International journal of sports medicine最新文献

This study aimed to determine whether acute ischemic preconditioning enhances performance in the Jiu-Jitsu anaerobic performance test and its influence on physiological responses in Brazilian Jiu-Jitsu fighters. Seventeen male fighters completed two randomized crossover sessions (ischemic preconditioning and placebo). The ischemic preconditioning protocol consisted of three cycles of 5-minute occlusion at 220 mm Hg followed by 5-minute reperfusion. Performance was assessed using the Jiu-Jitsu anaerobic performance test, while physiological markers included the heart rate, blood lactate, muscle oxygenation, countermovement jump, rating of perceived exertion, and session rating of perceived exertion. Ischemic preconditioning increased total repetitions performed in the Jiu-Jitsu anaerobic performance test (p=0.003) and enhanced muscle oxygenation (p<0.0001). Under the placebo condition, the pre-countermovement jump was higher than the post-countermovement jump (p=0.006). However, under the ischemic preconditioning condition, no significant difference was observed between pre- and post-countermovement jump (p=0.99). No significant differences were observed for heart rate or blood lactate (p>0.05). Additionally, ischemic preconditioning reduced the session rating of perceived exertion compared to the placebo (p=0.04), suggesting a lower session rating of perceived exertion. We concluded that acute ischemic preconditioning induces small but significant improvements in performance and muscle oxygenation, while reducing fatigue and session rating of perceived exertion in Brazilian Jiu-Jitsu athletes, supporting its use as an ergogenic aid in training.

The purpose of the present study was to compare the muscle-to-bone ratio in National Collegiate Athletic Association Division I female athletes (n=387) to those in age-matched controls (n=209). In addition, we examined the muscle-to-bone ratio in low and high impact sports. Total and regional lean soft tissue, fat mass, and bone mineral content were determined by dual X-ray absorptiometry. The muscle-to-bone ratio was calculated by dividing lean soft tissue by bone mineral content. Athletes were categorized by sports: basketball (n=66), cross-country (n=49), diving (n=17), soccer (n=69), softball (n=71), swimming (n=93), and volleyball (n=22). There were significant differences between controls and athletes for total lean soft tissue, fat mass, and bone mineral content. When the total muscle-to-bone ratio in athletes was compared to that in controls, there were no significant differences; however, there were significant differences in the regional muscle-to-bone ratio. Low impact sports (i.e., diving and swimming) had significantly higher total and regional muscle-to-bone ratios than high impact sports (i.e., cross-country, basketball, volleyball, softball, and soccer). The differences identified between sports in total and regional muscle-to-bone ratios may be a result of sport-specific impact and mechanical strain affecting the balance between the muscle and the bone. This study provides insights into how training-induced body composition impacts the balance between the tissues in female athletes.

The objective was to analyze the effect of anodic transcranial direct current stimulation over the the primary motor cortex (M1) on resistance exercise in mentally fatigued individuals. Thirty-five participants performed a Stroop task to induce mental fatigue until they reached 50 mm on the visual analogue scale under three different conditions in a randomized, double-blind, crossover experimental trial. The participants completed a resistance training session with six sets for muscle failure with fixed load (Vload=1 ms^-1) after the Stroop task. During the resistance training session, performance parameters as the maximum number of repetitions, power output, and bar velocity were recorded with a linear encoder. Muscle activation (surface electromyography) and the rating of perceived exertion were also measured throughout the resistance training session. The maximum number of repetitions, mean power output, and mean velocity were higher under the anodic transcranial direct current stimulation condition when compared to the sham and control conditions (p<0.05). Meanwhile, the relative surface electromyographic activity of the vastus lateralis, and the rating of perceived exertion per set were lower under the anodic transcranial direct current stimulation condition when compared to sham and control conditions (p<0.05). This study suggest that anodic transcranial direct current stimulation-induced arousal over the left-M1 brain area thus improving the resistance exercise performances while reducing vastus lateralis surface electromyographic activity and rating of perceived exertion in mentally fatigued subjects.

This study examined the muscle oxygen saturation profiles of core and thigh muscles during cycling and investigated their relationship with gross efficiency across various cycling intensities. Eleven male cyclists and triathletes performed a graded exercise test using a cycle ergometer. Muscle oxygen saturation was measured in the vastus lateralis, biceps femoris long head, erector spinae, and external oblique muscles at each intensity level, along with gross efficiency. The percentage of peak power output at which muscle oxygen saturation began to decrease significantly from the initial load was 60% in the vastus lateralis, 80% in the biceps femoris long head, and 70% in both the erector spinae and external oblique muscles (p<0.05 or p<0.01). In contrast, no significant differences in deoxygenation between muscles were observed at intensities between 60% and 90% of peak power output. At 80% of peak power output, a significant positive correlation was found between gross efficiency and oxygen saturation in the erector spinae (r=0.745, p<0.01). In conclusion, the oxygen saturation profile of core muscles are comparable to those of thigh muscles, and oxygen saturation in the erector spinae may contribute to gross efficiency during high-intensity cycling.

Cardiorespiratory fitness (CRF) is a strong predictor of health and mortality. However, its gold-standard assessment, peak oxygen uptake (V̇O2peak) via cardiopulmonary exercise testing (CPX), is not always feasible in clinical practice. This study aimed to 1) develop exercise-based CRF prediction models for people with vestibular hypofunction (VH) and 2) evaluate the applicability of existing models to this population. Fifty-four adults with unilateral or bilateral VH (56% women) completed maximal CPX for V̇O2peak determination. CRF prediction models were developed using maximal (VHmax) and submaximal (with [VHsub G] and without [VHsub N-G] gas exchange analysis) test characteristics. A 100-fold repeated cross-validation assessed model accuracy. VHmax (r = 0.90, SEE = 3.0), VHsub G (r = 0.86, SEE = 3.6), and VHsub N-G (r = 0.79, SEE = 4.3) showed high predictive accuracy, with minimal bias (<1%). Existing equations misestimated CRF (ES = 0.56-0.68, large). Predictions within ±1 MET were higher for VH models, reaching up to 8-9 out of 10 individual cases. The newly developed VH-specific models offer more accurate, clinically applicable tools for CRF estimation across various clinical scenarios, including settings where maximal testing is not feasible. An automated calculator was developed to support clinical implementation in VH management.

This review sought to identify the impact of COVID-19 infection on the physical performance parameters of soccer players. The systematic review was conducted based on the PRISMA guidelines. The following databases were searched up to the end of October 2024: MEDLINE, Scopus, Mendeley, SPORTDiscus, and Google Scholar. Studies conducted on professional and semi-professional adult male soccer players were considered. For a study to be included, it had to report at least one outcome measure both before and after COVID-19 infection. At the end of the screening procedure, a total of 11 studies met the inclusion criteria. The reviewed studies on V̇O2 max showed mixed results. One study reported a significant (p<0.01) decrease 60 days post-infection, while others found no change or even an increase 1-year post-pandemic. Pulmonary function assessment revealed a significant (p<0.01) increase in respiratory work, whereas one study found no significant changes at rest. GPS (Global Positioning System) -based studies reported a significant (p<0.05) reduction in high-intensity accelerations, decelerations, and high-speed running post-COVID-19, while one study found no differences between infected and non-infected players. Strength, power, and anaerobic power showed no significant decline. These findings should be interpreted with caution due to the small sample sizes and limited number of studies.

This study examined blood flow restriction (BFR) usage and motor unit (MU) behavior of the biceps brachii during a single high-intensity contraction. Twelve resistance-trained males (25±5 y) completed maximal voluntary contractions (MVCs) of the elbow flexors, followed by a 70% MVC with BFR and without BFR (CON). Surface electromyographic (EMG) signals from the 70% MVCs were decomposed to extract MU: recruitment thresholds (RTs), action potential amplitudes (MUAP_AMPS), and mean firing rates (MFRs). EMG amplitude (EMG_RMS) at 70% MVC was normalized (N-EMG_RMS) to MVC EMG_RMS. Paired samples t-tests compared the y-intercepts and slopes of the MUAP_AMP and MFR vs. RT relationships and N-EMG_RMS between treatments. For the MUAP_AMP vs. RT relationships, the y-intercepts were greater (p=0.016) for CON than BFR, whereas the slopes were greater (p=0.024) for BFR than CON. For the MFR vs. RT relationships, the y-intercepts were greater (p=0.039) for BFR than CON, whereas the slopes were more negative (p=0.023) for BFR than CON. N-EMG_RMS was greater (p=0.038) for BFR than CON. BFR accelerated higher-threshold MU recruitment, increased lower-threshold MU firing rates, and increased N-EMG_RMS during a single high-intensity muscle action. BFR may be beneficial for accelerating MU recruitment in populations/scenarios where near-maximal efforts are contraindicated.

The use of aromatase inhibitor (AI) therapy in breast cancer survivors (BCS) has been linked to significant and negative changes in body composition and quality of life. However, the long-term effects (9 months) of combined training (CT=resistance plus aerobic training) following the interruption of CT intervention remain unclear in these variables. Thus, the present study aimed to investigate changes in body composition, bone mineral density, and quality of life during a 1-year follow-up period after 9 months of CT in BCS. Participants were randomized into two groups: CT (n=18) for 9 months, or control group (n=18), with 27 participants (CT=16; control=11) reassessed after the 1-year follow-up. There were significant group×time interactions postintervention, with lower fat mass and fat mass percentage in the CT group. However, after the follow-up period, these values returned to baseline. The CT group shows improvements in quality of life, with higher scores in physical functioning, physical health, social functioning, bodily pain, and vitality compared to the control group. These benefits were maintained after the 1-year follow-up period only in the CT group. This study reinforces the crucial role of consistently maintaining an exercise training program for BCS undergoing AI therapy.

Baseball pitchers commonly suffer shoulder and elbow injuries. Previous research on the relationship between pitch velocity and upper extremity kinetics has been limited to laboratory settings, but recent strides in markerless motion capture have allowed analysis of in-game baseball pitching biomechanics. Therefore, our purpose was to provide normative data of in-game pitching kinetics and assess the relationships between pitch velocity and shoulder and elbow kinetics. Data from 183 college pitchers were included in this retrospective analysis of in-game college baseball games. Multilevel models were used to assess the relationships between pitch velocity and kinetics. Intraclass correlation coefficients were used to assess the intrapitcher relationship between kinetics across multiple outings. The inclusion of random slopes did not meaningfully reduce intrapitcher throwing arm kinetic variance. Additionally, the intrapitcher relationship between throwing arm kinetics and ball velocity did not remain constant across multiple outings. Pitch velocity and in-game throwing arm kinetics did not have a strong intrapitcher relationship, which is different than the results of previous laboratory analyses. The intrapitcher relationship between fastball velocity and throwing arm kinetics does not remain consistent across multiple outings. Additionally, this study provides normative in-game kinetic data for baseball pitching.

A meta-analysis was conducted to compare the effects of high-intensity interval training and sprint interval training on body fat reduction in adults with overweight or obesity. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, eight databases were searched, yielding 10 relevant studies involving 343 participants. Both high-intensity interval training and sprint interval training significantly reduced body fat% (standardized mean difference=- 0.56, 95% confidence interval=(- 0.89,-0.24), and p=0.001 and standardized mean difference=- 0.57, 95% confidence interval=(- 0.85,-0.29), and p=0.000, respectively), fat mass (standardized mean difference=- 0.62, 95% confidence interval=(- 1.01,-0.23), and p=0.002 and standardized mean difference=- 0.51, 95% confidence interval=(- 0.81,-0.21), and p=0.001, respectively), and body mass (standardized mean difference=- 0.43, 95% confidence interval=(- 0.75,-0.11), and p=0.009 and standardized mean difference=- 0.34, 95% confidence interval=(- 0.58,-0.10), and p=0.006, respectively). No significant differences were found between high-intensity interval training and sprint interval training in terms of body composition changes. However, the time spent on sprint interval training was approximately 50% less than that of high-intensity interval training. Subgroup analysis suggested that sprint interval training with shorter work durations (less than 10 s) was more effective in obesity control. In conclusion, both high-intensity interval training and sprint interval training demonstrated similar effectiveness in improving body adiposity. Given its time efficiency and straightforward intensity monitoring, sprint interval training may serve as a viable alternative exercise program for promoting fat reduction in adults with overweight or obesity, provided that it is appropriately designed.