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Neuromuscular Adaptations After 2 and 4 Weeks of 80% Versus 30% 1 Repetition Maximum Resistance Training to Failure

Jenkins, Nathaniel D.M.1; Housh, Terry J.1; Buckner, Samuel L.2; Bergstrom, Haley C.3; Cochrane, Kristen C.1; Hill, Ethan C.1; Smith, Cory M.1; Schmidt, Richard J.1; Johnson, Glen O.1; Cramer, Joel T.1

The Journal of Strength & Conditioning Research: August 2016 - Volume 30 - Issue 8 - p 2174–2185
doi: 10.1519/JSC.0000000000001308
Original Research

Jenkins, NDM, Housh, TJ, Buckner, SL, Bergstrom, HC, Cochrane, KC, Hill, EC, Smith, CM, Schmidt, RJ, Johnson, GO, and Cramer, JT. Neuromuscular adaptations after 2 and 4 weeks of 80% versus 30% 1 repetition maximum resistance training to failure. J Strength Cond Res 30(8): 2174–2185, 2016—The purpose of this study was to investigate the hypertrophic, strength, and neuromuscular adaptations to 2 and 4 weeks of resistance training at 80 vs. 30% 1 repetition maximum (1RM) in untrained men. Fifteen untrained men (mean ± SD; age = 21.7 ± 2.4 years; weight = 84.7 ± 23.5 kg) were randomly assigned to either a high-load (n = 7) or low-load (n = 8) resistance training group and completed forearm flexion resistance training to failure 3 times per week for 4 weeks. Forearm flexor muscle thickness (MT) and echo intensity, maximal voluntary isometric (MVIC) and 1RM strength, and the electromyographic, mechanomyographic (MMG), and percent voluntary activation (%VA) responses at 10–100% of MVIC were determined at baseline, 2, and 4 weeks of training. The MT increased from baseline (2.9 ± 0.1 cm) to week 2 (3.0 ± 0.1 cm) and to week 4 (3.1 ± 0.1 cm) for the 80 and 30% 1RM groups. MVIC increased from week 2 (121.5 ± 19.1 Nm) to week 4 (138.6 ± 22.1 Nm) and 1RM increased from baseline (16.7 ± 1.6 kg) to weeks 2 and 4 (19.2 ± 1.9 and 20.5 ± 1.8 kg) in the 80% 1RM group only. The MMG amplitude at 80 and 90% MVIC decreased from baseline to week 4, and %VA increased at 20 and 30% MVIC for both groups. Resistance training to failure at 80 vs. 30% 1RM elicited similar muscle hypertrophy, but only 80% 1RM increased muscle strength. However, these disparate strength adaptations were difficult to explain with neuromuscular adaptations because they were subtle and similar for the 80 and 30% 1RM groups.

1Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska;

2Department of Health, Exercise Science, and Recreation Management, University of Mississippi, University, Mississippi; and

3Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky

Address correspondence to Dr. Joel T. Cramer, jcramer@unl.edu.

Copyright © 2016 by the National Strength & Conditioning Association.