Zamparo P, Antonutto G, Capelli C, Francescato M P, Girardis M, Sangoi R, Soule R G, Pendergast D R
Dipartimento di Scienze e Tecnologie Biomediche, Sezione di Fisiologia, Udine, Italy.
Scand J Med Sci Sports. 1996 Oct;6(5):273-80. doi: 10.1111/j.1600-0838.1996.tb00470.x.
Two forces act on a human body motionless in water: weight (W) and buoyancy (B). They are applied to the center of mass (CM) and to the center of volume (CV) of the subject, respectively. CM and CV do not coincide; this generates a torque that is a measure of the tendency of the upper part of the body to rise, rotating around its center of mass. To quantify this tendency, Pendergast & Craig defined 'underwater torque' (T') as the product of the net force with which the feet of a subject lying horizontally in water tend to sink, times the distance between the feet and the center of volume of the lungs. In this paper we have investigated: (a) the relationships between T' and body weight (BW), height (H), body surface area (BS), body density (BD) and leg density (LD) in a group of 30 subjects (group A, 14 females and 16 males, age range 16-50 years); and (b) the effect of gender and growth on T' in a group of 110 subjects (group B, 67 girls and 43 boys, age range 12-17 years). In group A, T' was found to be linearly related with BW (r=0.833, P<0.001), H (r=0.803, P<0.001), BS (r=0.866, P<0.001), BD (r=0.617, P<0.001) and LD (r=0.549, P<0.005). A multiple linear regression analysis showed that BS and BD explained about 85% of the variability of T' (r2=0.85). In group B, T' was found to increase linearly with age (r=0.47, P<0.01), the increasing rate being three times higher in boys compared with girls. As a consequence, the T' ratio between boys and girls increased with age, from 1.69 at 13 years to 2.04 at 16 years.
重力（W）和浮力（B）。它们分别作用于人体的质心（CM）和体积中心（CV）。质心和体积中心并不重合；这会产生一个扭矩，该扭矩衡量了人体上半部分围绕其质心上升的趋势。为了量化这种趋势，彭德加斯特和克雷格将“水下扭矩”（T'）定义为水平躺在水中的受试者双脚趋于下沉的净力乘以双脚与肺部体积中心之间的距离。在本文中，我们研究了：（a）在一组30名受试者（A组，14名女性和16名男性，年龄范围16 - 50岁）中，T'与体重（BW）、身高（H）、体表面积（BS）、身体密度（BD）和腿部密度（LD）之间的关系；以及（b）在一组110名受试者（B组，67名女孩和43名男孩，年龄范围12 - 17岁）中，性别和生长对T'的影响。在A组中，发现T'与BW（r = 0.833，P < 0.001）、H（r = 0.803，P < 0.001）、BS（r = 0.866，P < 0.001）、BD（r = 0.617，P < 0.001）和LD（r = 0.549，P < 0.005）呈线性相关。多元线性回归分析表明，BS和BD解释了T'变异性的约85%（r² = 0.85）。在B组中，发现T'随年龄呈线性增加（r = 0.47，P < 0.01），男孩的增加速率是女孩的三倍。因此，男孩和女孩之间的T'比值随年龄增加，从13岁时的1.69增加到16岁时的2.04。
