Oxygen uptake kinetics and biological age in relation to pulling force and 400-m front crawl performance in young swimmers.

The study aimed to assess differences in the biological age () of 13-year-old swimmers and show their ability, as biologically younger- or older-, to develop fast 60-s oxygen uptake () kinetics and tethered swimming strength. Furthermore, the interplay between swimming strength, , and 400-m front crawl race performance was examined. The study involved 36 competitive young male swimmers (metrical age: 12.9 ± 0.56 years). Depending on examination, the group was divided into (: 15.8 ± 1.18 years, = 13) and (: 12.9 ± 0.60 years, = 23) participants, especially for the purpose of comparing tethered swimming indices, i.e., average values of force ( ) and (breath-by-breath analysis) kinetic indices, measured simultaneously in 1-min tethered front crawl swimming. From the 400-m racing stroke rate, stroke length kinematics was retrieved. In the 1-min tethered front crawl test, swimmers obtained higher results of absolute values of and . Conversely, when was present relatively to body mass and pulling force (in ml∙min∙kg∙N), swimmers showed higher relative usage. swimmers generally exhibited a slower increase in during the first 30 s of 60 s. , , , and basic swimming kinematic stroke length were significantly interrelated and influenced 400-m swimming performance. The 1-min tethered swimming test revealed significant differences in the homogeneous calendar age/heterogeneous group of swimmers. These were distinguished by the higher level of kinetics and pulling force in individuals and lower efficiency per unit of body mass per unit of force aerobic system in peers. The higher kinetics and tethered swimming force were further translated into 400-m front crawl speed and stroke length kinematics.