Objective: To derive regression equations using lower leg length (knee height) or arm span to predict height, and equations using ratios of weight/lower leg length or weight/arm span to predict body mass index and % body fat.
Subjects: Determination sample of 78 men and 82 women aged 17-70 years, and validation sample of 53 men and 121 women aged 18-82 years.
Measurements: Height, weight, lower leg length measured from the top of the patella with knee flexed at 90 degrees, arm span, % body fat by densitometry, and age.
Results: Lower leg length gave good prediction of height (men: r2 = 79%, SEE = 3.2 cm; women: r2 = 73%, SEE = 3.4 cm). Weight/lower leg length ratio was highly predictive of body mass index (men: r2 = 95%, SEE = 1.1 kg/m2, women: r2 = 94%, SEE = 1.1 kg/m2), and gave an estimation comparable to that of body mass index for predicting % body fat (men: r200 = 68%, SEE = 5.0% of body weight; women: r2 = 72%, SEE = 4.6% of body weight). Applying these equations based on lower leg length and weight/lower leg length ratio to a separate sample of men and women showed 95% of the errors of height estimate were within 6.5 cm, and of body mass index estimate were within 2 kg/m2. The same analysis of arm span showed the errors of body composition prediction were unacceptably high.
Conclusion: Lower leg length is useful for estimating body composition when height measurement is not available.