The Effect of Accentuated Eccentric Loading on Concentric Performance Characteristics of the Jump Shrug Exercise Original Research

Abstract

Introduction: Resistance training loads are often derived from concentric 1RM, despite higher force production capabilities during eccentrics. Accentuated eccentric loading (AEL) allows heavier eccentric loading and may potentiate concentric performance. This study examined the effect of AEL on jump shrug (JS) performance.

Methods: Recreationally trained males (n=15, X̅±SD; age=22.5±2.8 yrs, height=177.0±7.5 cm, body mass=87.6±14.2 kg) performed the JS at varying percentages of body mass (20-120%) with and without AEL. Weight releasers added an additional 20% body mass during the eccentric phase of the AEL condition. All repetitions were performed on a force platform. Peak force, rate of force development (RFD), impulse, and impulse duration were compared between AEL conditions.

Results: Peak force, RFD, and impulse were not different between AEL and non-AEL (p=0.052-0.77). Observed differences were primarily driven by load, with lower peak force during the 20% load, when compared to 60-80% (p=0.004-0.007, g=1.14-1.20). Greater RFD was observed in lighter loads, with 20% greater than 60-120% (p=<0.001-0.003, g=1.28-2.29), 40% greater than 80-120% (p<0.001, g=1.95-3.22), and 60-80% greater than 100-120% (p=<0.001-0.007, g=1.14-1.87). Impulse during 20% was lower than 40-80% (p=<0.001-0.001, g=1.37-1.66), with 80% being greater than 120% (p=0.041, g=0.91). When collapsing across loads, impulse duration was shorter during AEL (p=0.007, g=0.80).

Conclusions: In the current study, AEL minimally influenced JS performance. While shorter impulse duration was observed with AEL, it is unclear if AEL potentiated JS performance or if AEL influenced eccentric displacement. Observed differences were primarily driven by load. Practitioners should understand how load influences JS kinetics.