Adaptability in Swimming Pattern: How Propulsive Action Is Modified as a Function of Speed and Skill

Relationship between swimming speed, intra-cycle variation of horizontal speed, and Froude efficiency during consecutive stroke cycles in adolescent swimmers

The purpose of this study was to investigate the relationship between swimming speed, intra-cycle variation of horizontal speed of displacement (dv), and Froude efficiency (ηF) in front-crawl during three consecutive stroke cycles. The sample consisted of 15 boys aged 16.07 ± 0.77 years and 15 girls aged 15.05 ± 1.07 years. Swimming speed, dv and ηF were measured during a 25 m front-crawl trial. Three consecutive stroke cycles were measured. Swimming speed showed a non-significant stroke-by-stroke effect (F = 2.55, p = 0.087, η2 = 0.08), but a significant sex effect (F = 90.46, p < 0.001, η2 = 0.76). The dv and ηF had the same trend as the swimming speed for the stroke-by-stroke effect, but a non-significant sex effect (p > 0.05). The Spearman correlation matrix between swimming speed and dv, and swimming speed and ηF showed non-significant correlations for the three stroke cycles in both sexes. However, the tendency of the former was not always inverse, and the latter was not always direct. Coaches and swimmers need to be aware that lower dvs are not always associated with faster swimming speeds and vice-versa, and that ηF is a predictor of swimming speed, not dv.

Association between elite swimmers' force production and 100 m front crawl inter-lap pacing and kinematics

The present study aimed to analyse the associations between force production and 100 m front crawl inter-lap pacing and kinematics. Eleven elite male swimmers performed a 100 m front crawl maximal effort to collect 50 m lap time (T₅₀, s) and velocity (v, m·s^-1) for pacing, stroke rate (SR), stroke length (SL) and stroke index (SI) as kinematic variables. A 30 s tethered effort allowed to determine the peak (F_peak) and mean force (F_mean) as force production variables. The relative change (Δ) between 50 m laps was also calculated for all measures. A paired sample t-test was used to check differences between laps and Pearson correlation coefficients allowed to quantify the associations between force and remaining variables. The T₅₀ increased from the first to the second lap (ΔT₅₀ = 10.61%, p < 0.01, d = 2.68), while v (Δv = -5.92%, p < 0.01, d = 1.53), SR (ΔSR = -6.61%, p < 0.01, d = 0.45) and SI (ΔSI = -4.92%, p = 0.02, d = 0.45) decreased. SL remained unchanged between laps (ΔSL = 1.07%, p = 0.66, d = 0.08). No associations were found between force production and most of Δ, with the only exception being the reasonable good association between F_peak and Δv (r = 0.62, p = 0.04). Although both pacing and kinematics fall from the first to the second sections of a 100 m front-crawl effort, the swimmers who exhibit higher F_peak show a more stable front crawl v between both 50 m laps.

Vision-Based System for Automated Estimation of the Frontal Area of Swimmers: Towards the Determination of the Instant Active Drag: A Pilot Study

Swimmers take great advantage by reducing the drag forces either in passive or active conditions. The purpose of this work is to determine the frontal area of swimmers by means of an automated vision system. The proposed algorithm is automated and also allows to determine lateral pose of the swimmer for training purposes. In this way, a step towards the determination of the instantaneous active drag is reached that could be obtained by correlating the effective frontal area of the swimmer to the velocity. This article shows a novel algorithm for estimating the frontal and lateral area in comparison with other models. The computing time allows to obtain a reasonable online representation of the results. The development of an automated method to obtain the frontal surface area during swimming increases the knowledge of the temporal fluctuation of the frontal surface area in swimming. It would allow the best monitoring of a swimmer in their swimming training sessions. Further works will present the complete device, which allows to track the swimmer while acquiring the images and a more realistic model of conventional active drag ones.

A Multidisciplinary Comparison of Different Techniques Among Skilled Water Treaders

In an immersion incident, a person may be required to tread water for extended periods of time in order to survive. Treading water, or maintaining a stable head position above the water surface, can be achieved in several different ways. Determining which treading water techniques are economic (energetically and cognitively) is an important first step in approaching evidence-based water safety instruction. The present study investigated the cognitive and metabolic demands associated with four main techniques for treading water in experienced water treaders. Skilled water treaders (n=21) performed four common treading techniques for 3min each: "running" in the water, "flutter kick" with hands sculling, "upright breaststroke," and "egg-beater." Self-reported rate of perceived exertion (RPE) and task load index (TLX) score, as well as objective measures of probe reaction time (PRT; i.e., response to auditory cues while treading), oxygen consumption and heart rate were assessed. The "egg-beater" technique and the "upright breaststroke" technique were linked to significantly lower cognitive and energetic demands compared to the other techniques (VO₂: p<0.001 - "Running" M=29.02, SD=7.40/"Flutter kick" M=29.37, SD=8.56, "Breaststroke" M=23.47, SD=7.28, and "Eggbeater" M=23.18, SD=6.31). This study lays the groundwork for future research that may establish the ideal movement behavior in drowning situations and investigate movement instruction to less experienced treaders.