Buskirk E R, Mendez J
Med Sci Sports Exerc. 1984 Dec;16(6):584-95.
Because we are unsure of many of the constants that we use in the calculation of components of body composition, there is a need for a greater number of postmortem analyses in order to prepare better equations for more accurate utilization of indirect noninvasive measurements. At present, most investigators who study active people (including athletes) use techniques that only provide an approximation of body fatness. Because excess fat serves as a burden to the body during transport in the performance of many physical activities, fatness constitutes a variable of concern. Fat-free body weight is usually calculated by difference and serves as a reference for some physiological functions. Although fat-free weight and lean body mass are not the same, most investigators calculate fat-free weight and many use the terms interchangeably. Some of the assumptions and problems in utilizing hydrodensitometry in the calculation of body fatness remain unresolved, such as the true densities of the different gross components of body composition in the young, aged, physically fit, etc. A variety of body composition profiles of different athletes have been published in recent years, which substantially augment efforts initiated in the 1940s and 1950s. The regular employment of a total body water assessment along with hydrodensitometry would improve the accuracy of calculation of body fatness, but the procedure is somewhat expensive in cost and time of subject involvement. In order to extend our knowledge of body composition and to quantitatively ascertain the mass of skeletal muscle, some of the procedures for calculating cell and muscle mass are reviewed including total body potassium, total body nitrogen, creatinine excretion, and 3-methylhistidine excretion. These procedures reveal important information, but require further investigation before we are confident that we are measuring cell or muscle mass. We have focused on 3-methylhistidine excretion because preliminary investigation suggests that it may reveal differences in muscle mass not detected by densitometry.
由于我们不确定在身体成分组成计算中所使用的许多常数，因此需要进行更多的尸体分析，以便制定出更好的公式，从而更准确地利用间接非侵入性测量方法。目前，大多数研究活跃人群（包括运动员）的研究者所使用的技术，仅能提供对身体脂肪含量的一个近似值。由于在许多体育活动的进行过程中，过多的脂肪会成为身体运动时的负担，所以脂肪含量是一个值得关注的变量。无脂肪体重通常通过差值计算得出，并作为一些生理功能的参考指标。尽管无脂肪体重和瘦体重并不相同，但大多数研究者计算无脂肪体重时，很多时候会将这两个术语互换使用。在利用水下密度测量法计算身体脂肪含量时，一些假设和问题仍未得到解决，比如不同年龄段、身体状况良好的人群等身体成分中不同总体成分的真实密度。近年来，已经发表了各种不同运动员的身体成分概况，这极大地推动了始于20世纪40年代和50年代的相关研究工作。将全身水评估与水下密度测量法常规结合使用，会提高身体脂肪含量计算的准确性，但该方法在成本和受试者参与时间方面都有些昂贵。为了扩展我们对身体成分的认识，并定量确定骨骼肌的质量，本文回顾了一些计算细胞和肌肉质量的方法，包括全身钾、全身氮、肌酐排泄和3 - 甲基组氨酸排泄。这些方法揭示了重要信息，但在我们确信自己测量的是细胞或肌肉质量之前，还需要进一步研究。我们重点关注了3 - 甲基组氨酸排泄，因为初步研究表明，它可能揭示出密度测量法未检测到的肌肉质量差异。
