International journal of sports medicine最新文献

Bruxism, an involuntary clenching or grinding of teeth, is increasingly prevalent among athletes due to elevated stress, performance anxiety, and intense training. This systematic review analyzed 11 studies (2000-2023) on bruxism prevalence, underlying factors, and its impact on athletic performance. Data were extracted on prevalence, strength, endurance, coordination, reaction time, psychological stress, sleep quality, and injury risk. Random-effects models calculated pooled prevalence, standardized mean differences, and odds ratios. Bruxism prevalence among athletes ranged from 15 to 70%, with a pooled estimate of 38% (95% confidence interval: 25-52%), significantly higher than the general population's 8-20%. Combat sports (58%) and weightlifting (50%) showed the highest rates. Athletes with bruxism exhibited reduced strength (standardized mean difference=- 0.48), endurance (standardized mean difference=- 0.41), coordination (standardized mean difference=- 0.45), slower reaction times (standardized mean difference=- 0.33), elevated anxiety (standardized mean difference=0.62), poorer sleep quality (standardized mean difference=- 0.56), and a 2.5-fold higher injury risk (odds ratio=2.5). Bruxism poses significant challenges for athletes, compromising oral health, sleep, and performance. Further research should clarify sport-specific risk factors and develop targeted management strategies to safeguard athletes' health and competitive outcomes.

Heat stress and hypoxia impair athletic performance through inflammation, muscle injury, and neuromuscular dysfunction. This study examined these effects in 15 endurance athletes (13 males and 2 females, VO_2max=59.5±3.9 ml/min/kg) performing incremental load tests to exhaustion under normal (CON), hypoxic (HYP), and high-temperature and humidity (HOT) conditions. Pre- and postexercise assessments, including blood biomarkers, performance, and surface electromyography (sEMG) during the counter-movement jump (CMJ) and isometric mid-thigh pull (IMTP), were conducted under normal conditions. Compared to CON, time to exhaustion was significantly reduced in HYP and HOT (p<0.05). CMJ performance declined under CON and HYP (p<0.05). Force at 200 and 250 ms decreased under both CON and HYP during IMTP (p<0.05). The root mean square (RMS) and the median power frequency (MPF) were decreased under HYP during CMJ and IMTP (p<0.05). In contrast, no significant differences in sEMG and kinetic markers were observed in the HOT (p>0.05). No significant changes in creatine kinase and lactate dehydrogenase levels were observed (p>0.05). Postexercise, tumor necrosis factor-alpha was lower in HYP (p<0.05), while interleukin-6 increased in HOT (p<0.05). Hypoxia impairs neuromuscular function and suppresses inflammation, whereas heat stress induces inflammation without neuromuscular deficits.

The aim of this study was to determine if a 5-day training cycle in professional sports team athletes caused acute and subacute alterations in Achilles tendon (AT) echo intensity (EI). The study included 24 men and 24 women of football, handball, and volleyball teams from the top national leagues. During their respective competition periods, eight players from each team were monitored in every training session over a 5-day training cycle. It involved monitoring AT EI, cross-sectional area with ultrasound, subjective feelings of fatigue, and perceived exertion throughout the training cycle. The results revealed a significant acute and subacute effect on EI at distal (p<0.001), middle (p<0.001), and proximal (p<0.001) AT locations. The acute effect had a significant impact on the subacute changes in EI at all locations (p<0.001). A significant interaction of athletes' biological sex, the acute effect was only observed in the distal AT (p=0.013). The study revealed a significant decrease in AT EI following team sports training sessions for men and women. A consistently reduced EI of the AT during the 5-day training cycle suggests that repetitive loading likely induces structural changes in the tendon.

Anterior cruciate ligament reconstruction induces deleterious neuromuscular alterations. Musculoskeletal ultrasonography provides an accessible method to quantify muscle size and quality in patients with anterior cruciate ligament reconstruction who suffer from persistent skeletal muscle atrophy. This study compares rectus femoris and vastus intermedius muscle thicknesses and echo intensities using extended field-of-view ultrasonography in individuals with a history of anterior cruciate ligament reconstruction versus non-injured controls. Twenty-six individuals with previous anterior cruciate ligament reconstruction and 20 controls were participated in this study. Extended field-of-view ultrasonography was used to analyze the muscle thickness in the proximal, middle, and distal regions of the thigh, while the echo intensity was measured to assess the muscle quality. Findings indicate significant asymmetries in the muscle thickness (p<0.01 and η _p ²=0.312) and echo intensity (p=0.024 and η _p ²=0.111) for the anterior cruciate ligament reconstruction group, favoring the uninvolved leg, with no site-specific differences between groups. Results show muscle-specific size differences, with greater vastus intermedius muscle thickness than rectus femoris muscle thickness in controls (p<0.01 and d=0.609), but no difference between muscles in either leg of the anterior cruciate ligament reconstruction group (p>0.05 and d=0.094). Overall, these results highlight unique skeletal muscle changes between the biarticular rectus femoris and the monoarticular vastus intermedius following anterior cruciate ligament reconstruction, likely reflecting postoperative deficiencies in knee extensor function.

This research analyzed the validity of the level of effort method to practically prescribe relative intensity (%1RM) and velocity loss (%VL) in women. We examined the (i) inter- and intrasubject (test-retest) variabilities in the number of repetitions to failure (nRM) at different%1RMs and (ii) the relationship between the repetitions being completed and%VL being incurred. Analyses covered three%1RMs (65-75-85%1RM), two exercises [bench press (BP) and squat (SQ)], and two groups of women with different strength levels (high and low, n=12 per group). To analyze the inter- and intrasubject variabilities, women completed two rounds of repetition-to-failure tests against the aforementioned%1RMs. Velocity was monitored to examine the relationship between the repetitions being completed and%VL incurred. For both strength groups, exercises, and%1RMs examined, the nRM showed very low inter- (95% confidence interval≤4 repetitions) and intrasubject (standard error of measurement≤1.7 repetitions) variabilities. Very close fits were found for individual's relationships between the repetitions being completed and the%VL incurred for the low (BP, mean R ²=0.975, SQ, mean R ²=0.938) and high (BP, mean R ²=0.975, SQ, mean R ²=0.934) strength groups. In conclusion, the level of effort method is a technology-free approach to program%1RM and%VL in women.

This study compares locomotor activities during matches with different recovery intervals (<72, 72-120, 121-168,>168 h), considering accumulated travel distances (0, 1-250, 251-1,000,>1,000 km) in the previous 3, 5, and 7 days, and match sequence during congested periods. Locomotor data were collected using a global navigation satellite system and included total distance, distance covered between 14-20, 20-25, 25-30, and>30 km/h, maximal speed, maximal accelerations and decelerations, and the number of accelerations and decelerations between 2 and 3 m/s². Congested fixtures (<72 and 72-120 h) negatively affected locomotor activities compared to noncongested ones (>168 h), with players covering less total distance (p=0.026) and distance at 14-20 km/h (p=0.027) and performing fewer accelerations (p=0.001) and decelerations (p=0.022) between 2 and 3 m/s². Additionally, interactions with accumulated kilometers traveled revealed that high accumulated distances in the days leading up to congested fixtures exacerbated reductions in locomotor performance (p<0.05). Analysis of specific cases of consecutive congested fixtures showed a decline in locomotor activities after three matches within<72 hours or four matches within<120 hours. These findings highlight the importance of managing fixture schedules and travel distances to optimize player performance and reduce the risk of injury during congested match periods, with limiting players to short match sequences potentially being beneficial.

This study aimed to compare the intensity when thresholds occur determined with muscle oxygen saturation and blood lactate concentration during a graded exercise test (GXT) in an arm-crank ergometer. Twenty-nine participants were included, divided into non-spinal cord injury (SCI) (N=12) and SCI (N=17) groups. Participants underwent a GXT with 3-minute steps and 1-minute rest intervals. Blood lactate concentration was measured at baseline and after each step, while muscle oxygen saturation was continuously registered in the biceps brachii. Agreement between methods was good at the first threshold [Non-SCI: intraclass correlation coefficient (ICC)=0.46; SCI: ICC=0.51] and excellent at the second threshold (Non-SCI: ICC=0.82; SCI: ICC=0.92). No significant differences were found between groups in bias for the first and second lactate thresholds (p > 0.05). In conclusion, muscle oxygen saturation is valid and reliable for the second lactate threshold determination, with stronger agreement than the first lactate threshold during GXTs using arm-cranking in biceps brachii in Non-SCI and SCI.

The study aimed to investigate the effects of exercise-induced muscle damage on muscle and cerebral oxygenation. Twelve healthy men performed eccentric exercise on a leg press machine at an intensity corresponding to their concentric one-repetition maximum. Muscle damage indices, muscle and cerebral oxygenation, and vastus lateralis architecture were evaluated at baseline and 48 hours postexercise. At 48 hours postexercise, delayed onset muscle soreness significantly increased (1.0±0.3 to 4.2±2.8; p<0.01), while concentric one-repetition maximum, maximal isometric force, and rate of force development decreased (p<0.01). The quadriceps' cross-sectional area and muscle thickness significantly increased (p<0.05). During a 5-second maximal isometric contraction, the tissue oxygen saturation index (TSI) of the vastus lateralis (63±3-61±4%; p>0.05) and the prefrontal cortex (68±2-67±1%; p>0.05) did not change significantly. Deoxyhemoglobin showed a marginally significant decrease (1.16±1.14-0.06±1.10 µM; p=0.049). No significant changes were observed in muscle and cerebral oxygenation parameters during the 30-second maximal isometric contraction. The eccentric exercise protocol induced muscle damage and altered muscle architecture. However, these changes were not sufficient to affect muscle or cerebral TSI during either short- or long-duration maximal isometric contraction. Eccentric exercise-induced muscle damage was not found to induce changes in cerebral oxygenation.

The aim of this review was to examine how mean muscle length during resistance training (RT) influences regional muscle hypertrophy. Three databases were screened for relevant studies that manipulated muscle length through range of motion or exercise selection and evaluated regional muscle hypertrophy. Twelve studies conducted among young adults were included in the Bayesian meta-analysis. Standardized mean differences (SMDs) indicated trivial hypertrophic effects estimated with relatively high precision between proximal (25% muscle length; SMD: 0.05 [95% quantile interval {QI}:-0.07, 0.16]; exponentiated log-transformed response ratio [lnRR]: 0.57% [95% QI:-1.92%, 3.24%]), mid-belly (50% muscle length; SMD: 0.07 [95% QI:-0.02, 0.15]; exponentiated lnRR: 1.22% [95% QI:-0.77%, 3.22%]), and distal (75% muscle length; SMD: 0.09 [95% QI:-0.01, 0.19]; exponentiated lnRR: 1.88% [95% QI:-0.44%, 4.34%]) sites. The effects of RT at longer muscle lengths showed an increasing trend from proximal to distal sites. However, the percentage of posterior distributions falling within regions of practical equivalence was high across all sites. Our findings suggest that RT at both longer and shorter mean muscle lengths produces similar hypertrophic effects. Relatively small differences between "shorter" and "longer" mean muscle length (an average difference of 21.8% mean muscle length) between conditions/groups in the examined studies warrant caution when interpreting the findings.

We aimed to compare the anaerobic alactic (AnAL) energy expenditure from a 50-m front crawl swimming between two methodologies in highly trained short-distance swimmers: (i) based on the maximal phosphocreatine (PCr) splitting in contracting muscles (AnAL_PCRSPLITTING) and (ii) based on the oxygen uptake ( ˙VO₂) off-kinetics, where AnAL is estimated from the area under the curve of the fast component (amplitude in liters×time constant in minutes) of the 10-minute of excess postexercise oxygen consumption (AnAL_VO2KINETICS). Thirty-nine 50-m front-crawl all-out (time trial) swimming performances and respective off-transient kinetics pulmonary  ˙VO₂ samples (23 men: 17.0±2.6 y and; 16 women: 17.0±2.1 y) were analyzed. We observed no differences (η ² _p=0.044; p=0.068) between AnAL_PCRSPLITTING (41.7±6.1 kJ) and AnAL_VO2KINETICS (37.6±12.7 kJ). Bland-Altman plots indicated high bias (3.79-4.42 kJ) and precision (agreement) (limits:-21.31 to 30.14 kJ) between methods, with repeatability ranging from "poor" to "moderate" (intraclass correlation coefficients: 0.34-0.53; p=0.018-0.157), indicating proportional error that varies with the magnitude of the measurements. Although both methods showed overall agreement, their conceptual and methodological differences introduce proportional error. Thus, they should not be used interchangeably, but rather considered complementary, when feasible, to provide a more comprehensive understanding of AnAL energy expenditure in short-duration maximal efforts such as 50-m swimming.