Associations Between Selected Biological Features and Absolute and Relative Swimming Performance of Prepubescent Boys Over a 3-Year Swimming Training Program: A Longitudinal Study.

The study aimed to investigate the effect of 3-year swimming training on selected biological variables in prepubescent male swimmers and to determine the best predictors of absolute (VSa) and relative (VSr) swimming velocity for 50 m and 400 m front crawl. Twenty-one 10-year old boys subjected to endurance swimming training (4 x 70 min per week) and 18 boys consisting a control group were assessed semi-annually for basic anthropometric and respiratory characteristics, breath-hold time (BHT), VO2max, leg explosiveness (HJ), and abdominal strength endurance (ASE). After three years of training, BHT (p < 0.001), VO2max (p < 0.01), HJ (p < 0.01) and ASE (p < 0.01) were greater in the swimmers than in the controls. VSa and VSr expressed as a percentage of baseline velocity increased more for the 50 m than for the 400 m distance (p < 0.001 and p < 0.01, respectively). The 50 m VSa and VSr positively correlated with those obtained for the distance of 400 m (in both cases p < 0.001). Baseline VSa was negatively correlated with the increase in absolute swimming velocity for both distances (50 m: r = -0.684, p < 0.001 and 400 m: r = -0.673, p < 0.001). The best predictors of VSa for 50 m and 400 m front crawl were HJ (r2 = 0.388; p < 0.001) and VO2max (r2 = 0.333; p < 0.001), respectively. The key predictors of VSr for both distances were age (50 m: r2 = 0.340, p < 0.001 and 400 m: r2 = 0.207, p < 0.001) and, after excluding it from analysis, HJ (50 m: r2 = 0.176, p < 0.001 and 400 m: r2 = 0.104, p < 0.001). These results suggest that regardless of prepubescent boys' initial abilities and exercise capacity, improvement in their swimming performance mainly depends on increases in power and neuromuscular coordination.

The Effect of Three-Year Swim Training on Cardio-Respiratory Fitness and Selected Somatic Features of Prepubertal Boys.

The data regarding somatic and physiological effects of sport-related physical activities in youth are limited. Moreover, whether exercise training is capable of increasing cardio-respiratory fitness remains a disputable issue. The study undertook to assess the effect of swimming training on cardio-respiratory fitness (CRF) and the development of physical traits in prepubertal boys, and to determine which of the traits is the best predictor of their CRF. Forty 10-year old prepubertal boys (10.5 ± 0.3 y) were divided into two groups (swimmers (SG), n = 20, and controls (CG), n = 20), which underwent anthropometric measurements and performed a 20 m shuttle run test (20 mSRT) semi-annually over a 3-year period. CRF indices (the number of 20 mSRT shuttles, maximal speed, and VO2max) were higher overall in the SG compared with the CG (p < 0.001). The values of the main physique variables increased faster in the CG, but the groups showed no differentiation of physical traits. In both groups, CRF indices were associated with the participants' physical traits, the most strongly with the sum of four skinfold thicknesses in the SG and knee breadth in the CG. These results suggest that swimming training is a form of additional physical activity that improves prepubertal boys' CRF but does not significantly affect their physical development. In using the 20 mSRT to assess the CRF of prepubertal boys, their physical activity level and age-related changes in body fatness need to be considered.