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Effect of Load Positioning on the Kinematics and Kinetics of Weighted Vertical Jumps

Swinton, Paul A.; Stewart, Arthur D.; Lloyd, Ray; Agouris, Ioannis; Keogh, Justin W. L.

Journal of Strength & Conditioning Research: April 2012 - Volume 26 - Issue 4 - p 906–913
doi: 10.1519/JSC.0b013e31822e589e
Original Research

Abstract: Swinton, PA, Stewart, AD, Lloyd, R, Agouris, I, and Keogh, JWL. Effect of load positioning on the kinematics and kinetics of weighted vertical jumps. J Strength Cond Res 26(4): 906–913, 2012—One of the most popular exercises for developing lower-body muscular power is the weighted vertical jump. The present study sought to examine the effect of altering the position of the external load on the kinematics and kinetics of the movement. Twenty-nine resistance-trained rugby union athletes performed maximal effort jumps with 0, 20, 40, and 60% of their squat 1 repetition maximum (1RM) with the load positioned (a) on the posterior aspect of the shoulder using a straight barbell and (b) at arms' length using a hexagonal barbell. Kinematic and kinetic variables were calculated through integration of the vertical ground reaction force data using a forward dynamics approach. Performance of the hexagonal barbell jump resulted in significantly (p < 0.05) greater values for jump height, peak force, peak power, and peak rate of force development compared with the straight barbell jump. Significantly (p < 0.05) greater peak power was produced during the unloaded jump compared with all trials where the external load was positioned on the shoulder. In contrast, significantly (p < 0.05) greater peak power was produced when using the hexagonal barbell combined with a load of 20% 1RM compared with all other conditions investigated. The results suggest that weighted vertical jumps should be performed with the external load positioned at arms' length rather than on the shoulder when attempting to improve lower-body muscular performance.

1School of Health Sciences, Robert Gordon University, Aberdeen, United Kingdom

2Center for Obesity Research and Epidemiology, Robert Gordon University, Aberdeen, United Kingdom

3School of Social and Health Sciences, University of Abertay, Dundee, United Kingdom

4Institute of Sport and Recreation Research New Zealand, School of Sport and Recreation, AUT University, Auckland, New Zealand

Address correspondence to Paul A. Swinton, p.swinton@rgu.ac.uk.

Copyright © 2012 by the National Strength & Conditioning Association.