ESTIMATION OF ONE REPETITION MAXIMUM FOR UNILATERAL LEG PRESS BASED ON THE SKELETAL MUSCLE MASS OF UNILATERAL LOWER EXTREMITY

K. Fukushima^1,2, K. Sue^1,3, K. Oyake⁴, K. Momose⁴

¹Graduate School of Medicine, Science and Technology, Shinshu University, Department of Health Sciences, Matsumoto, Japan, ²Kamijo Memorial Hospital, Department of Rehabilitation, Matsumoto, Japan, ³Kakeyu Misayama Rehabilitation Center, Kakeyu Hospital, Department of Rehabilitation, Ueda, Japan, ⁴Shinshu University, Physical Therapy, Matsumoto, Japan

Background: Resistance training intensity is most often prescribed as a percentage of an individual’s one repetition maximum(1RM). Although the 1RM for single-joint movements can be reportedly estimated by the skeletal muscle mass (SMM) measured by bioelectrical impedance analysis (BIA), it remains unclear whether the 1RM for multi-joint movements can be also estimated by SMM. The estimation of 1RM would be more appropriate to be performed multi-joint movements because SMM is provided separately for each limb using BIA.

Purpose: This study aimed to assess whether the 1RM for unilateral leg press with the dominant leg was estimated from SMM of the dominant lower extremity measured by BIA, even when controlling for potentially confounding variables.

Methods: Thirty-four healthy volunteers (aged 51.6 ± 21.2 years, 20 females, 21.3 ± 2.7 kg/m² of body mass index [BMI]) participated in this study. SMM in the dominant lower extremity was measured using a body composition analyzer (Inbody430; InBody Co., Ltd., South Korea). After measurement of SMM, subjects underwent a unilateral leg press 1RM test performed by the dominant leg, using a plate-loaded angled leg press machine (MB-LPHS, SUPER SPORTS COMPANY Co., Ltd, Japan). The initial position was adopted at a knee flexion angle of 90 degrees and the weight was pushed up until the knees were fully extended. The final weight lifted successfully was recorded as the 1RM. In the bivariate analysis, Pearson’s product-moment correlation coefficient, and the unpaired t-test were used to determine associations of the 1RM for unilateral leg press with SMM of the dominant leg and the confounding variables, based on variable types. The confounders included age, sex, and BMI. Additionally, the stepwise multiple regression analysis was performed to confirm whether the associations between the 1RM for unilateral leg press and variables observed in the bivariate analyses remained significant. Any p values less than 0.05 were considered statistically significant.

Results: The 1RM for unilateral leg press and SMM of the dominant leg were 54.9 ± 26.5 kg and 6.9 ± 1.5 kg, respectively. The 1RM for unilateral leg press was significantly associated with SMM of the dominant leg (r = 0.82, p < 0.001), age (r = -0.47, p = 0.005), and sex (t = 4.99, p < 0.001), but not BMI (r = 0.24, p = 0.176). The stepwise multiple regression analysis revealed that the 1RM for unilateral leg press was estimated from only SMM of the dominant leg, using the following equation: 1RM = -42.1 + 14.0 SMM (R² = 0.68, standard error of estimate = 15.2 kg).

Conclusions: The result of this study suggests that SMM of the dominant leg measured using BIA can independently estimate the 1RM for unilateral leg press.

Implications: The 1RM measurement loads stress on muscles and tendons, consequently increasing the risk of injury. Our findings contribute to the establishment of measurement techniques to safely and simply estimate 1RM for multi-joint movements.

Funding acknowledgements: This study was not supported by any foundation

Keywords:
Strength estimation
Bioelectrical impedance analysis
Skeletal muscle mass

Topics:
Musculoskeletal: lower limb
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: Shinshu University

Committee: Ethics Committee of Shinshu University

Ethics number: 4894