Methods Participants Forty-four college-aged men and forty-seven college-aged women were included in the study. Some participants had a few months experience in RT, but none had performed it systematically for more than three months. The volunteers were recruited through folders and advertising banners around the University campus. The criteria for entering the study were being at least 18 years of age, not practicing RT for the past 6 months, and being free of clinical problems that could be aggravated by the study procedures. Participants were instructed to not change their habitual nutritional habits during the study and if any relevant nutritional change was detected (e.g., becoming vegetarian, restricting calories, taking nutritional supplements and/or ergogenic aids), the data for that participant was excluded from the analysis. Initially, 50 volunteers were included in each group. An a priori analysis revealed that a sample size of 50 would bring a statistical power of more than 0.9 to detect 10% changes within groups. Data from 9 of them (6 men and 3 women) were excluded from the analysis for failing to meet the inclusion criteria: low attendance (n = 6) and performance of additional RT (n = 3). All women within the study had regular menstrual cycle’s and testing sessions were performed during the luteal phase of each female participant cycle. All participants were notified of the research procedures, requirements, benefits and risks before providing written informed consent. The Institutional Research Ethics Committee granted approval for the study. Peak torque Unilateral elbow flexion peak torque (PT) was measured using 2 sets of 4 maximal concentric repetitions at 60°/s on a Biodex System 3 isokinetic dynamometer (Biodex Medical Inc., Shirley, NY, USA), with 60 s of rest between sets. Calibration of the dynamometer was performed prior to each testing session in accordance with the manufacturer’s specifications. Participants were seated on a Scott Bench (Gervasport, São Paulo, Brazil) with their elbow aligned with the axis of rotation of the dynamometer’s lever arm. The forearm remained in a supinated position throughout the test. Verbal encouragement was given throughout the test. All tests were administered by the same investigator. Baseline test and retest intraclass correlation coefficient (ICC) for elbow flexors PT was 0.96 (0.93–0.98). Resistance training intervention Men and women performed the same RT protocol, including leg press, knee flexion, chest press and lat pulldowns. Before the beginning of the study, participants performed two weeks of familiarization to find loads to be use during training and to acquaint participants with the exercises and the training program. The RT program lasted for 10 weeks and was performed two days a week, with a minimum of 48 h between sessions. All exercises were performed for 3 sets using a load permitting between 8 and 12 repetitions before achieving momentary muscular failure in order to control for intensity of effort (Steele, 2014). If necessary, loads were adjusted from set to set to maintain the designated range of repetitions. Resistance was increased from session to session by the exercise technician when a subject completed ≥12 repetitions before achieving momentary muscular failure while maintaining proper form. The rest periods between sets were two minutes and the participants were instructed to record training logs for each workout day. Training sessions were closely supervised by experienced trainers, since previous research has demonstrated greater gains in supervised vs. unsupervised training (Gentil & Bottaro, 2010). Furthermore, participants had to attend at least 80% of the training sessions to be included in the analysis (Gentil et al., 2013). Statistical analyses All values are reported as mean ± standard deviation. Normality of distribution for outcome measures was tested using the Kolmogorov–Smirnov test. Data meeting assumptions of normality were subjected to a two-way mixed-factor analysis of variance (ANOVA) to examine the effects of both ‘time,’ ‘sex’ and ‘time × sex’ interaction. Where necessary, multiple comparisons with confidence interval adjustment using Bonferroni procedure were used in the post hoc analysis. Statistical significance was set at p ≤ 0.05. Data were analyzed using the Statistical Package for the Social Sciences (SPSS) version 17.0 (SPSS Inc., Chicago, IL).

Results A total of 91 college students participated in the study; mean values for age, weight and height were 22.01 ± 2.74 years, 66.06 ± 12.16 kg and 168.85 ± 9.25 cm, respectively. Table 1 shows the characteristics of the each group. Peak torque values were greater in men than women in pre- (49.35 ± 10.18 vs. 25.09 ± 4.89) and post-tests (55.08 ± 9.95 vs. 28.04 ± 5.52), as shown in Fig. 1 (p < 0.01). Increases in peak torque were significant for both men and women, mean PT 95% CIs [4.36–7.09] and [1.63–4.27], respectively. However, the interaction of sex by time was not significant, suggesting that the alterations in muscle strength were not significant different between sexes (11.61 and 11.76% for men and women, respectively). Cohen’s d effect size for PT changes were 0.57 and 0.56 for men and women, respectively. The statistical power to detect PT changes was 99.4% for women and 98.2% for men. Figure 1: Values and variation in elbow flexor peak torque pre- and post-training period, for men and women. ∗ significantly different from pre-training (p < 0.05). # significantly different from women (p < 0.05). Men Women N 44 47 Age (years) 22.63 ± 2.34 21.62 ± 2.96 Weight (kg) 73.06 ± 10.23 58.29 ± 9.00 Height (cm) 174.7 ± 7.10 163.61 ± 7.53 DOI: 10.7717/peerj.1627/table-1