Objectives Fat tissue does not directly contribute to an increase in propulsive force in swimming, though it has the potential to indirectly enhance swimming performance by reducing active drag as the specific gravity of fat tissue is lower than that of water. However, the relationship between body composition and active drag has not been elucidated. This study aimed to evaluate how body composition relates to active drag during arms-only front crawl swimming. Design Cross-sectional study. Methods Twenty-two male collegiate swimmers (height, 1.73±0.06m; body mass, 67.6±6.0kg) performed arms-only front crawl swimming using a measuring active drag (MAD)-system. Active drag was evaluated at 1.20, 1.50m/s, and maximum swimming velocity. Body composition data, fat mass (FM), fat-free mass (FFM), and the percentage of FM relative to body mass (%FM) were measured using dual-energy X-ray absorptiometry within 24h of the MAD-system experiment. The associations between body composition data and active drag were evaluated using Pearson's correlation coefficients. Results The results indicated that %FM was negatively correlated with active drag at 1.20 and 1.50m/s, whereas FFM was positively correlated with active drag at 1.50m/s. Conclusions In male swimmers with %FM between 6.3 and 12.0%, a higher %FM, reflecting lower body density, had lower active drag at submaximal swimming velocities. These findings suggest that swimmers and their coaches should consider the balance of FM and FFM from the perspective of active drag rather than unnecessarily decreasing FM or increasing FFM to enhance swimming performance. Practical implications • For male competitive swimmers with whole body fat mass as a percentage of body mass (%FM) between 6.3 and 12.0%, active drag at submaximal swimming velocities is lower in swimmers with higher %FM in arms-only front crawl swimming. • Swimmers with higher fat-free mass may have an advantage in increasing propulsive power and force in 25m maximal effort trial, while the maximum swimming velocity is not associated with any body composition variable. • Swimmers and coaches should strategically tailor the balance of fat mass and fat-free mass according to their speciality events rather than unnecessarily bulking up muscles to enhance their strength.
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