Search Results

Adults with intellectual disabilities (ID) show a greater tendency toward deconditioning and having a sedentary lifestyle than their peers without disabilities. The aim of this study was to characterize sensorimotor deficits through coordination tests and during static and dynamic balance. Eight tasks that involved the integration of hand movements with visual information were used here, as well as the Posture Scale Analyzer system to examine postural stability. During static and dynamic standing tests with the eyes closed, the postural stability of people with ID was accompanied by a small sway rate. In the ID group, the frontal plane movements were significantly larger (p > .05) than the sagittal plane movements. The participants with ID showed a significantly lower score than the control group in all the sensorimotor tests. Our observations on balance and coordination capabilities might have significance for understanding the mechanisms underlying movement dysfunction in adults with ID and offer some new approaches for their possible prevention.

Physical quickness is less in older adults with implications for fall prevention, movement initiation, and activities of daily living. The purpose was to compare control of rapid contractions in young and older adults within two diverse muscle groups: powerful elbow extensors (EE) and dexterous index finger abductors (IFA). Most-rapid force pulses to a variety of levels were recorded and peak force and rate of force development (RFD) were analyzed with linear regression. The resulting slope represents the dependent variable of interest, the RFD-scaling factor (RFD-SF). RFD-SF of EE and IFA strongly correlated both overall (r = .87, p < .01) and separately in young (r = .60, p < .05) and older (r = .77, p < .01) adults. RFD-SF values were different between muscle groups (F _1,28 = 19.1, p < .001) and also less in elderly (F _1,28 = 32.6, p < .001). We conclude that RFD-SF provides a sensitive assessment of muscle quickness that can be used to evaluate neuromuscular function in aging humans.

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.

Several devices (e.g., linear transducers) have been used for predicting resistance training intensity. However, subjective scales, such as rating of perceived exertion (RPE), are proposed as reliable and easier-to-use tools for monitoring intensity during resistance training. Accordingly, different perceptive scales have been presented in previous research for monitoring intensity during resistance training with elastic bands. The aim was to assess the accuracy and reliability of RPE for quantifying the potential maximal repetitions that could be performed at a given RPE (from 2 to 8 of 10) obtained in the first repetition. For this purpose, 13 recreationally active participants (age: 26.33 [6.52] years, body mass index: 24.97 [5.08] kg/m²) were involved in two familiarization and two experimental sessions. In each session, participants randomly performed one set at each intensity of the first repetition from 2/10 to 8/10 until volitional failure in three different exercises (fly, military press, and push–press). An individual grip width of the elastic band was chosen in each set. The number of repetitions and heart rate were assessed. Significance level was set at p < .05. Repetitions decreased when intensity increased (p < .01) and heart rate was higher in the global exercise (i.e., push–press; p < .05), but nonsignificant differences between intensities were reported. The level of experience influenced the number of repetitions performed (p < .05). Intersession reliability was set from good to excellent (range: 0.64–0.91). Therefore, the RPE of the first repetition is a relevant and reliable parameter related to the total number of repetitions performed for each RPE value in trained participants enrolled in elastic bands resistance training.

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; I ² = 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; I ² = 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.

Because of the redundancy of our motor system, movements can be performed in many ways. While multiple motor control strategies can all lead to the desired behavior, they result in different joint and muscle forces. This creates opportunities to explore this redundancy, for example, for pain avoidance or reducing the risk of further injury. To assess the effect of different motor control optimization strategies, a direct measurement of muscle and joint forces is desirable, but problematic for medical and ethical reasons. Computational modeling might provide a solution by calculating approximations of these forces. In this study, we used a full-body computational musculoskeletal model to (a) predict forces measured in knee prostheses during walking and squatting and (b) study the effect of different motor control strategies (i.e., minimizing joint force vs. muscle activation) on the joint load and prediction error. We found that musculoskeletal models can accurately predict knee joint forces with a root mean squared error of <0.5 body weight (BW) in the superior direction and about 0.1 BW in the medial and anterior directions. Generally, minimization of joint forces produced the best predictions. Furthermore, minimizing muscle activation resulted in maximum knee forces of about 4 BW for walking and 2.5 BW for squatting. Minimizing joint forces resulted in maximum knee forces of 2.25 BW and 2.12 BW, that is, a reduction of 44% and 15%, respectively. Thus, changing the muscular coordination strategy can strongly affect knee joint forces. Patients with a knee prosthesis may adapt their neuromuscular activation to reduce joint forces during locomotion.

This study aimed to determine the acute effects of high-intensity forward-backward and low-intensity side-to-side plyometric jumps performed following the warm-up on sprint (5, 10, and 15 m) and change-of-direction (COD) (T-half test and repeated T-half tests) performance in youth volleyball players. After a familiarization week, 30 male volleyball players (age = 12.04 ± 1.03 years) performed three randomized conditions (no-plyometrics, high-intensity plyometrics, and low-intensity plyometrics) in three sessions. In a within-subject design, three sets of six repetitions of forward-backward 30-cm hurdle jumps (high-intensity) and side-to-side 20-cm hurdle jumps (low-intensity) were completed. Sprint and COD were tested after each of the conditions with a 2-min rest. A significant effect of the plyometric condition was observed on sprint (p < .001, ${\mathrm{\eta }}_{\mathrm{p}}^2$ range: .56–.70) and COD (p < .01, ${\mathrm{\eta }}_{\mathrm{p}}^2=.24$ ), but not on repeated COD. More specifically, the high-intensity plyometric condition exhibited significantly better results compared with the low-intensity plyometric (Cohen’s d range: 0.73–1.21) and control conditions (Cohen’s d range: 0.91–2.21). Due to the importance of speed and COD in volleyball, these results suggest that young volleyball players may benefit from high-intensity forward-backward plyometric protocols following the warm-up to improve subsequent performance.