Decrease of Muscle Performance After Two Different Load Protocols in Well-Trained Men

Abstract

To study muscle damage recovery, firstly muscle damage has to be induced by an exercise. A specific drop jumps protocol has been largely used in previous studies. However, all participants studied were untrained. PURPOSE: To assess muscle strength, muscle power and muscle swelling after two different load drop jump protocols in well-trained athletes. METHODS: Eighteen strength and/or power-trained male athletes (4.31±2.75 years of training experience) were randomly assigned into one of two groups. DJ100 consisted in 5 sets of 20 drop jumps from a 60-cm box with 2-minute rest interval (n=9, 23.00±2.74 years). DJ140 consisted in seven sets of 20 drop jumps also (n=9, 22.89±3.37 years). Volunteers performed a maximally explosive vertical jump. Both groups performed the assessment of indirectly markers of muscle damage before and immediately after exercise protocol. Muscle thickness of knee extensors was measured using B-mode ultrasound. Maximal isometric muscle strength (PT) was measured by 2 sets of 4 seconds maximal isometric knee extension at 60°. For vertical jump, the athletes performed three countermovement jumps as high as possible, with one-minute rest between jumps. After normal distribution confirmed by Shapiro-Wilk tests, independent samples T-tests were used to compare the magnitude of changes of muscle thickness, isometric strength and vertical jump between groups. A p-value of ≤ 0.05 was adopted. RESULTS: There was no significant difference (p>0.05) in sample’s baseline characteristics between groups. There was no significant difference in the increase of muscle thickness (DJ100: 6.47 ± 1.67 (16.50%) vs. DJ140: 7.51 ± 2.31 mm (17.82%); p = 0.286). The decrease of isometric strength was significantly greater in DJ140 than DJ100 (DJ100: 34.24 ± 22.30 (11.20%) vs. DJ140: 67.06 ± 38.79 N.m (22.41%); p = 0.043; ES = 1.037). The decrease of vertical jump was also significantly greater in DJ140 than in DJ100 (DJ100: 0.48 ± 2.88 (0.95%) vs. DJ140: 7.72 ± 7.44 cm (17.42%); p = 0.015; ES = 1.283). CONCLUSIONS: The main finding of this study was that an exercise protocol composed by 100 drop jumps did not decrease lower limb muscle power in well-trained athletes. Furthermore, 140 drop jumps induced a decrease in muscle performance greater than 100 drop jumps in well-trained athletes.