Journal of Sport and Health Science最新文献

Background: While Nordic hamstring exercise (NHE) training has been shown to reduce hamstring strains, the muscle-specific adaptations to NHE across the 4 hamstrings remain unclear. This study investigates architectural and microstructural adaptations of the biceps femoris short head (BFsh), biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) in response to an NHE intervention.

Methods: Eleven subjects completed 9 weeks of supervised NHE training followed by 3 weeks of detraining. Magnetic resonance imaging was performed at pre-training, post-training, and detraining to assess architectural (volume, fiber tract length, and fiber tract angle) and microstructural (axial (AD), mean (MD), radial (RD) diffusivities, and fractional anisotropy (FA)) parameters of the 4 hamstrings.

Results: NHE training induced significant but non-uniform hamstring muscle hypertrophy (BFsh: 22%, BFlh: 9%, ST: 26%, SM: 6%) and fiber tract length increase (BFsh: 11%, BFlh: 7%, ST: 18%, SM: 10%). AD (5%), MD (4%), and RD (5%) showed significant increases, but fiber tract angle and FA remained unchanged. After detraining, only ST showed a significant reduction (8%) in volume, which remained higher than the pre-training value. While fiber tract lengths returned to baseline, AD, MD, and RD remained higher than pre-training levels for all hamstrings.

Conclusion: The 9-week NHE training substantially increased hamstring muscle volume with greater hypertrophy in ST and BFsh. Hypertrophy was accompanied by increases in fiber tract lengths and cross-sections (increased RD). After 3 weeks of detraining, fiber tract length gains across all hamstrings declined, emphasizing the importance of sustained training to maintain all the protective adaptations.

Exercise is a therapeutic approach in cancer treatment, providing several benefits. Moreover, exercise is associated with a reduced risk for developing a range of cancers and for their recurrence, as well as with improving survival, even though the underlying mechanisms remain unclear. Preclinical and clinical evidence shows that the acute effects of a single exercise session can suppress the growth of various cancer cell lines in vitro. This suppression is potentially due to altered concentrations of hormones (e.g., insulin) and cytokines (e.g., tumor necrosis factor alpha and interleukin 6) after exercise. These factors, known to be involved in tumorigenesis, may explain why exercise is associated with reduced cancer incidence, recurrence, and mortality. However, the effects of short- (<8 weeks) and long-term (≥8 weeks) exercise programs on cancer cells have been reported with mixed results. Although more research is needed, it appears that interventions incorporating both exercise and diet seem to have greater inhibitory effects on cancer cell growth in both apparently healthy subjects as well as in cancer patients. Although speculative, these suppressive effects on cancer cells may be driven by changes in body weight and composition as well as by a reduction in low-grade inflammation often associated with sedentary behavior, low muscle mass, and excess fat mass in cancer patients. Taken together, such interventions could alter the systemic levels of suppressive circulating factors, leading to a less favorable environment for tumorigenesis. While regular exercise and a healthy diet may establish a more cancer-suppressive environment, each acute bout of exercise provides a further "dose" of anticancer medicine. Therefore, integrating regular exercise could potentially play a significant role in cancer management, highlighting the need for future investigations in this promising area of research.

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.