Journal of Sport and Health Science最新文献

Background: Deficits in quadriceps strength of the injured leg have been observed in patients following anterior cruciate ligament (ACL) reconstructions and may contribute to ACL re-injury risk. Single-leg forward hopping is a widely used task for assessing knee function in patients following ACL reconstructions as it has been shown not to be particularly challenging to the knee. This study aimed to quantify the effect of decreased quadriceps strength induced by a fatigue protocol on hopping performance and lower limb mechanics in single-leg forward, vertical, and backward hopping.

Methods: Thirty-four injury-free participants performed single-leg forward, vertical, and backward hopping on both legs pre- and post-fatigue, with 1 leg experiencing a fatigue protocol. Peak moments, power, and work of hip, knee, and ankle joints were quantified during the jumping phase. Hopping performance and bilateral asymmetries in performance were assessed.

Results: Single-leg backward hopping demonstrated the greatest knee moments, power, and work compared to forward and vertical hopping, regardless of leg and fatigue. Fatigue protocol resulted in significantly less knee moments, power, and work, and decreased performance of the fatigued leg among all tasks. Bilateral symmetries in hopping performance decreased in post-fatigue, with the greatest decrease in backward hopping.

Conclusion: The greater sensitivity of the backward hopping to detect quadriceps fatigue suggests it may act as a better or at least an additional metric to evaluate quadriceps strength deficits. The findings may contribute to the development of a clinically applicable and valid strength assessment to monitor the rehabilitation progress in patients following ACL reconstructions.

Background: Quantifying the potential benefits of advanced footwear technology (AFT) track shoes (i.e., "spikes") in middle-distance events is challenging, because repeated maximal effort trials (as in sprinting) or aerobic running economy trials (as in long-distance running) are not feasible.

Methods: We introduce a novel approach to assess the benefits of AFT spikes, consisting of a series of 200-m runs at self-perceived middle-distance race pace with 10 min recovery, and conduct 4 experiments to evaluate its validity, sensitivity, reproducibility, and utility.

Results: In Experiment 1, participants ran 1.2% slower in spikes with 200 g added mass vs. control spikes, which is exactly equal to the known effects of shoe mass on running performance. In Experiment 2, participants ran significantly faster in AFT prototype spikes vs. traditional spikes. In Experiment 3, we compared 2 other AFT prototype spikes against traditional spikes on 3 separate days. Group-level results were consistent across days, but our data indicates that at least 2 separate sessions are needed to evaluate individual responses. In Experiment 4, participants ran significantly faster in 2 AFT spike models vs. traditional spikes (2.1% and 1.6%). Speed was similar between a third AFT spike model and the traditional spikes. These speed results were mirrored by changes in step length as participants took significantly longer steps in the 2 faster AFT spike models (2.3% and 1.9%), while step length was similar between the other spikes.

Conclusion: Our novel, interval-based approach is a valid and reliable method for quantifying differences between spikes at middle-distance running intensity.

Background: High adiposity and low physical activity are associated with cancer risk. Whether different amounts and intensities of physical activity can mitigate this association is unclear. We aimed to examine the independent and combined associations of adiposity and device-measured physical activity levels of different intensities with cancer incidence and mortality.

Methods: This prospective cohort study included data from 70,747 UK Biobank participants (mean age = 61.6 ± 7.9 years, mean ± SD; 56.4% women) with wrist-worn accelerometer measurements of physical activity and without chronic diseases or mobility limitations. Physical activity exposures included min per week of light intensity physical activity (LPA), moderate-to-vigorous intensity physical activity (MVPA), and vigorous intensity physical activity (VPA), along with total weekly volume. Body mass index (BMI) was calculated from anthropometric measurements. Participants were categorized into 9 groups based on joint tertiles of physical activity and BMI categories (normal weight, overweight, and obesity). Secondary analyses included adiposity using bio-impedance and waist circumference measurements. The outcome was incidence and death from cancer retrieved from national registries. Associations between adiposity, physical activity, and cancer hazard were calculated as subdistribution hazard ratios. A secondary analysis focused on cancer types strongly associated with physical activity.

Results: We observed 2625 events (2572 non-fatal and 53 fatal) during a median follow-up of 6.1 years. Compared with the referent (normal weight and high physical activity), overweight and obesity were associated with a 6% to 36% higher cancer hazard across physical activity intensities. However, high MVPA and VPA (approximately 500 min and 32 min per week in the top tertiles, respectively) attenuated the hazard associated with overweight and obesity. Being normal weight was not associated with a higher cancer hazard regardless of physical activity level. The results were similar, although more pronounced, when modeling cancer types strongly associated with physical activity as the outcome.

Conclusion: High MVPA and VPA levels may attenuate the association of overweight and obesity with cancer hazard, but maintaining a normal weight seems comparatively more important than physical activity to reduce the hazard. Maintaining a healthy body weight and engaging in physical activity is needed to minimize risk of some cancer types.

Background: Prematurely-born individuals tend to exhibit higher resting oxidative stress, although evidence suggests they may be more resistant to acute hypoxia-induced redox balance alterations. We aimed to investigate the redox balance changes across a 3-day hypobaric hypoxic exposure at 3375 m in healthy adults born preterm (gestational age ≤ 32 weeks) and their term-born (gestational age ≥ 38 weeks) counterparts.

Methods: Resting venous blood was obtained in normoxia (prior to altitude exposure), immediately upon arrival to altitude, and the following 3 mornings. Antioxidant (superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and ferric reducing antioxidant power (FRAP)), pro-oxidant (xanthine oxidase (XO) and myeloperoxidase (MPO)) enzyme activity, oxidative stress markers (advanced oxidation protein product (AOPP) and malondialdehyde (MDA)), nitric oxide (NO) metabolites (nitrites, nitrates, and total nitrite and nitrate (NOx)), and nitrotyrosine were measured in plasma.

Results: SOD increased only in the preterm group (p < 0.05). Catalase increased at arrival in preterm group (p < 0.05). XO activity increased at Day 3 for the preterm group, while it increased acutely (arrival and Day 1) in control group. MPO increased in both groups throughout the 3 days (p < 0.05). AOPP only increased at arrival in the preterm (p < 0.05) whereas it decreased at arrival up to Day 3 (p < 0.05) for control. MDA decreased in control group from arrival onward. Nitrotyrosine decreased in both groups (p < 0.05). Nitrites increased on Day 3 (p < 0.05) in control group and decreased on Day 1 (p < 0.05) in preterm group.

Conclusion: These data indicate that antioxidant enzymes seem to increase immediately upon hypoxic exposure in preterm adults. Conversely, the blunted pro-oxidant enzyme response to prolonged hypoxia exposure suggests that these enzymes may be less sensitive in preterm individuals. These findings lend further support to the potential hypoxic preconditioning effect of preterm birth.

Background: Stretching has wide appeal, but there seems to exist some mismatch between its purported applications and what the evidence shows. There is compelling evidence for some stretching applications, but for others, the evidence seems heterogeneous or unsupportive. The discrepancies even affect some systematic reviews, possibly due to heterogeneous eligibility criteria and search strategies. This consensus paper seeks to unify the divergent findings on stretching and its implications for both athletic performance and clinical practices by delivering evidence-based recommendations.

Methods: A panel of 20 experts with a blend of practical experience and scholarly knowledge was assembled. The panel meticulously reviewed existing systematic reviews, defined key terminologies (e.g., consensus definitions for different stretching modes), and crafted guidelines using a Delphi consensus approach (minimum required agreement: 80%). The analysis focused on 8 topics, including stretching's acute and chronic (long-term) effects on range of motion, strength performance, muscle hypertrophy, stiffness, injury prevention, muscle recovery, posture correction, and cardiovascular health.

Results: There was consensus that chronic and acute stretching (a) improves range of motion (although alternatives exist) and (b) reduces muscle stiffness (which may not always be desirable); the panel also agreed that chronic stretching (c) may promote vascular health, but more research is warranted. In contrast, consensus was found that stretch training does not (a) contribute substantively to muscle growth, (b) serve as an all-encompassing injury prevention strategy, (c) improve posture, or (d) acutely enhance post-exercise recovery.

Conclusion: These recommendations provide guidance for athletes and practitioners, highlighting research gaps that should be addressed to more comprehensively understand the full scope of stretching effects.

Background: Despite the wide use of compression garments to enhance athletic running performance, evidence supporting improvements has not been conclusive. This updated systematic review and meta-analysis of randomized controlled trials (RCTs) compared the effects of compression garment wearing with those of non-compression garment wearing (controls) during running on improving running performance.

Methods: A comprehensive search was conducted in the electronic databases (Web of Science, EBSCOhost, PubMed, Embase, Scopus, and Cochrane) for RCTs comparing running performance between runners wearing compression garments and controls during running, from inception to September 2024. Independent reviewers screened studies, extracted data, appraised risk of bias (RoB 2) and certainty of evidence (Grading of Recommendations Assessments, Development and Evaluation (GRADE)). Primary outcomes were race time and time to exhaustion. Secondary outcomes covered running speed and race pace, submaximal oxygen uptake, tissue oxygenation, and soft tissue vibration. Random-effects meta-analyses were conducted to generate pooled estimates, expressed in standardized mean difference (SMD). Subgroup differences of garment, race type, and contact surface were tested in moderator analyses.

Results: The search yielded 51 eligible studies comprising 899 participants, of which 33 studies were available for meta-analysis of primary outcomes. Runners wearing compression garments during running showed no significant improvement in race time (SMD = -0.07, 95%CI: -0.22 to 0.09; p = 0.40) or time to exhaustion (SMD = 0.04, 95%CI: -0.20 to 0.29; p = 0.72). Moderator analyses indicated no effects from garment type, race type, or surface. Secondary outcomes also showed no performance benefits, although compression garments significantly reduced soft tissue vibration (SMD = -0.43, 95%CI: -0.70 to -0.15; p < 0.01). Certainty of evidence was rated low to very low.

Conclusion: Data synthesis of current RCTs offers no updated evidence favoring the support of wearing compression garments during running as a viable strategy for improving running and endurance performance among runners of varying performance levels and types of running races.

Purpose: We aimed to determine: (a) the chronic effects of interval training (IT) combined with blood flow restriction (BFR) on physiological adaptations (aerobic/anaerobic capacity and muscle responses) and performance enhancement (endurance and sprints), and (b) the influence of participant characteristics and intervention protocols on these effects.

Methods: Searches were conducted in PubMed, Web of Science (Core Collection), Cochrane Library (Embase, ClinicalTrials.gov, and International Clinical Trials Registry Platform), and Chinese National Knowledge Infrastructure on April 2, with updates on October 17, 2024. Pooled effects for each outcome were summarized using Hedge's g (g) through meta-analysis-based random effects models, and subgroup and regression analyses were used to explore moderators.

Results: A total of 24 studies with 621 participants were included. IT combined with BFR (IT+BFR) significantly improved maximal oxygen uptake (VO_2max) (g = 0.63, I² = 63%), mean power during the Wingate 30-s test (g = 0.70, I² = 47%), muscle strength (g = 0.88, I² = 64%), muscle endurance (g = 0.43, I² = 0%), time to fatigue (g = 1.26, I² = 86%), and maximal aerobic speed (g = 0.74, I² = 0%) compared to IT alone. Subgroup analysis indicated that participant characteristics including training status, IT intensity, and IT modes significantly moderated VO_2max (subgroup differences: p < 0.05). Specifically, IT+BFR showed significantly superior improvements in VO_2max compared to IT alone in trained individuals (g = 0.76) at supra-maximal intensity (g = 1.29) and moderate intensity (g = 1.08) as well as in walking (g = 1.64) and running (g = 0.63) modes. Meta-regression analysis showed cuff width (β = 0.14) was significantly associated with VO_2max change, identifying 8.23 cm as the minimum threshold required for significant improvement. Subgroup analyses regarding muscle strength did not reveal any significant moderators.

Conclusion: IT+BFR enhances physiological adaptations and optimizes aspects of endurance performance, with moderators including training status, IT protocol (intensity, mode, and type), and cuff width. This intervention addresses various IT-related challenges and provides tailored protocols and benefits for diverse populations.

Purpose: Regular exercise can reduce incidence and progression of breast cancer, but the mechanisms for such effects are not fully understood. The purpose of this study was to examine the mechanisms behind the protective effects of exercise.

Methods: We used a variety of rodent and human experimental model systems to determine whether exercise training can reduce tumor burden in breast cancer and to identify mechanism associated with any exercise training effects on tumor burden.

Results: We show that voluntary wheel running slows tumor development in the mammary specific polyomavirus middle T antigen overexpression (MMTV-PyMT) mouse model of breast cancer but only when mice are not housed alone. We identify the proteoglycan decorin as a contraction-induced secretory factor that systemically increases in patients with breast cancer immediately following exercise. Moreover, high expression of decorin in tumors is associated with improved prognosis in patients, while treatment of breast cancer cells in vitro with decorin reduces cell proliferation. Notwithstanding, when we overexpressed decorin in murine muscle or injected recombinant decorin systemically into mouse models of breast cancer, elevated plasma decorin concentrations did not result in higher tumor decorin levels and tumor burden was not improved.

Conclusion: Exercise training is anti-tumorigenic in a mouse model of luminal breast cancer, but the effect is abrogated by social isolation. The proteoglycan decorin is an exercise-induced secretory protein, and tumor decorin levels are positively associated with improved prognosis in patients. The hypothesis that elevated plasma decorin is a mechanism by which exercise training improves breast cancer progression in humans is not, however, supported by our pre-clinical data since elevated circulating decorin did not increase tumor decorin levels in these models.