Thrust-back: a new technique to augment gains in power and power endurance

Abstract

Background: Speed-oriented power training with light intensities permits rapid acceleration at the beginning of each concentric phase, but necessitates significant deceleration in the later concentric phase to halt the motion. Force exertion and speed of muscle contraction are therefore delimited. To improve the concentric effort, ballistic actions using a Smith machine have been recommended (bench press throws and squat jumps etc). Typical Smith machines however allow vertical pushing exercises only. Hence, a new technique that mimics ballistic actions needs to be developed. In this study, an alternative technique, described as “thrust-back” has been introduced, where the spotter’s hands, rather than the lifter, halt the concentric motion. The effectiveness of thrust-back applied during fast bench press training on concentric velocity as well as gains in 1RM strength, power and power endurance was examined. Methods: Seventeen university students (12 males and 5 females), who abstained from chest exercises for 3~36 months, performed 15 repetitions of fast bench press at 30% 1RM with and without (control) thrust-back. Peak and mean concentric bar velocities were calculated using a string potentiometer. Subjects were then divided into two groups to undergo 8 weeks (16 sessions) of fast bench press training at 30% 1RM (15 repetitions×4~6sets) with or without thrust-back. One-RM, power and power endurance were evaluated before and after the training. Power and power endurance were estimated via the bar flight distances achieved during 20 repetitions of bench press throws at 30% 1RM on a Smith machine. Results: Thrust-back produced greater peak (up to +13%, P<0.001) and mean (up to +10%, P=0.026) concentric velocities than the control. After 8 weeks of implementation, the thrust-back training resulted in similar 1RM improvement to that of the control (+12.9 vs. +6.4%, P<0.001), but yielded greater improvements in the bar flight distances than the control (+13~37% vs. +4~13%, P=0.027). Moreover, the decline in the bar flight distances across 20 repetitions of bench press throws was attenuated after the thrust-back training (P=0.012), while the declining patter remained similar after the control training. Discussion: The augmented concentric velocity (and effort) via thrust-back technique did not magnify 1RM strength gain compared to the control training, however was successfully translated into greater gains in power and power endurance. When Smith machines are not available or not suited to perform the intended exercises, then thrust-back technique may become an alternative strategy since it can be applied to various exercise types. The authors declare no conflict of interest.