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Body Mass and Femur Length Are Inversely Related to Repetitions Performed in the Back Squat in Well-Trained Lifters

Cooke, Daniel M.1; Haischer, Michael H.1; Carzoli, Joseph P.1; Bazyler, Caleb D.2; Johnson, Trevor K.1; Varieur, Robert1; Zoeller, Robert F.1; Whitehurst, Michael1; Zourdos, Michael C.1

The Journal of Strength & Conditioning Research: March 2019 - Volume 33 - Issue 3 - p 890–895
doi: 10.1519/JSC.0000000000003021
Research Note
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Cooke, DM, Haischer, MH, Carzoli, JP, Bazyler, CD, Johnson, TK, Varieur, R, Zoeller, RF, Whitehurst, M, and Zourdos, MC. Body mass and femur length are inversely related to repetitions performed in the back squat in well-trained lifters. J Strength Cond Res 33(3): 890–895, 2019—The purpose of this research note was to examine whether relationships existed between anthropometrics (body mass, body fat percentage [BF%], and femur length) and descriptive characteristics (age and sex) with repetitions performed to failure at 70% of 1 repetition maximum (1RM) in the back squat. Fifty-eight subjects (males = 43, females = 15; age: 23 ± 3 years, training age: 5.5 ± 2.5 years, body mass: 80.65 ± 16.34 kg, BF%: 10.98 ± 3.53%, and femur length: 47.1 ± 2.6 cm) completed a 1RM squat followed by one set to failure at 70% of 1RM. Total repetitions performed at 70% of 1RM were 14 ± 4 (range: 6–26). Bivariate correlations showed significant inverse relationships between body mass (r = −0.352, p = 0.003), BF% (r = −0.278, p = 0.014), and femur length (r = −0.265, p = 0.019), with repetitions performed. No significant relationships existed between age and sex (p > 0.05), with repetitions performed. All these variables entered into a standard multivariate regression. The model R 2 was 0.200, and body mass had the largest influence (p = 0.057) because relative importance analysis demonstrated body mass to contribute to 43.87% of the variance (of the R 2) in repetitions performed. No other variable was significant or approached significance (p > 0.05). Our results reveal that body mass, BF%, and femur length all are inversely related to repetitions performed at 70% of 1RM in the back squat.

1Department of Exercise Science and Health Promotion, Muscle Physiology Laboratory, Florida Atlantic University, Boca Raton, Florida; and

2Department of Sport, Exercise, Recreation, and Kinesiology, Center for Excellence and Sport Science and Coach Education, East Tennessee State University, Johnson City, Tennessee

Address correspondence to Dr. Michael C. Zourdos, mzourdos@fau.edu.

Copyright © 2019 by the National Strength & Conditioning Association.