体隔热的75%是通过将骨骼肌用作隔热屏障实现的，并且肌肉成分会随着脂肪厚度增加而增加。这种肌肉隔热层在运动期间会消失。实际情况是，在水温低于临界水温时，除非运动强度很大，否则肌肉运动产生的热量无法抵消散热。
