Comparison of Pre-stretch and Reactive Strength Between Men and Women During Bench Press

Abstract

Pre-stretch augmentation (PAI) and reactive strength (RSI) indices have been used to assess the stretch-shortening cycle (SSC) contribution to vertical jumping. SSC activation is also a part of many upper extremity (UE) activities, however quantification of SCC contribution to UE function largely remains unknown. Furthermore, based on differences in UE muscle-tendon properties, the SSC effect is likely different between men and women PURPOSE: To compare UE PAI and RSI indices between men and women. METHODS: 20 men (26±2.4 yrs) and 17 women (21.4±2.6 yrs) with >6 months of UE resistance training completed 3 bench press trials using 2 styles, pure concentric (PC) and rebound (RB) (no pause between eccentric the concentric phases), using 75% of their one repetition maximum. Participants were instructed to complete the concentric phase as quickly as possible. Concentric phase vertical average force (AF) and power (AP) were computed from barbell kinematic data and used to calculate PAI [(RB-PC)/PC*100] and RSI (RB-PC). Independent t tests, adjusted for unequal variances, were conducted to compare indexes between sexes RESULTS: Except for one man and one woman, participants demonstrated greater AF and AP during the RB bench press compared to PC bench press. Men (.49±.38) had significantly higher (P=.004, d=.75) AF PAI than the women (.27±.17). There was no significant (P=.068, d=.64) sex difference for AP PAI. Men (AF:3.9±2.9, AP:129.0±56.7) demonstrated significantly higher RSI for both AF (P<.001, d=1.5) and AP (P<.001, d=2.3) than women (AF:.76±.54, AP: 29.6±18.1). CONCLUSIONS: Except for two participants, as expected, preceding the concentric phase with SSC resulted in greater average force and power production. With the exception of AP PAI, SSC augmentation was greater for the men. Consistent with the RSI reflecting the AP/AF difference between RB and PC bench press styles, the sex comparison effects sizes were larger for the RSI than the PAI, which expresses the difference relative to the PC. Further research is needed to determine the extent to which UE muscle-tendon properties explain the sex differences identified.