Strength & Conditioning

Document Type



The purpose of this study was to determine the association between weight-bearing index (WBI) and ACTN3 genotype in male college students. Subjects were healthy male college students aged 18 to 21 years old. The maximal static forces of knee extension (leg strength) of the subjects were measured, and WBI was calculated by dividing the leg strength by the subjects’ body weight. Genomic DNA was extracted from each subject using hair strands, and its base sequence determined genotypes in RR, RX, and XX. Welch-type ANOVA revealed that WBI in the XX type was greater than in the RR and RX types despite no significant difference in leg strength and lean body mass among genotypes. Although it is difficult to find apparent or direct evidence to explain this result, some inferences can be proposed, such as compensatory force exertion based on its muscle fibers, regulation in calcineurin via the α-actine-2 gene, or functional enhancement of myoglobin-based endurance slow muscles in XX type may increase muscular activities against gravity, making WBI greater.