Isokinetics and Exercise Science 29 (2021) 11–20 11 DOI 10.3233/IES-202123 IOS Press Acute effects of muscle failure and training system (traditional vs. rest-pause) in resistance exercise on countermovement jump performance in trained adults Petrus Gantois a,⇤ , Fabiano de Souza Fonseca b , Dalton de Lima-Júnior a , Manoel da Cunha Costa a,c , Bruna Daniella de Vasconcelos Costa d , Edilson Serpeloni Cyrino d and Leonardo de Sousa Fortes a a Associate Graduate Program in Physical Education UPE/UFPB, Federal University of Paraiba, João Pessoa, PB, Brazil b Department of Physical Education, Rural Federal University of Pernambuco, Recife, PE, Brazil c Superior School of Physical Education, University of Pernambuco, Recife, PE, Brazil d Graduate Program of Physical Education, State University of Londrina, Londrina, PR, Brazil Received 9 March 2020 Accepted 19 June 2020 Abstract. BACKGROUND: Traditional and rest-pause systems are commonly used during resistance training. These systems have different rest times between repetitions that might affect neuromuscular status and fatigue level. OBJECTIVE: This study compared the acute effects of traditional and rest-pause resistance exercise done to muscular failure on countermovement jump (CMJ) performance. METHODS: Twenty-nine recreationally strength-trained adults of both sexes aged from 18 to 33 years old performed four experimental resistance exercise sessions (half back-squat exercise) in a randomized order. The experimental conditions were: Traditional system to muscular failure (TR-F; 4 × 15 [15RM]) or non-failure (TR-NF; 5 × 12 [15RM]), and rest-pause system to muscular failure (RP-F; 60 reps with 30 s rest between each failure) or non-failure (RP-NF; 60 reps with 10.2 s rest between each repetition). CMJ height was measured at pre-experiment, Post-15 s, and Post-30 min. Perceived recovery was assessed at pre-experiment, lactate concentration Post-2 min, and rating of perceived exertion Post-30 min. RESULTS: CMJ height decrease occurred at Post-15 s and 30 min for the TR-F, TR-NF, and RP-F sessions (p< 0.05). Interaction effects (p< 0.05) showed exercise to muscle failure (TR-F and RP-F) induced greater neuromuscular decrement at Post-15 s, with RP-F leading to a higher CMJ performance impairment at Post-30 min (p< 0.001). Higher blood lactate concentrations were found following TR-F, TR-NF, and RP-F (p< 0.05) than RP-NF conditions, whereas greater internal training load perception was reported after training to muscular failure (p< 0.05) than non-failure exercise. CONCLUSION: Resistance exercise to muscular failure induced greater CMJ height decrement and internal training load perception than non-failure exercise, with RP-F leading to a higher acute neuromuscular performance impairment. Keywords: Strength exercise, fatigue, neuromuscular performance, training load * Corresponding author: Petrus Gantois, Associate Graduate Pro- gram in Physical Education UPE/UFPB, Federal University of Paraiba, João Pessoa, PB, Brazil. Associate Graduate Program in Physical Education, Department of Physical Education, Health Sci- ences Center, Federal University of Paraiba, Lot. Campus University, João Pessoa, PB, 58051-900, Brazil. E-mail: pgm.gantois@gmail. com. ISSN 0959-3020/21/$35.00 c  2021 – IOS Press. All rights reserved. AUTHOR COPY