Post-activation potentiation (PAP) refers to the increase in muscle isometric twitch and low frequency tetanic after a conditioning activity. Reliable data on human flutter kick thrust can provide deeper insights into flutter kick mechanisms, which in turn can have a significant impact on the performance of competitive swimmers. Therefore, remains in question if the results from aforementioned studies using simulations, modelling, and preliminary experiments would be representative to those conducted using experimental methods in a more ecological valid setting. However until this date, there is no evidence on flutter kick thrust using experimental methods in a more ecologic valid setting (i.e., unrestricted swimming with swimmers displacing in water). A couple of reports conducted experimental tests but in tethered flutter kicking and a case study of stationary flutter kicking against a wall. Most studies selected computational simulations and analytical modelling. However, the majority of research studies investigated the physiological responses, , kinematics and nonlinear behaviour of flutter kick, with few studies on human flutter kick thrust. Recently, there has been an increasing interest to understand the role of human kicking. Previous research has focused on the thrust produced by upper-limbs during each arm-pull due to its larger contribution to overall swim speed.
BUTTERFLY KICKS EXERCISE FULL
Human kicking contributes to approximately 10–15% of overall speed during full swimming (i.e., arm-pulls and kicks simultaneously). Noteworthy, human kicking resemble to the tail movements of cetaceans. Human locomotion in water depends on the amount of propulsion produced by both upper- and lower-limbs while performing arm-pulls and kicks simultaneously. In comparison with the body of evidence on aquatic animals thrust, the knowledge on human thrust in water is very limited. Since a long time ago, substantial research using different experimental techniques, simulations, and modelling procedures have been conducted on the thrust of aquatic specimens, ,,.
Several aquatic specimens, such as dolphins, are fully adapted to maximize propulsion and minimize drag. Swim acceleration is the net resultant of drag and propulsive forces acting on a body.
Human beings encounter numerous challenges to move in water as compared to aquatic animals. In conclusion, a warm-up that includes PAP sets improves kicking thrust, kinematics and performance. Large and significant differences were noted in speed ( P = 0.01, d = 0.54) and speed fluctuation ( P = 0.02, d = 0.58), which improved by 10% in PAP compared with non-PAP. Kinetics (i.e., peak thrust, mean thrust, and thrust-time integral) and kinematics (i.e., speed, speed fluctuation and kicking frequency) were experimentally collected by an in-house customized system composed of differential pressure sensors, speedo-meter, and underwater camera.
BUTTERFLY KICKS EXERCISE TRIAL
Participants performed a 25 m all-out trial in front-crawl with only flutter kicks eight min after each warm-up. Sixteen male competitive swimmers with 22.13 ± 3.84 years of age were randomly assigned in a crossover manner to undergo a standard warm-up (non-PAP control condition) and a warm-up that included PAP sets (PAP experimental condition) consisting in 2 × 5 repetitions of unloaded countermovement jump. Herein, we analyse by experimental techniques the human kicking thrust and measure the effect of a warm-up routine that includes post-activation potentiation (PAP) sets on front-crawl flutter kick thrust, kinematics, and performance.
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