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The Acute Effects of Moderately Loaded Concentric-Only Quarter Squats on Vertical Jump Performance

Crum, Aaron J.; Kawamori, Naoki; Stone, Michael H.; Haff, G. Gregory

The Journal of Strength & Conditioning Research: April 2012 - Volume 26 - Issue 4 - p 914–925
doi: 10.1519/JSC.0b013e318248d79c
Original Research

Crum, AJ, Kawamori, N, Stone, MH, and Haff, GG. The acute effects of moderately loaded concentric-only quarter squats on vertical jump performance. J Strength Cond Res 26(4): 914–925, 2012—Limited research exists examining the effect of moderately loaded conditioning activities that are employed as part of a strength-power potentiating complex (SPPC). Additionally, no studies to date have explored the effects of using a concentric-only quarter back squat protocol as part of an SPPC. Therefore, the purpose of this study was to examine the effects of a moderately loaded (50–65% of 1RM) concentric-only quarter back squat protocol on the occurrence of potentiation effects at various time points. Twenty men who could quarter back squat a minimum of 2.4 times their body mass (3.7 ± 0.7 kg·per body mass) participated in this investigation. All subjects participated in 3 conditions: control (CT), a 50% of 1RM trial (50POT), and a 65% of 1RM trial (65POT). One minute before each condition, a maximal countermovement vertical jump (CMJ) was performed. One minute later, the subject performed 1 of 3 conditions: CT condition, 50POT, or 65POT, followed by vertical jumps at 0.5, 3, 5, 10, and 15 minutes after conditioning activity. A force plate was used to quantify displacement, peak power output, peak force, and the rate of force development for each CMJ. There were no significant differences (p > 0.05) in any of the performance measures quantified during the CMJ trials when comparing the CT, 50POT, and 65POT treatment conditions. However, 48% of the subjects demonstrated some degree of potentiation at the 30 seconds after completing the 65POT trial, but this percent increase was not statistically significant. From a practical perspective, if the goal of the SPPC is to create a maximization of the potentiation effect, moderately loaded activities may not be the best alternative.

1Department of Kinesiology, Midwestern State University, Wichita Falls, Texas

2Japan Institute of Sports Sciences, Tokyo, Japan

3Department of Kinesiology, Leisure and Sport Sciences, Center of Excellence for Sport Science and Coach Education, East Tennessee State University, Johnson City, Tennessee

4School of Exercise, Biomedical, and Health Sciences, Edith Cowan University, Joondalup, Australia.

Address correspondence to Dr. G. Gregory Haff,

Copyright © 2012 by the National Strength & Conditioning Association.