Optojump system

The countermovement jump (CMJ) with arms on hips and with a free arm test was used in the current study. The players were informed about the protocol of the tests and had two practice attempts to ensure their understanding of the tests. After the trials, the players performed the CMJ. Each subject had four official CMJ trials, two with their arms on their hips and two with their arms free, with a passive recovery of two minutes in between. Then, the best and average heights were calculated. Vertical jump data were collected using the Optojump system (Microgate, Italy). Jump height data were calculated automatically from flight time by Optojump. In the pre-test, CMJ coefficient of variation (CV) was 4.2% for the SSG group and 3.2% for the HIIT group; in the post-test, it was 3.8% CV for the SSG group and 2.7% CV for the HIIT group. The variability in the CMJ pre-test with free arms was 5.5% CV for the SSG group and 1.8% CV for the HIIT group; in the post-test, it was 3.9% CV for the SSG group and 4.2% for the HIIT group. For statistical analysis, the mean of each assessment moment (pre and post) was used.

Countermovement jump (CMJ) (21 (link)) height was measured using the Optojump system (Optojump photocell system; Microgate, Italy). The girls were instructed to swing their arms during the CMJ and to extend through their knees and ankles during the jump phase. After two familiarization jumps, participants had three attempts, with the best attempt included in the analysis. The intraclass correlation coefficient and coefficient of variation were 0.922 and 2.98 %, respectively.

Forty-five minutes prior to the SSG (PRE) and after a standardized 5 min warm-up [60–70% intensity on a leg cycle ergometer (894E, Monark, Varberg, Sweden) except after the SSG], the participants performed three maximum squat jumps (SJ) with arm swing, with a 30 s recovery between each trial [35 (link)]. All SJs were performed on a customized uniaxial force plate (OptoJump System, Microgate, Bolzano, Italy). The platform uses a strain gauge (Model LC4204-K600; A&D Co. Ltd., Tokyo, Japan) capable of measuring vertical ground reaction force and contains photocells at a distance of 2 mm from the ground, which are constantly communicating. The device detects any interruptions in communication between the bars and calculates their duration. Thus, it was possible to assess the vertical jump. The best SJ based on maximum height was used for further analysis. The SJ test was repeated 15 min after the SSG (POST) and 24 h, 48 h, and 72 h after the SSG.

The test was performed twice, with a 45 s rest interval between attempts, and the highest result was recorded. Participants were required to perform a jump on one leg, with the hands placed on the hips and the opposite leg flexed at a 90° angle at both the hip and knee for CMJ with a left and right leg (CMJL and CMJR, respectively) using the Optojump system (Microgate, Bolzano, Italy). A jump was considered invalid if the technique was incorrect, such as not keeping the hands on the hips or not landing on the same leg. Swinging the flexed leg in the air was permitted, and, upon landing, participants had to maintain balance on the leg they had jumped with for 3 s to ensure a valid attempt. The intraclass correlation coefficient (ICC) was 0.99, and the coefficient of variation (CV) was 3.6%.

Players performed three trials sprinting 30 meters, while time on 10 (10m-sprint), 20 (20m-sprint) and 30 (30m-sprint) meters were taken by a photocells system (Polifemo, Microgate, Bolzano, Italy) which presents high reliability (CV < 2%) [21] (link). Vertical jump performance was evaluated by measuring the flying time during a countermovement jump using the Optojump system (Microgate, Bolzano, Italy); during the jump, the players kept their hands at the hip. A passive recovery of 30 seconds was observed between the three trials. This test was proven to have excellent reliability (CV = 2.2%) [22] (link).