Calculation of the theoretical maximal force (F0), velocity (V0), and power (Pmax)

We calculated the F₀, V₀, and P_max as basic indicators of the relationship between F and V (F-V relationship) across the six different loads (Fig. 3). We defined the points of intersection of the regression line with the ordinate and transversal axis as F₀, and V₀, respectively, and calculated P_max as described in an earlier study (Jaric, 2015; Samozino et al., 2012; Vandewalle et al., 1987) by using the following equation:

The average values (A) and individual values (B). Force-velocity relationship and parameters derived from each of the two relationships of gymnasts (the closed circle) and judo athletes (the open circle).

P_max = F₀ × V₀ / 4.

In addition to the absolute values, we expressed F₀ and P_max as values relative to CSA_index (F₀/CSA_index and P_max/CSA_index). Furthermore, we adopted the slope of the regression line for the F-V relationship (F-V_slope) as a parameter indicative of predominance of force (or velocity) in the relationship (Samozino et al., 2012). To evaluate the test-retest reliability of ballistic power testing, each subject was tested on 2 separate occasions at the same time of day after an interval at least 3 days. The same warm-up routine and testing protocol were used in both occasions. To determine the test-retest reliability across the two testing sessions, the intraclass correlation coefficient (ICC _1,1) was used. There was no significant difference between the two testing sessions in each of F₀, V₀ and P_max. The ICC_(1,1) for each of the measured parameters ranged from 0.820 to 0.984.