Efeito da duração do intervalo entre saltos verticais: relação entre impulso concêntrico e duração do exercício

Abstract

The critical power model has been applied to many sports which are continuously (e.g., run and swim) and intermittently (e.g., run) performed. However, there is no study applying critical power model to intermittent vertical jump exercise. Then, this study aimed to verify whether critical power model fits to countermovement jumps (CMJs) performed with different passive rest period lengths between jumps. Ten males performed four experimental sessions across different days. The 1st, 2nd and 3rd sessions (S1, S2 e S3) were performed in order to determine the critical interval. They consisted of performing intermittent CMJs (likewise volleyball block) on the force platform, manipulating the rest period lengths (from 4 to 7 s), until exhaustion. Three consecutive failures to reach the target height (i.e., 95% maximal jump height) were considered exhaustion. The concentric impulse, determined through vertical ground reaction force integration with time, was estimated for each CMJ. Thus, the sum of concentric impulses was determined for every experimental session. It was assumed that such a sum represented the total external work to elevate the center of mass during the CMJs. Then, the linear work-time mathematical equation was used to estimate the critical interval. It was hypothesized that critical interval represents the smallest rest period length between CMJs allowing long-term exercise. In order to test such hypothesis, in the 4th experimental session (SCI), the subjects performed CMJs until exhaustion using the critical interval. During all experimental sessions, the number of CMJs and exercise duration (time from the first to last jump) were determined. The number of CMJs performed during S2 (70 ± 28 jumps), S3 (105 ± 28 jumps) e SCI (171 ± 51 jumps) were significantly higher than S1 (42 ± 14 jumps). In addition, the number of CMJs performed during S3 and SCI were significantly higher than S2, while SCI was higher than S3. Regarding exercise duration (S1=171 ± 52 s; S2=346 ± 117 s; S3=610 ± 129 s and SCI=1304 ± 339 s) and sum of concentric impulses (S1=10,297 ± 3,508 N•s; S2=17,077 ± 6,386 N•s; S3=25,883 ± 7,188 N•s and SCI=45,377 ± 14,608 N•s) variables, the significant differences were similar to the responses obtained by number of CMJs for every experimental sessions. Moreover, there was high coefficient of determination (R2 = 0.99 ± 0.01) between the sum of concentric impulses and exercise durations used to estimate the critical interval (7.4 ± 1.3 s). Therefore, the critical power model can be applied to estimate the critical interval in vertical jump exercise, being critical interval the smallest rest period length between CMJs which allows long-term exercise.