Effects of HIIT and MICT on 100 m Swimming Performance and Stroke Kinematics in Adolescent Male and Female Competitive Swimmers

Adolescence is a critical period for swimmers, as it lays the foundation for both biological development and athletic performance. The effects of training loads on physiological, biomechanical, and technical parameters during this period highlight the importance of careful training planning. Water-based training interventions specific to swimming aim to support technical development and contribute to optimal performance. In this context, it is noteworthy that there is a significant gap in the literature regarding the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) approaches on stroke kinematic parameters in adolescent swimmers and the evaluation of these effects in the context of gender differences. The aim of this study is to compare the effects of 12-week HIIT and MICT training interventions on 100 m sprint swimming performance and stroke kinematic parameters and to examine the gender-related differences in these effects. The study included 42 competitive swimmers aged 12–17 (16 females, 26 males), who were randomly assigned to HIIT and MICT groups. Before and after the training period, the swimmers' 100 m performance was measured, along with stroke count (SC), stroke rate (SR), stroke length (SL), stroke index (SI), and stroke coordination (IdC) parameters. Both training protocols improved 100 m sprint performance (HIIT: p = 0.002, MICT: p = 0.007); however, the HIIT protocol showed more pronounced improvements in SI (p = 0.006) and IdC (p = 0.006) parameters, especially in female swimmers. In males, SI improvement was observed as a kinematic parameter in both groups (HIIT: p = 0.028, MICT: p = 0.043). HIIT and MICT training produced gender-specific differences in performance improvements and kinematic reflections in their chronic effects. The findings emphasise the importance of a gender- based approach in training planning for adolescent swimmers.