Self-selected vs. Fixed Repetition Duration: Effects on Number of Repetitions and Muscle Activation in Resistance-Trained Men

• Autores: Sanmy R. Nóbrega, Renato Barroso, Carlos Ugrinowitsch, Jean Lucas Fernandes da Costa, Ieda Fernanda Álvarez, Cintia Barcelos, Cleiton Augusto Libardi
• Localización: Journal of strength and conditioning research: the research journal of the NSCA, ISSN 1064-8011, Vol. 32, Nº. 9, 2018, págs. 2419-2424
• Idioma: inglés
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• Resumen

  • The aim of this study was to compare the effects of self-selected and fixed repetition duration (RD) on resistance exercise (RE) volume, muscle activation, and time under tension (TUT) per repetition and per session. Twelve resistance-trained men participated in the study. A randomized cross-over design was used and each participant performed 2 high-intensity RE protocols in a balanced order: (a) 3 sets of RE with self-selected RD (SELF); and (b) 3 sets of RE with fixed RD (2-second concentric and 2-second eccentric [FIX]). Muscle activation was assessed through surface electromyography (EMG) of the vastus lateralis and vastus medialis throughout RE sessions. Overall, RE volume was significantly greater for SELF (p = 0.01), whereas TUT per repetition was significantly greater for FIX (p = 0.0001). No significant differences between protocols were detected for TUT per session. Between-protocol comparisons revealed significantly greater EMG amplitude for SELF compared with FIX at S1 (p = 0.01), S2 (p = 0.03), and S3 (p = 0.03). Both SELF and FIX protocols produced significant increases in EMG amplitude from 25 to 100% (p < 0.001) of set completion. Between-protocol comparisons revealed significantly greater EMG amplitude for SELF compared with FIX at 75% (p = 0.03) and 100% (p = 0.01). In conclusion, self-selected RD resulted in greater volume and muscle activation compared with fixed RD in an RE session.