The purpose of the present systematic review and meta-analysis was to explore the effects of mental fatigue on upper and lower body strength endurance. Searches for studies were performed in the PubMed/MEDLINE and Web of Science databases. We included studies that compared the effects of a demanding cognitive task (set to induce mental fatigue) with a control condition on strength endurance in dynamic resistance exercise (i.e., expressed as the number of performed repetitions at a given load). The data reported in the included studies were pooled in a random-effects meta-analysis of standardized mean differences. Seven studies were included in the review. We found that mental fatigue significantly reduced the number of performed repetitions for upper body exercises (standardized mean difference: −0.41; 95% confidence interval [−0.70, −0.12]; p = .006; I² = 0%). Mental fatigue also significantly reduced the number of performed repetitions in the analysis for lower body exercises (standardized mean difference: −0.39; 95% confidence interval [−0.75, −0.04]; p = .03; I² = 0%). Our results showed that performing a demanding cognitive task—which induces mental fatigue—impairs strength endurance performance. Collectively, our findings suggest that exposure to cognitive tasks that may induce mental fatigue should be minimized before strength endurance-based resistance exercise sessions.

Objectives: This study aimed to explore the effects of four days of Rhodiola Rosea (RR) supplementation on bench-press and bench-pull exercises under resting or mental fatigue conditions in young healthy individuals. Methods: Eighteen participants (seven women) visited the laboratory on five occasions separated by 7 days—one preliminary session and four experimental sessions. In the preliminary session, participants were familiarised with the Stroop and Multiple Object Tracking tests, after which their one-repetition maximum loads for bench presses and bench pulls were determined. The four experimental sessions had the same protocol, differing only in the supplement (RR or placebo) and mental task conditions (Stroop test or control video). Participants were assigned randomly and counterbalanced to each experimental condition: (I) RR and Stroop test, (II) RR and control video, (III) placebo and Stroop test, and (IV) placebo and control video. Results: The main findings indicate that RR supplementation has trivial-to-small effects in terms of mental fatigue, visuo-cognitive processing, or perceived exertion. However, RR was significantly superior to placebo on strength performance in the control video condition during some sets, as it increased the number of repetitions performed in the bench press and the fastest velocity in the bench pull. Out of 52 comparisons, 17 small effect sizes were observed, with 14 favouring RR and 3 favouring placebo, with the remaining differences being trivial. Conclusions: These results suggest that short-term RR supplementation is safe and provides its main ergogenic effects on physical performance rather than in visuo-cognitive or mental outcomes.

The aim of this study was to explore the effects of mental fatigue from smartphone use and Stroop task on bench press force–velocity (F-V) profile, one-repetition maximum (1RM), and countermovement jump (CMJ) performance. Twenty-five trained subjects (age = 25.8 ± 5.7 years) completed three sessions separated by 1 week following a randomized double-blinded crossover design. Each session consisted of F-V relationship, 1RM, and CMJ measurements after performing 30 min of control, social media, or Stroop task. Perceived mental fatigue and motivation were recorded. Mental fatigue, motivation, CMJ height, bench press 1RM, and F-V profile variables (maximal force, maximal velocity, and maximal power) were compared between interventions. Significant differences were found for mental fatigue between interventions (p ≤ .001). Both ST (p ≤ .001) and SM (p = .007) induced higher mental fatigue than control. However, no significant differences between interventions were observed for any other variable (p = .056–.723). The magnitude of the differences between interventions ranged from negligible to small (effect sizes ≤ 0.24). These results suggest that although both ST and SM were effective to induce mental fatigue, neither ST nor SM affected CMJ performance, bench press 1RM, or any variable of the F-V profile compared with the control task.

(1) Background: Non-communicable diseases (NCD) are an important concern for public health because of their high rates of morbidity and mortality. A prevalent lifestyle-linked NCD is type 2 diabetes mellitus (T2D). Recently, molecular biomarkers secreted by adipocytes, called adipokines, have been linked with T2D and muscle function disturbances. However, the effects of resistance training (RT) interventions on adipokine levels in patients with T2D have not been systematically studied. (2) Methods: The PRISMA guidelines were followed. Searches for the studies were performed in the PubMed/MEDLINE and Web of Science electronic databases. Eligibility criteria included: (i) participants with T2D; (ii) RT interventions; (iii) randomized controlled trials; and (iv) measurement of serum adipokines. The PEDro scale was used to assess the methodological quality of the selected studies. Significant differences (p ≤ 0.05) and effect size were screened for each variable. (3) Results: Of the initial 2166 records, database search extraction yielded 14 studies to be included. The methodological quality of the included data was high (median PEDro score of 6.5). Analyzed adipokines in the included studies were leptin, adiponectin, visfatin, apelin, resistin, retinol-binding protein 4 (RBP4), vaspin, chemerin, and omentin. RT interventions (6–52 weeks; minimal effective duration >12 weeks) exert a meaningful effect on serum adipokine, (e.g., leptin) levels in T2D patients. (4) Conclusions: RT may be an alternative, but not an optimal, option in adipokine disruptions in T2D. Combined (i.e., aerobic and RT) long-term training may be considered the optimal intervention for treating adipokine level disturbances.