Resumen de Effects of Prolonging Eccentric Phase Duration in Parallel Back-Squat Training to Momentary Failure on Muscle Cross-Sectional Area, Squat One Repetition Maximum, and Performance Tests in University Soccer Players

Keisuke Shibata, Kazuki Takizawa, Kazunori Nosaka, Masao Mizuno

• This study aimed to compare 2 squat training programs repeated until momentary failure with different eccentric phase duration (2 seconds vs. 4 seconds) on the changes in muscle cross-sectional area, squat 1 repetition maximum (1RM), squat jump (SJ), and countermovement jump (CMJ) height, agility (T-test), and Yo-Yo intermittent recovery test (YY-IR2). Male university soccer players (19.9 +/- 0.9 years, 172.2 +/- 3.8 cm, 66.1 +/- 6.6 kg) were randomly assigned to one of the 2 groups; CON for 2 seconds and ECC for 4 seconds (C2/E4, n = 11) or CON for 2 seconds and ECC for 2 seconds (C2/E2, n = 11). They performed parallel back-squat exercises twice a week for 6 weeks using 75% 1RM weight to momentary failure in each set for 3 sets with each protocol. Outcome measurements were taken before (Pre) and after 3 (Mid; 1RM, SJ, and CMJ only), and at 6 weeks (Post). One repetition maximum increased more (p < 0.05) for C2/E2 (Pre: 95.9 +/- 12.2 kg, Mid: 108.2 +/- 15.4 kg, Post: 113.6 +/- 14.8 kg) than C2/E4 (95.5 +/- 12.9 kg, 102.7 +/- 15.6 kg, 105.5 +/- 14.9 kg, respectively). Cross-sectional area (50% of the thigh length: 3.5 +/- 2.8%), SJ (6.7 +/- 8.9%) and CMJ height (6.3 +/- 8.6%) increased similarly between C2/E2 and C2/E4, but no significant changes in T-test or YY-IR2 were evident in either group. These results suggest that increasing the ECC phase duration during squat exercises does not produce greater training effects when compared with a shorter ECC phase-duration program with momentary failure.