Abstract
The aim was to compare the anthropometrics, biomechanics and energetics in young swimmers of different competitive levels. Seventy-five boys aged between 11 and 13 years-old with a broad range of performances were ranked based on their personal best time in the men’s 100m freestyle event and then split-up into three tiers (Tier-1, i.e., top-tier, best performers; Tier-2, mid-tier; Tier-3, lower-tier). A set of anthropometric features was measured (height, body mass, arm span and trunk transverse surface area). Stroke kinematics (speed, stroke length, stroke frequency) was assessed by a Speedo-meter. Swim efficiency was then estimated (stroke index, speed fluctuation, Froude efficiency). Hydrodynamics assessment encompassed the estimation of active drag and drag coefficient by velocity perturbation method and a set of dimensionless numbers (Froude, hull speed, Reynolds). Mechanical power (to overcome drag, transfer of kinetic energy to water, external power) and power input were derived. There was a significant variation with moderate effect sizes in all anthropometric features but the trunk transverse surface area. Tier-1 swimmers were taller, heavier and with longer limbs than remaining counterparts. There were also significant variations in the stroke kinematics with moderate-large effect sizes. Tier-1 swimmers showed higher stroke frequency, stroke length, speed, stroke index and propelling efficiency but lower speed fluctuations. Reynold number, Froude number and hull speed were significantly higher in Tier-1 swimmers, denoting large effect sizes. The mechanical power and power input delivered were significantly higher in tier-1 swimmers, showing moderate effect sizes. As a conclusion, it was noted significant variations, with moderate-large effect sizes, among the three tiers, for the vast majority of the selected variables. The better performances by tier-1 swimmers were related to their anthropometrics, biomechanics and energetics.
Highlights
In endurance sports, notably time-based events, the athlete aims to travel a given distance as quick as possible
The speed depends on energetics and biomechanics: v = Etot
Aerobic energy release is straightforward to be measured because there is a relationship between oxygen uptake measured by breathing and the whole-body aerobic production of ATP; while, methods to measure anaerobic sources are less reliable as anaerobic ATP production takes place at intracellular level, with little reliance on central processes (Gastin, 2001)
Summary
Notably time-based events, the athlete aims to travel a given distance as quick as possible. Where Etot is the total power input, Eaer the energy contribution by aerobic system, Eanaer−la by the anaerobic lactic system, and E ATP−PCr by the anaerobic alactic system. The 200 m event, the aerobic contribution has been reported as 60–65% (Capelli et al, 1998; Figueiredo et al, 2011) In all these researches anaerobic lactic contribution was estimated by blood measures and anaerobic alactic contribution by an analytical model. In a swimming event that takes just under 1 min (e.g., 100 m) the aerobic contribution to total energy expenditure is 30–45%, depending on the measuring techniques used. In order to deliver better performances, swimmers can either enhance Etot (energetics) and/or C (biomechanics). The aim was to compare the anthropometrics, biomechanics and energetics in young swimmers of different competitive levels. It was hypothesized that top-tier swimmers would have beneficial anthropometric traits, better biomechanical and energetics responses than low-tier counterparts
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