Impact of energetic-anthropometric features on 50-m and 100-m freestyle kinematic indices in young male swimmers

<i>Purpose</i>: The determinants of the sports results of young and adult swimmers differ, especially in sprint races (50-100 m). Their identification can be used to assess the athlete's potential and to set appropriate requirements. The aim was to distinguish energy-anthropometric profiles (clusters) among young athletes and to characterize their kinematic indices in freestyle sprint races (50-100 m). Kinematic variables from both distances were compared in each cluster. <i>Methods</i>: Anthropometric indices and mechanical power of the upper limbs (arm-cranking) were determined in 43 subjects (boys, aged 12-13 years), which were used for cluster analysis. For the 50- and 100-m races the following were determined: velocity (<i>v</i>), stroke rate (SR), stroke length (SL) and stroke index (SI). Comparative analysis was performed between clusters and between distances. <i>Results</i>: The following clusters were distinguished: Large (LSP), Medium (MSP) and Small Size and Power (SSP), which differed due to anthropometric and power indices. Intergroup differences (LSP, MSP and SSP, respectively) were revealed in <i>v</i> ₅₀ (1.65, 1.55, 1.49 m/s), <i>v</i> ₁₀₀ (1.52, 1.41, 1.34 m/s), SL₁₀₀ (1.92, 1.77, 1.72 m), SI₅₀ (2.92, 2.65, 2.54 m/s²), SI₁₀₀ (2.91, 2.51, 2.31 m/s²). In all clusters differences were revealed between <i>v</i> ₅₀ and <i>v</i> ₁₀₀ and SR₅₀ and SR₁₀₀. Differences in SL₅₀ and SL₁₀₀ were noticed in LSP and MSP, while in SI₅₀ and SI₁₀₀ in MSP and SSP. <i>Conclusions</i>: The evaluation of the technique should consider the energy-anthropometric profile of the athlete. The swimming technique need to be modified depending on the distance - also in races perceived as sprints.