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 = 22.6 years, SD = 2.3; M height = 172.3 cm , SD = 6.8; M weight = 76.2 kg , SD = 9.8; M years of resistance training experience = 4.1, SD = 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 condition (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 (CMJ) test and three sets of HBSE until they reached momentary concentric failure, reporting RPE at the end of each exercise set. Following the CT, participants showed a significantly increased self-perception of MF in relation to the CON condition ( p = 0.01; d = 1.2), but this did not affect their motivation to engage in subsequent tests ( p = 0.99; d = 0.006). Neither the CMJ performances nor the RPE were statistically different between CT and CON conditions ( p = 0.33; d = 0.09 and p = 0.20 ; η2 = 0.20, respectively). TTV was significantly lower in the CT relative to the CON experimental condition (Δ = −15.8%; p = 0.04; η2 = 0.48). Prolonged involvement in a CT was associated with reduced volume on a resistance exercise, though this effect was not associated with changes in CMJ performance or motivation to exercise.
Acute effect of betaine supplementation on muscular endurance during resistance exercise in trained men: a pilot and randomized study
