The band squats protocol consists of four sets of four repetitions with two minutes of recovery between sets. Four elastic bands of different resistance will be tested for each participant, and the correct band will be used. During the protocol, subjects will stop at the same depth as a swimming start, with a knee angle between 135 and 145°. All subjects will receive verbal encouragement during the performance in the same way.

The drop jump protocol consists of three sets of five repetitions of jumping after falling from a 45 cm box, with a fifteen-second break to reposition over the box and three minutes of recovery between sets.

A combination of the band squats and the drop jumps

Control Group

The elastic band squat protocol consisted of four sets of four repetitions with two minutes of recovery between sets (estimated total time: 9 minutes). Participants in a standing position should take one of the four elastic resistance bands (GymBeam), anchor it under their feet, and under each shoulder.

Initially, the athlete stands upright on a flat surface or force platform, feet shoulder-width apart, hands on hips (to eliminate arm swing). Without a pause, the athlete performs a quick downward movement (countermovement) by bending the knees and hips, then immediately jumps vertically as high as possible. The athlete lands in an upright position on the same spot, trying to absorb the impact with knees slightly bent. Jump height and flight time is recorded using an optical system, Optojump™ system(Microgate, Bolzano, Italy) connected to a personal computer with dedicated software(OptojumpTM Next software). The system consists of two optical bars, a receiver and a transmitter, positioned 1m apart. The bars identify ground contact time(with a precision of 1ms) and then convert non-contact time into cm. Based on recommendations on optimal jump height (20 to 60cm).

In a second moment, after establishing the best warm-up protocol (from among those proposed) with the best recovery (derived from the CMJ height with the time ratio) for each individual, the 25, 50, and 100 m measurements will be evaluated in the pool. This will take place at a later stage in a 25 m pool. The first part of the warm-up will be the same for all subjects, while the second part will be personalized, based on their Post Activation Performance Enhancement.

The FLIR Foedge thermal imaging camera will be used to capture high-resolution thermal images of the target muscle area under controlled environmental conditions. The thermal imaging camera will be positioned approximately 0.5 meters from the subject's skin surface, with a fixed focal length lens to ensure sharp images. The room will be continuously monitored for temperature and humidity, minimizing external thermal influences. Ambient lighting will be kept low to avoid thermal interference from light sources. The thermal imaging camera will be calibrated before each session, connected to the same smartphone, and images will be captured at a frequency of 30 Hz to monitor temperature changes in real-time before and after muscle activity.