Enhancement of jump performance after a 5-RM squat is associated with postactivation potentiation

Abstract

Weight lifting exercise may induce postactivation potentiation (PAP), thereby enhancing performance of a subsequent biomechanically similar "explosive" movement. However, it has not been shown that weight lifting induces PAP, indicated as potentiation of muscle twitch force. Therefore, the present study tested whether a five repetition maximum squat (5-RM squat) both induced PAP and increased the height of subsequently performed counter-movement jumps (CMJs). Eleven male athletes completed four laboratory sessions on separate days. Two sessions determined whether the 5-RM squat induced PAP: in one, a quadriceps maximal twitch was evoked immediately before and 8min after a set of five CMJs (control); in the other, a twitch was evoked before a CMJ set, which was followed by a 4-min rest, a 5-RM squat, a 4-min rest, and a second twitch. Another two sessions tested the effect of the 5-RM squat on jump performance: in one session, two sets of five CMJs were performed with an 8-min rest between the sets (control); in the second, a 5-RM squat was performed 4min after the first set of CMJs, and then after another 4min the second set of CMJs was performed. Neither twitch torque nor CMJ height changed in the control sessions (P>0.05). In contrast, interpolation of the 5-RM squat increased (P<0.05) both twitch torque (49.5±7.8 to 54.8±11.9Nm; i.e., PAP=10.7%) and CMJ height (48.1±5.6 to 49.5±5.9cm; 2.9%). Since PAP was present at the time when CMJ height increased, it was concluded that PAP may have contributed to the increased CMJ height after a 5-RM squat.