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Effect of Squat Depth and Barbell Load on Relative Muscular Effort in Squatting

Bryanton, Megan A.; Kennedy, Michael D.; Carey, Jason P.; Chiu, Loren Z.F.

Journal of Strength & Conditioning Research: October 2012 - Volume 26 - Issue 10 - p 2820–2828
doi: 10.1519/JSC.0b013e31826791a7
Original Research

Abstract: Bryanton, MA, Kennedy, MD, Carey, JP, and Chiu, LZF. Effect of squat depth and barbell load on relative muscular effort in squatting. J Strength Cond Res 26(10): 2820–2828, 2012—Resistance training is used to develop muscular strength and hypertrophy. Large muscle forces, in relation to the muscle's maximum force–generating ability, are required to elicit these adaptations. Previous biomechanical analyses of multi-joint resistance exercises provide estimates of muscle force but not relative muscular effort (RME). The purpose of this investigation was to determine the RME during the squat exercise. Specifically, the effects of barbell load and squat depth on hip extensor, knee extensor, and ankle plantar flexor RME were examined. Ten strength-trained women performed squats (50–90% 1 repetition maximum) in a motion analysis laboratory to determine hip extensor, knee extensor, and ankle plantar flexor net joint moment (NJM). Maximum isometric strength in relation to joint angle for these muscle groups was also determined. Relative muscular effect was determined as the ratio of NJM to maximum voluntary torque matched for joint angle. Barbell load and squat depth had significant interaction effects on hip extensor, knee extensor, and ankle plantar flexor RME (p < 0.05). Knee extensor RME increased with greater squat depth but not barbell load, whereas the opposite was found for the ankle plantar flexors. Both greater squat depth and barbell load increased hip extensor RME. These data suggest that training for the knee extensors can be performed with low relative intensities but require a deep squat depth. Heavier barbell loads are required to train the hip extensors and ankle plantar flexors. In designing resistance training programs with multi-joint exercises, how external factors influence RME of different muscle groups should be considered to meet training objectives.

1Neuromusculoskeletal Mechanics Research Program, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada

2Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada

3Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada

Address correspondence to Loren Z.F. Chiu, loren.chiu@ualberta.ca.

Copyright © 2012 by the National Strength & Conditioning Association.