Comparative Effects of Eccentric-driven Exercise on Measures of Muscle Function When Combined With Aquatic Plyometric Exercise

Maximal eccentric strength

时间窗: 7 weeks

Eccentric muscle strength will be assessed via Eccentron (BTE Technologies, Inc., USA), a seated isokinetic dynamometer. . The pedals will move toward the participant in an alternating motion, so that each leg will work isolaterally in a repetitive manner. There will be a total of 12 maximal effort repetitions, six for each leg. For testing purposes, the speed of this motion will be set at 23 cycles per minute, which is defined as a moderate speed (Gordon et al., 2019).

Maximal isometric strength

时间窗: 7 weeks

Participants will be tested on a custom-made isometric mid-thigh pull (IMTP) device. This device consists of a force plate set onto an aluminum plate to which a bar is attached via chains, which are adjustable for height. The subject will be fitted with an over-the-shoulder vest which will be secured to straps fixed to the force plate. The straps will be adjusted so that the participant's knee angle is set within a range of 125-145°, and the hip angle in a range of 140-150°, as has been suggested to be optimal (Comfort et al., 2019). Participants will be instructed to stand on the plate with feet shoulder width apart, and then to move to a point where the slack is all out of the straps. To initiate the pull, participants will be instructed to drive their feet through the floor as hard and as fast as they can, while keeping their feet and upper body in position, starting on the signal, and not performing a countermovement prior to the pull.

Depth jump

时间窗: 7 weeks

Participants will perform three maximal-effort depth jumps from a height of 0.4 meters onto a force plate. Participants will be instructed to step straight off of the box without lowering themselves prior to falling, then to land and quickly jump as high as they can with minimal ground contact time. A successful jump attempt requires landing on the force plate with both feet both from the drop as well as from the rebound jump. A 1-minute rest period will be provided between each jump attempt.

40-m sprint

时间窗: 7 weeks

Participants will perform three maximal-effort 40-m sprints on a hard track surface in accordance with procedures outlined by (Gordon et al., 2019). Sprint time will be measured by timing gates (Dashr Motion Performance Systems, Dashr LLC, Lincoln, Nebr., USA) positioned at the start and end points of the run distance. Participants will be instructed to start in a 3-point stance with their feet staggered and one hand on the ground. For the three point stance, participants will be instructed to place the front of their lead foot on a line 30 cm behind the start line, and to place the opposite hand of the lead foot on the starting line (Rimmer \& Sleivert, 2000). The sprint will be started with the use of a verbal command and participants will be instructed to run through a line 10 meters past the second timing gate to ensure they give full effort throughout the entire measured distance. Three trials of sprints will be performed, with a rest period of two minutes between each trial.

Countermovement jump

时间窗: 7 weeks

Participants will perform three maximal counter movement vertical jumps on a force platform. Participants will be instructed to stand on the platform with their feet shoulder width apart with their hands on their hips. Participants will be instructed to quickly lower themselves to a comfortable depth then immediately jump as high as possible while landing with their legs relatively straight (Crane et al., 2020). A successful countermovement jump attempt will be counted if the participant lands on the platform with both feet and does not take a step before jumping (Palmer et al., 2014). A 1-minute rest period will be provided between each jump attempt. Participants will be asked to perform three practice jumps with their hands placed on hips. Following the completion of practice jumps, participants will perform 3 trials of countermovement jumping on land and 3 trials while immersed in water at waist-depth.