Coach-Supervised Periodized Training Versus Self-Directed Training in Amateur Swimmers: A Six-Month Prospective Cohort Study

Background/Objectives: This prospective observational study compared six-month changes in body composition, exercise performance, and cardiorespiratory fitness between amateur swimmers following coach-supervised periodized training and swimmers training independently. Methods: Twenty healthy men aged 40–60 years were enrolled in a coach-supervised master-swimmer group (MS; n = 10) or a self-directed leisure-swimmer group (LS; n = 10). Both groups swam three times per week and reported similar total training volumes. Anthropometry, body composition, dietary intake, and cardiopulmonary responses during an incremental treadmill test were assessed before training (T0) and after six months (T6). Results: Total exercise time and maximal treadmill speed increased numerically in both groups, with no significant between-group differences (p > 0.05). The reported percentage changes in maximal oxygen uptake were 12.6 ± 14.0% in MS and 2.5 ± 5.4% in LS, while oxygen uptake at the anaerobic threshold changed by 16.8 ± 16.8% and 2.5 ± 5.4%, respectively (reported between-group p < 0.05). Body-composition changes did not differ significantly between groups. Conclusions: Coach-supervised periodized training was associated with larger improvements in aerobic-fitness indices than self-directed training of broadly similar volume.