Muscle activation during three sets to failure at 80 vs. 30 % 1RM resistance exercise
- 2.1k Downloads
The purpose of this study was to investigate electromyographic amplitude (EMG AMP), EMG mean power frequency (MPF), exercise volume (VOL), total work and muscle activation (iEMG), and time under concentric load (TUCL) during, and muscle cross-sectional area (mCSA) before and after 3 sets to failure at 80 vs. 30 % 1RM resistance exercise.
Nine men (mean ± SD, age 21.0 ± 2.4 years, resistance training week−1 6.0 ± 3.7 h) and 9 women (age 22.8 ± 3.8 years, resistance training week−1 3.4 ± 3.5 h) completed 1RM testing, followed by 2 experimental sessions during which they completed 3 sets to failure of leg extension exercise at 80 or 30 % 1RM. EMG signals were collected to quantify EMG AMP and MPF during the initial, middle, and last repetition of each set. Ultrasound was used to assess mCSA pre- and post-exercise, and VOL, total work, iEMG, and TUCL were calculated.
EMG AMP remained greater at 80 % than 30 % 1RM across all reps and sets, despite increasing 74 and 147 % across reps at 80 and 30 % 1RM, respectively. EMG MPF decreased across reps at 80 and 30 % 1RM, but decreased more and was lower for the last reps at 30 than 80 % 1RM (71.6 vs. 78.1 % MVIC). mCSA increased more from pre- to post-exercise for 30 % (20.2–24.1 cm2) than 80 % 1RM (20.3–22.8 cm2). VOL, total work, iEMG and TUCL were greater for 30 % than 80 % 1RM.
Muscle activation was greater at 80 % 1RM. However, differences in volume, metabolic byproduct accumulation, and muscle swelling may help explain the unexpected adaptations in hypertrophy vs. strength observed in previous studies.
KeywordsElectromyography Skeletal muscle Muscle fatigue Muscle size Resistance training intensity Exercise volume
One repetition maximum
Analysis of variance
- EMG AMP
- EMG MPF
Electromyographic mean power frequency
Total integrated electromyographic amplitude
Muscle cross-sectional area
Maximal voluntary isometric contraction
Time under concentric load
The authors would like to thank Noelle M. Yeo and Jessie M. Miller for their help with data collection. This study was supported in part by the University of Nebraska Agricultural Research Division with funds provided through the Hatch Act (Agency: United States Department of Agriculture, National Institute of Food and Agriculture; Accession No.: 1000080; Project No.: NEB-36-078).
Conflict of interest
The authors have no perceived conflicts of interest to declare.
- Basmajian JV, De Luca CJ (1985) Muscles alive : their functions revealed by electromyography, 5th edn. Williams & Wilkins, BaltimoreGoogle Scholar
- Beck TW, Housh TJ (2008) Use of electromyography in studying human movement. In: Hong Y, Bartlett R (eds) Routledge handbook of biomechanics and human movement. Routledge, New York, pp 214–230Google Scholar
- Brody LR, Pollock MT, Roy SH, De Luca CJ, Celli B (1991) pH-induced effects on median frequency and conduction velocity of the myoelectric signal. J Appl Physiol (1985) 71:1878–1885Google Scholar
- Carpinelli RN (2008) The size principle and a critical analysis of the unsubstantiated heavier-is-better recommendation for resistance training. J Exerc Sci Fitness 6:67–86Google Scholar
- Fukunaga T, Ichinose Y, Ito M, Kawakami Y, Fukashiro S (1997) Determination of fascicle length and pennation in a contracting human muscle in vivo. J Appl Physiol (1985) 82:354–358Google Scholar
- Garber CE et al (2011) American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc 43:1334–1359. doi: 10.1249/MSS.0b013e318213fefb CrossRefPubMedGoogle Scholar
- Hermens HJ et al (1999) SENIAM 8: European recommendations for surface electromyography. Roessngh Research and Development, The NetherlandsGoogle Scholar
- NSCA (2008) Essentials of strength training and conditioning, 3rd edn. Human Kinetics, ChampaignGoogle Scholar
- Terzis G, Spengos K, Mascher H, Georgiadis G, Manta P, Blomstrand E (2010) The degree of p70 S6k and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume. Eur J Appl Physiol 110:835–843. doi: 10.1007/s00421-010-1527-2 CrossRefPubMedGoogle Scholar