151 Growing up and reaching for the top: A longitudinal study of talented swimmers 7 Anthropometric measures Swimmers were measured for height, sitting height and body mass with 0.1 cm or 0.1 kg precision. Height was assessed using a stadiometer (Seca, 217, Seca GmbH & Co.KG, Germany), and sitting height was measured using a standard box (height 45 cm) positioned at the stadiometer’s base. Body mass was measured using a digital scale (Beurer, GS 300, Beurer GmbH, Germany). Measures were taken twice and conducted by the same two researchers. The mean value was documented. A third measure was taken if the difference between the first two exceeded 0.4 cm. The median was then recorded. Maturity status was estimated using a non-invasive method developed by Moore et al. (2015). This approach involves sex-specific calculations that determine the maturity offset of young adolescents, expressed in terms of years before or after Peak Height Velocity (YPHV). By subtracting YPHV from a swimmer’s chronological age, the predicted age of PHV (APHV) was calculated. However, it is important to acknowledge that accurately measuring biological maturity remains a challenging task, as highlighted by ongoing discussions in the literature that emphasize the complexities involved in this process (Malina et al., 2021) Countermovement Jump (CMJ) test Swimmers were instructed to perform two double-leg vertical countermovement jumps (CMJ) with arm swing, which is reported as a valid and reliable test to measure lower body power (Markovic et al., 2004). Lower body power is considered to be of particular importance during starts and turns, as it is in these moments that the lower extremities must generate the greatest impulse to achieve the highest accelerations off the block and wall, respectively (Keiner et al., 2021; Jones et al., 2018; West et al., 2011). The jumps began from an upright position, and there was a 30 s break between each trial to allow the swimmers to return to the starting position. Each trial was recorded with a vertical jump meter (Takei, TKK5406, Takei Scientific Instruments Co.,Ltd, Japan). The maximal jump height (in cm) was taken as indicator of lower body power and taken as outcome measure for further analyses (Gajewski et al. 2018). Mid-pool sprints Swimmers were instructed to perform one 25-m distance sprint at maximal swimming velocity. They initiated their effort from the midpoint of a 50-m pool, specifically at the 25-m mark. Starting from a static position, they immediately accelerated to full speed and maintained this pace until they touched the wall, signifying the completion of their effort. Swimmers performed the sprint effort in their best stroke, while wearing racing suits. Sprints were recorded with a digital video camera (HC-X1000 Camrecorder, Panasonic Netherlands, Netherlands), positioned on the lateral side of the pool at 15-m from the start. Kinematic data were collected by means of time video analysis. Maximal swimming
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