Journal of Sports Medicine and Physical Fitness最新文献

Background: Post-activation potentiation (PAP) can elicit increased force in a muscular contraction following a specific preparatory activity, though little research exists regarding how various loading methods in said activity impact the potentiation effect. This study seeks to determine if banded PAP activities are more effective than static loading in improving power production.

Methods: Participants in this randomized cross-over design study were 7 female collegiate volleyball players with a 6-month minimum training age and no significant injuries. The study took place across 3 sessions, each 48 hours apart. At the 1^st session, baseline vertical jump height (cm), power (W), and 1RM back squat were taken, and subjects were randomly placed into one of two different PAP activity groups at the 2^nd and 3^rd sessions. PAP activity was standardized to 2 sets of 2 back squats at 90% 1RM with a 3-second eccentric, with the variance in groups being the inclusion or exclusion of 20% of the load from elastic resistance bands. Following the PAP activity, and an 8-minute rest, subjects performed 3 vertical jumps.

Results: The PAP band-resisted activity group showed significant improvements in vertical jump height (P=0.006) and power (P=0.006) when analyzed with an ANOVA repeated measures test. No significant difference was found in the same analysis with the non-banded group for height (P=0.512) or power (P=0.517), and there were no significant differences found between group peak performance or averages when comparing between groups. A priori power analysis showed sufficient statistical significance despite the small sample size (1 - β=0.95).

Conclusions: This study was conducted utilizing barbell back squats as the potentiation activity with the dynamic variable being 20% of the load being from elastic band resistance, and a standardized rest period of 8 minutes before testing the potential impact this PAP activity had on vertical jump performance. Utilizing PAP activities that are specific to the demands of a given sport may improve vertical jump and power capabilities within athletes.

Background: Medial Tibial Stress Syndrome is associated with the stiffness of flexor digitorum longus (FDL) muscle. Therefore, it is necessary to reduce the load on FDL. Stretching has been reported to immediately reduce muscle stiffness and decrease maximal muscle strength. Thus, stretching the FDL may reduce its stiffness and stress. Additionally, the decrease in muscle strength due to stretching may be compensated by other cooperative muscles. This study aimed to determine how selective stretching of the FDL before exercise affects the stiffness of the FDL and its cooperative muscles after exercise.

Methods: Twenty-one healthy young men were enrolled in this crossover study. The elastic modulus of the FDL, tibialis posterior (TP), soleus, and flexor hallucis longus muscles were measured. The intervention trial involved selective stretching of the FDL. Subsequently, an eccentric ankle inversion exercise was performed, and the elastic modulus of each muscle was measured. The control trial consisted of resting in a sitting position instead of stretching.

Results: A significant interaction was observed for the elastic modulus of the FDL, the elastic modulus increased significantly only in the control trial after exercise. A main effect of timing was found only for the TP, and neither a main effect nor an interaction effect was found for any of the other muscles.

Conclusions: Selective stretching of the FDL muscle before exercise prevented an immediate increase in its stiffness after exercise, but there was no such effect following changes in muscle stiffness caused by exercise in the other cooperative muscles.

Background: This study analyses whether sweep rowers (port, starboard), who in the boat row in an asymmetric movement, sit on the seat of the rowing ergometer in a different manner from scullers, who on the boat row in symmetric manner.

Methods: Twenty-five male rowers (9 scull and 16 sweep: 8 port and 8 starboard) each performed a 90-min endurance training on rowing ergometer. Any displacement sideways of the rowers on the seats was measured from images of back of the rower at 30, 60 and 90 min.

Results: Scullers were seated in the expected manner maintaining centrality of the seat (distance from center at 30, 60, 90 min = 0.3±0.5 cm; 0.3±0.5 cm, 0.6±0.5 cm) in contrast with portside rowers who shifted to the left (30, 60, 90 min = -3.0±1.1 cm; -3.6±1.1 cm; -3.5±0.9 cm) and starboard rowers who shifted to the right (30, 60, 90 min = 3.1±2 cm; 3.9±1.6 cm; 3.4±1.4 cm). Shifted seating for sweep rowers was consistently observed to the opposite side to which they rowed.

Conclusions: The type of rowing on the boat influenced how rowers sit on the ergometer with sweep rowers consistently adopting a seating position shifted to opposite side to the one they rowed. This can be interpreted in terms of neural memory of prior postural adjustments and calls for further monitoring as asymmetry in seating may lead to uneven loading, particularly relevant to athletes with large training volume and density and when rowing in more "extreme" rowing settings, for example, coastal rowing / beach sprints events.

Background: Physical activity (PA) has a direct influence on body composition, particularly in terms of lean body mass (LBM) and fat mass (FM). This study assesses how lifelong changes in PA impact body mass index (BMI) and body composition using data from NHANES (1999-2006) for adults aged 29 to 59 years.

Methods: Data were extracted from the National Health and Nutrition Examination Survey (1999-2006), including male and female participants aged 29-59. The cross-sectional analysis focused on the relationship between BMI and the fat mass index (FMI)/Lean Body Mass Index (LBMI) ratio, adjusted for height (ht). Multivariate linear regression models were adjusted for covariates and stratified by sex. All analyses were adjusted considering the sample weights.

Results: The analysis comprised 5115 participants, with 51.7% male and an average age of 42.8±0.13 years. The FMI/ht-LBMI ratio is approximately 0.4 for men and 0.7 for women. The results indicated that women had a mean BMI increase (β=1.9, 95% CI: 1.4-2.4) for every 0.1 increase in the FMI/ht-LBMI ratio, while men had a mean BMI increase (β=1.0, 95% CI: 0.7-1.4) (P<0.05), compared to those maintaining the same PA pattern over ten years. Additionally, factors such as socioeconomic status, race/ethnicity, and nutritional status at age 25 were found to significantly impact body composition outcomes.

Conclusions: In summary, long-term PA emerges as a modifier in population-level body composition. Individuals with a history of lower PA over the last decade showed a higher proportion of adipose tissue. In this way, the importance of maintaining substantial levels of PA throughout life is emphasized, contributing positively to body composition.

Background: Football injuries pose substantial risks to player health, team performance, and club finances. Although injury prevention is a key priority, most epidemiological studies focus on short-term data from international tournaments or clubs outside Germany. This study aimed to examine the injury epidemiology in German elite men's football through a long-term analysis of a single club competing in both top national leagues.

Methods: A professional German football team was prospectively observed over eight consecutive seasons, with four seasons played in the first division and four in the second. Injury incidence and associated time loss were analyzed using Poisson regression.

Results: A total of 357 match injuries and 625 training injuries were recorded. Injury incidence did not significantly differ between the first and second division, either for match play (79.0 vs. 80.8 injuries per 1000 match hours, P=0.83) or training (8.7 vs. 9.2 injuries per 1000 training hours, P=0.49). However, average time loss was significantly greater in the first division for both training injuries (70 vs. 49 days per 1000 training hours, P<0.01) and match injuries (653 vs. 596 days per 1000 match hours, P=0.017).

Conclusions: Although injury incidence was comparable between the two top German divisions, injuries sustained in the first division led to significantly greater time loss. These findings highlight the importance of addressing not only the frequency but also the severity of injuries in elite football injury prevention strategies.

Background: Adductor-related groin pain syndrome (ARGPS) is a common overuse injury encountered in sports requiring quick accelerations and decelerations, changes of direction and kicking. If conservative treatment fails, ARGPS can be surgically treated with adductor longus tenotomy (ALT). Four types of ALT are described in literature: two are different types of partial tenotomy (PT1 and PT2) and two are two different types of total tenotomy (TT1 and TT2). The aim of this study was to compare these four different types of ALT in athletic populations affected by ARGPS.

Methods: In this retrospective study (level of evidence IV), four study groups of soccer players at different athletic levels were considered. G1 grouped 12 male patients subjected to partial ALT (PT1), G2 included 13 male patients subjected to partial ALT with a surgical technique (PT2) different to that employed in G1, G3 grouped 10 male patients subjected to total ALT (TT1) and G4 included 10 male patients subjected to total ALT with a different surgical technique (TT2) to G3.

Results: The percentage of subjects who resumed sporting activities and the return to play (RTP) times were respectively 83% and 7.5±3.8 months, 100% and 4.0±0.4 months, 100% and 3.1±0.5 months, 100% and 2.4±0.4 months for the study groups G1, G2, G3 and G4. The percentage of subjects that returned to sport was significantly lower (P<0.05) in G1 while the time for RTP was significantly lower (P<0.05) in G4.

Conclusions: Of all the surgical techniques employed in ALT, the TT2 surgical technique entails a lower complication rate and allows for the quickest RTP in athletic populations.

Background: Physical activity (PA) improves health and quality of life, while providing an effective coping strategy against burnout. This study assessed PA levels among medical students and junior doctors in Malta, exploring demographic differences and relationships with anxiety, energy drink/coffee consumption, and career progression, addressing a gap in the literature.

Methods: Two hundred twenty-nine participants (161 medical students; 68 foundation year doctors; mean age=22.90 years) completed an online questionnaire including demographic data, standardized measures of PA (GLTEQ) and anxiety (GAD-7) and questions on energy drink/coffee consumption and career progression.

Results: Results revealed a significant negative relationship between PA and age, rs(227)=-0.14, P=0.04. Males carried out more PA (OR=1.82, 95% CI, 1.12 to 2.94) than females (U=4671.00, z=-2.42, P=0.02); this gender difference in PA was present in medical students (P=0.01) not junior doctors (P=0.75). Male junior doctors were less anxious than females (U=319.00, z=-2.32, P=0.02); no significant gender difference in anxiety was revealed in medical students (P=0.76). No significant correlation was found between PA and anxiety (P=0.41) or energy drink consumption (P=0.81, 1.00). No difference in PA levels was revealed between medical students and junior doctors (P=0.09).

Conclusions: Further research is needed to compare PA levels between medical and general populations. The findings underscore the importance of including PA in medical curricula for students'/doctors' wellbeing and for effective lifestyle advice.

Background: Although high muscle oxygenation dynamics in active muscles are expected to decrease cardiac workload and ventilation associated with carbon dioxide excretion at an exercise at equivalent peak oxygen uptake (VO2) loads in the whole body, these relationships remain unclear. The aim of this study was to investigate whether high muscle oxygenation dynamics contribute to reduced cardiac workload and ventilation during exercise.

Methods: Twenty-three healthy young males were enrolled in this cross-sectional study and divided into two groups: the low muscle oxygenation dynamics group (N.=11) and the high muscle oxygenation dynamics group (N.=12), based on the change in muscle oxygen saturation (SmO2) in the right vastus lateralis from rest to peak VO2. All participants underwent cardiopulmonary exercise testing to assess the double product, cardiac workload, carbon dioxide production (VCO2), and expiratory minute volume as ventilation parameters associated with carbon dioxide excretion.

Results: Linear mixed-effect models with double product, VCO2/body mass or expiratory minute volume/body mass as the dependent variable, individual as random effects, and the group and metabolic equivalents (METs) as fixed effects revealed significant interactions between the group and METs (all P<0.001). Multiple comparison results demonstrated that the double product, VCO2/body mass at 5-8 METs, and expiratory minute volume/body mass at 6-8 METs were significantly lower in the group with high muscle oxygenation dynamics than in the group with low muscle oxygenation dynamics.

Conclusions: High muscle oxygenation dynamics contribute to reduced cardiac workload and ventilation associated with carbon dioxide excretion during exercise.

Background: Wearing a mandibular repositioning dental splint may enhance ventilatory function and exercise performance. We aim to analyze the performance and the biophysical effects of wearing an intraoral splint with mandibular repositioning when running until exhaustion at moderate intensity.

Methods: Sixteen trained male runners completed a crossover randomized controlled study to evaluate the effects of two intraoral splints (with and without mandibular forward repositioning) on performance, ventilatory and bioenergetic profiles during running until exhaustion at the velocity corresponding to the anaerobic threshold. Ventilatory variables were analyzed at different running time-points, and a paired samples t-test was employed to compare the experimental conditions across all evaluated variables.

Results: The splint with mandibular forward repositioning facilitated ~12% longer running than the splint without mandibular repositioning. Oxygen uptake was the sole ventilatory variable demonstrating a higher value across all the analyzed running time-points when the mandible was advanced (10^th min, 58.1±9.4 vs. 55.3±9.8; 10 min before the end, 57.7±8.7 vs. 55.3±9.1; and at the end of the exercise, 57.2±8.2 vs. 54.2±9.0 mL∙kg^-1∙min^-1; P≤0.05). The splint with mandibular forward repositioning also elicited a lower rate of perceived exertion (17.1±0.77 vs. 17.4±0.63, P=0.05) and higher aerobic contribution (2611±708 vs. 2212±640 kJ), overall energy spent (2633±708 vs. 2232±642 kJ) and exercise energy cost (0.28±0.05 vs. 0.26±0.05 kJ∙m-1, P≤0.005).

Conclusions: The mandibular forward repositioning elicited a marked improvement in moderate intensity performance, with beneficial physiological and perceived effects.

Background: Exercise intensity is commonly determined using maximal heart rate and maximal oxygen uptake. However, blood lactate levels at different exercise intensities are considered more sensitive biomarkers of endurance performance than maximal oxygen uptake. This study evaluated the validity of exercise intensity determined by blood lactate levels during running and determine the dynamics of blood glucose and β-hydroxybutyrate levels during high- and low-intensity running exercise.

Methods: Exercise intensities for 12 participants were determined using the lactate curve test. Each participant performed four running tests: low-intensity 30-min, high-intensity 30-min, and low-intensity 60-min running, and no-running (control) tests, with intervals of 1 day to 2 weeks. Blood glucose and β-hydroxybutyrate levels were measured using fingertip puncture blood sampling before and every 30 min (up to 240 min) after the start of running.

Results: Blood glucose levels increased significantly immediately after high-intensity 30-min running test compared to the 0-time point. Blood glucose levels decreased to similar levels as that in the 0-min time point 30 min after the 30-min running test. β-hydroxybutyrate levels increased significantly every 30 min after the 150-min time point compared to the levels in the 0-min time point in the high-intensity 30-min and low-intensity 60-min running tests.

Conclusions: Using blood lactate measurements obtained from a simple device, we established high-intensity exercise conditions producing transient post-exercise blood glucose increases. Changes in glucose and β-hydroxybutyrate levels reflected energy metabolism shifts across exercise conditions. Further investigation of additional metabolic indicators will help clarify energy metabolism mechanisms at varying exercise intensities.