Article Mental Fatigue Reduces Training Volume in Resistance Exercise: A Cross-Over and Randomized Study Victor Sabino de Queiros 1 , Matheus Dantas 1 , Leonardo de Sousa Fortes 2 , Luiz Felipe da Silva 1 , Gilson Mendes da Silva 3 , Paulo Moreira Silva Dantas 1 , and Breno Guilherme de Ara ujo Tino ˆ co Cabral 1 Abstract The present study aimed to determine the effect of mental fatigue (MF) on total training volume (TTV; number of repetitions x number of sets x load) and on ratings of perceived exertion (RPE; Borg, 1982) in the half-back squat exercise (HBSE). Nine male subjects (M age ¼ 22.6 years, SD ¼ 2.3; M height ¼ 172.3 cm, SD ¼ 6.8; M weight ¼ 76.2 kg, SD ¼ 9.8; M years of resistance training experience ¼ 4.1, SD ¼ 2.3 years) recruited from a university population were study participants in this participant-blind cross-over and randomized study. Participants underwent either the Stroop task – a highly demanding cognitive task (CT) – or a control con- dition (CON) in which they viewed a documentary exhibition for 30 minutes. Perception of MF and motivation were assessed after treatments using a visual analog scale of 100 mm. Participants then engaged in a countermovement jump 1 Department of Physical Education, Federal University of Rio Grande do Norte, Natal-RN, Brazil 2 Department of Physical Education, Federal University of Para  ıba, Jo~ ao Pessoa-PB, Brazil 3 Department of Physical Education, Maur  ıcio de Nassau University Center, Campina Grande-PB, Brazil Corresponding Author: Victor Sabino de Queiros; Department of Physical Education, Federal University of Rio Grande do Norte, University Campus, Lagoa Nova – Natal (RN), Brazil. Email: victor.s14@hotmail.com Perceptual and Motor Skills 0(0) 1–15 ! The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0031512520958935 journals.sagepub.com/home/pms