SEMG MEASUREMENTS ON LAND AND IN WATER PRIOR TO AND AFTER 60- 90 MINUTES OF SUBMERSION (SWIMMING) ARE HIGHLY RELIABLE

The purpose of this study was to investigate the reliability of surface electromyography (sEMG) measurements after being submerged (swimming) for 60-90 minutes. Isometric maximal voluntary contractions (MVC) on land and in water were collected of eight muscles in three males and three females (mean age 22.5±4.5 years). A paired samples t-test showed no significant differences in the mean MVC signal between pre and post test after prolonged water submersion (

Can You Swim in Waves? Children\u27s Swimming, Floating, and Entry Skills in Calm and Simulated Unsteady Water Conditions

Little is known about the transfer of swimming skills from indoor, flat, calm conditions to outdoor, wavy, unsteady conditions. The aim of the current study was to examine the differences in swimming, floating and entry skills in children between calm and simulated open water conditions. Sixty-six children, 11 years of age, were tested on two occasions, once in calm water and once in simulated open water conditions. Testing consisted of a 200 m time trial, a 3 min back floating test, a diving entry, and a rolling entry. The results show an 8% decrement in performance on the 200 m swim between calm and unsteady conditions for those who completed the 200 m under both conditions. When weaker swimmers, who only completed 50 m of the 200 m test distance were tested, the performance decrement rose to 14%. The diving entry, the rolling entry and the floating test had decrements of 16%, 21%, and 24%, respectively. We concluded that 11-year-olds should not be expected to reproduce swimming skills they have performed in calm water with the same proficiency in unsteady conditions during an emergency

KNEE AND ANKLE MUSCLES COACTIVATIONS IN BREASTSTROKE SWIMMING KICK AND RECOVERY: EXPLORATORY APPROACH

The specificities of body position in breaststroke induce important lower limbs solicitations for the swimmers to propel themselves efficiently. Coactivations around the knee and ankle might appear during the powerful leg extension (i.e. push) and for leg replacement (i.e. recovery). The purpose of this exploratory study is to determine muscle activations and coactivations during these two phases at three different velocities. The EMG of four muscles was recorded (BF, RF, GAS and TA). The results showed important activations of the four muscles in the push, contrary to the recovery. However, no significant differences were found for the coactivations in the two phases and for the three velocities. These findings denoted the important resistances occasioned by aquatic environment, both in push and recovery phases, necessitating muscle coactivations to stabilise joints

High-intensity interval training improves VO2peak, maximal lactate accumulation, time trial and competition performance in 9–11-year-old swimmers

Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9–11-year-old swimmers on competition performance, 100 and 2,000 m time (T100 m and T2,000 m), VO2peak and rate of maximal lactate accumulation (Lacmax). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P < 0.01; effect size = 0.48) and T2,000 m (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T100 m (P = 0.20). Lacmax increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO2peak increased following both interventions (P < 0.05; effect sizes = 0.46–0.57). The increases in competition performance, T2,000 m, Lacmax and VO2peak following HIIT were achieved in significantly less training time (~2 h/week)

Movement patterns in free water play after swimming lessons with flotation aids

The aim of this study was to investigate the movement patterns of children during free play in a swimming school setting. It was hypothesized that children being taught using flotation vests would be less likely to surface dive, jump, and dive during free play. In this study, 24 participants were observed using a video camera during a 10-minute free play period at the end of a learn-to-swim session. Each subject had undergone 10 lessons either using a flotation vest (n = 11) or without (n = 13). The results showed that the flotation aid group (FLOAT) had significantly fewer surface dives (p = 0.006, using a two sample t-test) compared to the control group (CON) and that FLOAT asked for flotation toys significantly more often than CON (p = 0.03) during free play. No statistically significant differences between groups were observed for breathing, diving, and water entry skills, and the distance moved on land and in water due to low statistical power, but FLOAT participants seemed to be less likely to do vertically-oriented movements. We concluded that children learning to swim using flotation aids had a tendency to move more horizontally during free play and to not choose vertical axis movements (jumping and surface diving) compared to children being taught without the flotation vest

Drag characteristics of competitive swimming children and adults

The aims of this study were to compare drag in swimming children and adults, quantify technique using the technique drag index (TDI), and use the Froude number (Fr) to study whether children or adults reach hull speed at maximal velocity (vmax). Active and passive drag was measured by the perturbation method and a velocity decay method, respectively, including 9 children aged 11.7 ± 0.8 and 13 adults aged 21.4 ± 3.7. The children had significantly lower active (kAD) and passive drag factor (kPD) compared with the adults. TDI (kAD/kPD) could not detect any differences in swimming technique between the two groups, owing to the adults swimming maximally at a higher Fr, increasing the wave drag component, and masking the effect of better technique. The children were found not to reach hull speed at vmax, and their Fr were 0.37 ± 0.01 vs. the adults 0.42 ± 0.01, indicating adults’ larger wave-making component of resistance at vmax compared with children. Fr is proposed as an evaluation tool for competitive swimmers

A proposed framework for developing a plan for research in lifesaving and water safety

In the centers for aquatic research, the infrastructure, methodology, and expertise already exist. What remains is to integrate the needs and interests of lifesaving research into these programs. Especially in physiology and biomechanics, the tools are already in place. The ILS, with two world congresses under its belt, is the ideal agency to foster systematic lifesaving research. This article addresses that issue and recommends a framework for developing a plan for research in lifesaving and water safety