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.
This work was supported by the national funding through
the Portuguese Foundation for Science and Technology,
I.P., under the project UID/DTP/04045/2019, and European
Regional Development Fund (FEDER) under the COMPETE
2020 Programme for Competitiveness and Internationalization
(POCI) (POCI-01-0145-FEDER-006969). RB is an FCT-Ph.D.
scholar (SFRH/BD/142009/2018).
