Abstract
This study aimed to evaluate the degree to which transcutaneous electrical stimulation (ES) enhanced recovery following a simulated water rescue. Twenty-six lifeguards participated in this study. The rescue consisted of swimming 100 m with fins and rescue-tube: 50 m swim approach and 50 m tow-in a simulated victim. Blood lactate clearance, rated perceived effort (RPE), and muscle contractile properties were evaluated at baseline, after the water rescue, and after ES or passive-recovery control condition (PR) protocol. Tensiomiography, RPE, and blood lactate basal levels indicated equivalence between both groups. There was no change in tensiomiography from pre to post-recovery and no difference between recovery protocols. Overall-RPE, legs-RPE and arms-RPE after ES (mean ± SD; 2.7 ± 1.53, 2.65 ± 1.66, and 2.30 ± 1.84, respectively) were moderately lower than after PR (3.57 ± 2.4, 3.71 ± 2.43, and 3.29 ± 1.79, respectively) (p = 0.016, p = 0.010, p = 0.028, respectively). There was a significantly lower blood lactate level after recovery in ES than in PR (mean ± SD; 4.77 ± 1.86 mmol·L−1 vs. 6.27 ± 3.69 mmol·L−1; p = 0.045). Low-frequency ES immediately after a water rescue is an effective recovery strategy to clear out blood lactate concentration.
Highlights
Lifeguards require a high level of physical conditioning to respond to the physiological demands of a water rescue [1]
A quasi-experimental cross-over study design was used to test the effectiveness of one recovery method, low-frequency electrical stimulation (ES), compared with seated resting, as a typical passive recovery (PR) strategy, on the blood lactate clearance, perceived effort, and muscle contractile properties after performing a water rescue (Figure 1)
The paired t-test revealed no significant difference between the two trials, with a small effect size for all variables
Summary
Lifeguards require a high level of physical conditioning to respond to the physiological demands of a water rescue [1]. Drowning is a global health problem, which in 2017 caused 295,210 drowning deaths [2], a number that would be much higher without lifeguard prevention and rescues. Within seconds or minutes [3], so the intensity of lifeguards’ water rescues is very high, with lactate production of over 10 millimoles [4,5] and great physiological and muscular fatigue [6]. Considering a lifeguard can have more than one rescue per day [7], the physiological and metabolic. Res. Public Health 2020, 17, 5854; doi:10.3390/ijerph17165854 www.mdpi.com/journal/ijerph
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