Sir.—In their study of serum cholesterol levels in prepubertal boys before and after a strength-training program, Weltman et al1 concluded that "a concentric strength-training program in prepubertal boys results in a reduction in serum cholesterol levels while maintaining the HDL-C [high-density lipoprotein cholesterol] level." This interesting study appears to have several methodologic problems that make such a conclusion difficult to justify.
Nineteen subjects were enrolled in a strength-training program while ten others were assigned to a control group. Nowhere is the reader told whether group assignment was randomized or whether such characteristics as body mass index, age, diet, and extracurricular habits of the two groups were similar. Prior to any intervention, the group assigned to the exercise program had a mean ( ± SD) serum cholesterol level substantially higher than that of the control group (5.09 ± 1.01 mmol/L [197.2 ± 39.3 mg/dL] vs 4.14 ± 0.56 mmol/L [159.9
MacMAHON JR. Effects of Strength Training on Serum Lipid Levels in Prepubertal Boys. Am J Dis Child. 1988;142(5):480–481. doi:10.1001/archpedi.1988.02150050018007