There is scarcity of studies using device-based measures to examine how relationship and parenthood transitions modify 24-h movement behaviors. This study examined how the composition of 24-h movement behaviors changes during these life transitions. Young adults (n = 170, mean age 25.6 years, SD 0.6) from the Special Turku Coronary Risk Factor Intervention Project (STRIP) wore wrist-worn accelerometers for 1 week and completed questionnaire at ages 26 and 31 years. Participants were categorized by relationship status into single (16%), those transitioning from single to partnered (31%), partnered (47%), and separated (7%), and by parenthood status into non-parents (73%), new parents (19%), and parents (8%). Changes in daily movement behaviors, including sleep, sedentary behavior (SED), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA), were examined using compositional linear mixed models. In general, LPA and MVPA decreased relative to sleep and SED (p = 0.007). Differences emerged between LPA and MVPA in relationship and parenthood groups (p for group × time interaction 0.008 and 0.001). Those transitioning to partnership decreased MVPA by 17 min/day, while partnered and separated individuals showed no notable MVPA change but decreased LPA by 14 and 43 min/day. Single individuals and non-parents decreased LPA and MVPA in similar proportions. New parents decreased MVPA by 20 min/day, while parents increased it by 19 min/day. Becoming first-time parent and starting relationship was associated with decline of MVPA. Our results suggest the importance of considering these life transitions and providing guidance for maintaining physical activity despite changes in life situations.

Panoramic ultrasound (US) is an extended field-of-view (EFOV) imaging technique that enables visualization of large-scale skeletal muscles. This technique has previously been found to produce valid and reliable quantifications of muscle morphology in primarily young male subjects. The purpose was to investigate the intra-rater between-session test-retest reliability of panoramic US imaging for determining vastus lateralis (VL) and rectus femoris (RF) cross-sectional area (mCSA) in healthy middle-aged to elderly adults. In this cross-sectional study, axial panoramic US images of the RF and VL muscles were captured in 23 healthy females and males aged 47 to 78. Assessed across two sessions 3-7 days apart, intra-rater reliability was evaluated by intraclass correlation coefficients (ICC), within-subject coefficient of variation , standard error of measurement (SEM), and minimal detectable change (MDC). Mean mCSA for RF was mean ± SD, 7.5 ± 2.7 cm on both test days, with a numeric difference of 0.8%. Mean VL mCSA was 20.6 ± 6.6 cm and 20.5 ± 6.5 cm on test days 1 and 2, respectively. Test-retest ICC were: 0.997 (95% CI: 0.994-0.999) for RF and 0.995 (95% CI: 0.989-0.998) for VL. was 2.6% for RF and 2.4% for VL. SEM was 0.2 cm for RF and 0.5 cm for VL. MDC was 0.4 cm for RF and 1.3 cm for VL. In conclusion, panoramic EFOV US is a highly reliable imaging technique for assessing RF and VL mCSA in middle-aged and elderly adults. These findings endorse the clinical and research utility of EFOV US and its sensitivity for detecting even minor changes in skeletal muscle size.

Competitive skiing has gained increasing popularity among adolescent, yet it comes with injury risks. The aim was to determine injury incidence, type and time of injury, localization, and diagnosis, among adolescent competitive skiers (alpine, cross-country, ski-cross, mogul), and to compare between skiing discipline, sex, and high school year. All students (n = 190) enrolled in a ski high school from August 2013 to June 2018 were included. All injuries during the study period were prospectively registered by the physiotherapist at the high school. Demographic and injury data were registered. Absolute injury incidence (injuries/100 skiers) was calculated. In total, 166 (87%) skiers reported 502 injuries, which corresponds to an absolute injury incidence of 264.2 injuries/100 skiers during the 5-year follow-up. A higher injury incidence was shown in school year 1 compared with year 2-4 (131.3 vs. 79.5-98.4; p < 0.05). No differences in injury incidence were found between sex or skiing discipline. Females were more prone of having a gradual-onset injury compared with males (179.3 vs. 96.3; p < 0.001). Mogul skiers had higher incidence of acute injuries compared with the other disciplines (220.0 vs. 71.4-160.0; p < 0.001). The knee was the most common localization across all skiing disciplines, except for cross-country (lower leg). Low back pain was the predominant diagnosis, except in ski-cross (concussion). Skiers attending specialized ski high schools exhibited a significantly high injury incidence, with first-year students being the most susceptible to injuries, across all skiing disciplines and both sexes. While the knee was the most common injury location, concussion was remarkably frequent, particularly among ski-cross skiers.

Surfing bottom turns underpin the quality of subsequent maneuvers, and surfing performance overall. Despite this, no study has investigated coaching cues to determine their association with performance. This study investigated the frontside bottom turn, to identify critical features associated with quality performance, and second to determine whether any of these features could predict whether a surfer would subsequently perform either a cutback or a top turn maneuver. Videos of every frontside bottom turn from all finals heats of the 2017 World Surf League, Corona Open Jeffrey's Bay event were analyzed. A total of 199 frontside bottom turns were identified and categorized as either a bottom turn leading to a cutback maneuver (n = 106), or a bottom turn leading to a top turn maneuver (n = 93). A checklist of 47 potential critical features was developed after consultation with coaching and competition judging experts, thereby enabling a systematic analysis of each turn to determine the expected and actual frequency of occurrence for each potential feature. Consequently, an extensive list of critical features of the frontside bottom turn was identified and associated with a high level of performance, being executed successfully by professional athletes during high-stakes competition. Several features, particularly during the exit phase of the bottom turn, also helped predict whether these athletes subsequently performed either a cutback or a top turn maneuver. The findings of this study provide surf coaches with cues that can be used as a guide to effectively coach two main frontside bottom turn variations.

The decline in fitness levels among children and adolescents underscores the urgent need for effective exercise interventions. Aerobic endurance training (ET) and resistance training (RT) are vital for physical development in this demographic. This study employs multivariate and network meta-analysis (NMA) to assess the impact of concurrent training (CT), which integrates both ET and RT, on youth physical fitness. The objective is to identify the distinct advantages of CT over either ET or RT alone, emphasizing demographic and training-specific variables. A systematic literature review of publications from 1980 onward was conducted through ISI Web of Science, PubMed/MEDLINE, and SPORTDiscus databases, adhering to the PICOS criteria for study selection. Data were analyzed using univariate, multivariate, and network meta-analyses in Stata 17.0, focusing on cardiorespiratory fitness and muscular strength. The methodological quality and risk of bias were evaluated using the PEDro scale and Egger's test, along with sensitivity analyses and meta-regression to explore heterogeneity and publication bias. This analysis included 36 studies with 2658 participants (mean age: 14.32 ± 2.29 years) from an initial 11 074 publications, indicating low bias risk (PEDro scores ≥ 6). Univariate meta-analysis showed no significant differences in maximal oxygen uptake (VOmax) between CT and ET (standardized mean difference [SMD] = 0.01; 95% confidence interval [CI]: -0.23 to 0.25; p = 0.93). In contrast, CT significantly improved countermovement jump (CMJ) compared to RT alone (SMD = 0.19; 95% CI: 0.01-0.36; p = 0.04). Multivariate analysis confirmed notable enhancements in endurance and explosiveness for CT compared to ET or RT. NMA indicated significant improvements in lower limb strength, CMJ, and VOmax across interventions compared to controls, with the consecutive resistance training followed by ET (CRE) group yielding the most significant CMJ improvement (SMD = 0.27; 95% CI: 0.07-0.47). Isolated RT showed the highest lower limb strength improvement (SUCRA score 80.1%), while CRE excelled in CMJ advancements (SUCRA score 93.4%), and the CRED group (alternating ET and RT) led in VOmax improvements (SUCRA score 81.6%). Furthermore, high-intensity interval training (HIIT) significantly enhanced VOmax compared to team sports. This meta-analysis emphasizes the effectiveness of CT in improving muscle power and VOmax in children and adolescents, surpassing isolated ET or RT, and advocates for integrating ET and RT to optimize physical performance. Future research should explore the mechanisms underlying these enhancements. Trial Registration: PROSPERO registration number CRD42022368452.

Consumer-grade optical heart rate (HR) sensors emerged as promising tools to monitor volume and intensity of physical activity (PA). However, no validation study of optical HR sensors included recent comprehensive validation recommendations, required for facilitating usage for medical purposes. Validity of HR data measured with four consumer-grade optical sensors, the wrist-worn Garmin Venu 2S and Polar Vantage M2, and the upper arm-worn Polar Verity Sense and Scosche Rhythm24 were assessed in 32 participants over 24 h including various laboratory-based and free-living activities. Furthermore, validity of time at moderate or vigorous PA intensity zones was analyzed. A medical-grade ECG served as a reference. Reliability was assessed by analyzing data of laboratory-based activities during two visits. Across activities, the mean absolute percentage error ranged from 2.2% to 4.7% and intraclass correlation coefficients ranged from 0.91 to 0.98, indicating high validity for all optical sensors. All sensors validly detected time spent at moderate or vigorous intensities (mean error < 10%), except Polar M2 for moderate PA (mean error 12.8%) and Garmin V2 for vigorous PA (mean error -15.9%). Sensor day-to-day reliability was high, indicated by a mean absolute error of < 5 beats/min. Upper arm-worn sensors consistently outperformed wrist-worn sensors, particularly in activities involving increased arm movement and at higher intensities. Our findings identified an overall high validity of these four consumer-grade optical HR sensors, also for assessing time spent at higher PA intensities. However, differences were observed between sensors regarding activity subtypes and intensity levels. These data support informed decisions when selecting optical sensors for PA monitoring and intervention. Trial Registration: The study was performed in compliance with the Declaration of Helsinki and its current amendments and was prospectively registered at ClinicalTrials.gov (ID NCT05525000).

Children and adults may react differently to warm-up preservation due to different physical characteristics. This study aimed to: (i) assess the impact of different rewarm-up routines in swimmers during a transition phase (20-25 min), including passive rest (SWU) or dynamic activities (RWU), on countermovement jump and swimming start performances, and (ii) explore potential RWU adaptations considering maturity offset (peak height velocity-PHV) and sex. Performance was analyzed using mixed effect ANCOVA, considering protocol, maturity offset (pre-PHV, mid-PHV, post-PHV, and adv. post-PHV), and sex. Results favored RWU over SWU with substantial magnitudes for jump height: pre-PHV (min-20, ES = 1.21; min-25, ES = 1.65), mid-PHV (min-20, ES = 1.23; min-25, ES = 1.14), post-PHV (min-20, ES = 1.37; min-25, ES = 0.73), and adv. post-PHV (min-20, ES = 1.03; min-25, ES = 0.65). Significant interactions at 25 min (p = 0.033, 0.047) showed that RWU outperformed SWU, especially in younger groups (pre-PHV, mid-PHV). RWU was superior to SWU for the reactive strength index at 20 min (p = 0.042) and 25 min (p = 0.047), with females having lower RSI than males at 20 min (p = 0.008, p = 0.015) and 25 min (p = 0.049) in later developmental stages. The flight distance (p = 0.009) and horizontal hip velocity (p = 0.014) revealed significant three-way interactions, with the male adv. post-PHV group responding better to RWU. Knee angular velocity was also higher after RWU, with male adv. post-PHV group showing more pronounced improvements (p = 0.016). These results suggest that though RWU had higher influence in male adults, it is a valuable approach for varying ages athletes.

Magnetic resonance imaging (MRI) is the gold standard for measuring muscle size. However, postural conditions for thigh musculature have not been standardized across studies, with some employing supine or prone positions and the thigh either placed on the examination table or suspended to avoid contact. In either case, the thigh is compressed or sagged by gravity, potentially affecting muscle size. This study aimed to examine the effects of postural conditions on thigh muscle size. Twenty Olympic-style weightlifters and 20 untrained controls (10 men and 10 women in each group) underwent 3-Tesla MRI in the supine and prone positions, with the thigh in compressed and suspended conditions to determine the maximal anatomical cross-sectional area (ACSAmax) and muscle volume of 15 thigh muscle groups/individual muscles. Postural conditions changed the ACSAmax of the quadriceps (range of postural-related changes: 1.0%-7.9%), hamstrings (0.8%-19.1%), and adductors (2.4%-19.2%). Regardless of measurement position, the total volume of thigh muscles decreased under compressed conditions (0.6%-3.8%). Quadriceps and adductors decreased in muscle volume under compressed conditions (0.9%-4.0% and 0.8%-6.6%), while hamstrings increased (1.4%-9.3%). Male weightlifters, who possessed the largest thigh muscle volume, showed greater postural-related changes in the muscle volume of quadriceps, hamstrings, and adductors than the other subgroups. Therefore, postural conditions during MRI substantially change thigh muscle size, and the magnitude of the change depends on muscle size. Our results provide in vivo evidence of the compressive behavior of thigh muscles and a new technical perspective for assessing thigh muscle size.

The U.S. National Health and Nutrition Examination Survey (NHANES) physical activity monitor datasets for 2011-12 and 2013-14 were released in late 2020. To date, there has been limited interpretation of these nationally representative wrist-worn accelerometer data (summarized and reported in Monitor Independent Movement Summary [MIMS] units) and their relationships with health-related outcomes. This study examined the associations between free-living Daily (volume), Peak 1 and Peak 30 (intensity), and risk of Metabolic Syndrome (MetS). Data from adults (N=3787; 18-80+ years) in the 2011-12 and 2013-14 NHANES cycles with health examination and accelerometry data were included. Accelerometer data were processed into Peak 1 and Peak 30 (MIMS/min), and Daily (MIMS/day). Design-based generalized linear and logistic regressions, and a sample-weighted decision tree, were used to examine associations between MIMS variables and MetS risk factors. Lower Peak 1, Peak 30 and Daily were observed for every one-unit increase in the number of risk factors -3.9 [95% CI: -4.3, -3.4] and -2.3 [-2.6, -2.1] MIMS/min, (-672.1 [-772.7, -571.5] MIMS/day, respectively, all p< 0.001). The Decision Tree classified individuals ≥ 46.5 years with a Daily ≥ 12 245 MIMS/day and a Peak 30 < 45.1 MIMS/min as having MetS (≥ 3 risk factors). Individuals < 46.5 years with a Peak 1 ≥ 62.9 MIMS/min were classified with 0 risk factors. Higher Daily and Peak were associated with an absence of MetS risk factors, with a progressive decline as the number of risk factors increased. These findings may be considered as preliminary benchmarks for Daily and Peak associated with cardiometabolic risk.

The application of force is a key aspect of performance during athletic activities. In jumping, the timing and magnitude of force application are important performance factors. The relative timing of forces has only been investigated in the countermovement jump. This study aimed to explore if the synchronization of peak concentric force with the instance of zero velocity during a drop jump impacted performance and examine the relationship of force-time curve shape to performance. Sixty-six state-level athletes (24 males and 42 females) completed drop jumps from a 30 cm box onto dual force plates. The jump with the highest reactive strength index (RSI) score was taken for analysis and classified as synchronous or asynchronous based on the relative timing of peak concentric force and zero velocity. RSI and other force-time variables were compared between groups, and functional principal component analysis (fPCA) was performed on the force-time curves, which were used to perform functional principal component regression (fPCR). Synchronous jumpers exhibited greater RSI scores and shorter contact times compared to asynchronous jumpers. Performance differences were largely driven by improved concentric kinetics, which the fPCR model revealed to have the greatest influence on RSI. Sex was also found to be a significant factor for RSI in the fPCR model. fPCA revealed that greater force application preceding and throughout the amortization phase was positively associated with RSI. The timing of peak concentric force and the shape of the force-time curve are key factors for drop jump performance, and these concepts should be investigated further in other athletic activities.

The ability to accelerate and attain high velocities is essential for both individual and team sport athletes. The purpose of this explorative study was to retrospectively analyze the ground reaction force using Statistical Parametric Mapping (SPM) vector field analysis, as traditional scalar analyses often fail to acknowledge the interdependence of force vector components. The ground reaction force vector and the scalar components (i.e., vertical and horizontal force) were analyzed for 28 male sprinters and 24 male soccer players at 8.0 and 8.5 m·s, and between 85%, 90%, 95%, and 100% of their maximum velocity. The ground reaction force vector differed predominately during mid-stance and late stance between both groups at 8.0 and 8.5 m·s. Within-group analysis also revealed that in both groups, the first ~60% of stance tended to increase in relevance when transitioning to higher sprinting velocities as evident by the increasing {T} test statistic between adjacent velocity comparisons. Sprinters and soccer player reached their respective maximal sprinting velocity at ~40 m. This exploratory study discusses the potential limitations of scalar analysis and highlights the benefits of incorporating vector field analysis. Although both analysis methods resulted in similar conclusions in our re-analysis, vector field analysis may still enhance the understanding of force application in sprint performance by considering the interdependence of force components. We recommend utilizing vector field analyses alongside traditional methods in sports biomechanics research to ultimately enhance the accuracy of interpretations related to vector data.

Previous findings of sex-differences in type, location, consequences, and risk factors of running-related injuries (RRIs) are contradictory. We aim to clarify these potential sex-differences. This cohort study analyzed prospective RRIs among recreational runners participating in running events (5-42 km) by combining data of two RCTs, including all intervention arms. Participants received a baseline questionnaire at registration and three follow-up questionnaires (before and up to 1 month after the event) detailing runners characteristics, injury characteristics (location, type [muscle and tendon], joint injury, etc.), and consequences (medication use, pain scores [0-10]). A predetermined injury definition was used to register RRIs. Data analysis was performed using descriptive statistics and univariate and multivariable logistic regression analysis of risk factors for a new RRI (demographics, training characteristics, event distance, and RRI-history), using separate models per sex. We analyzed 6428 participants with an average follow-up time of 4.8 months, 82% finished at least one follow-up questionnaire. During follow-up, 2133 (33%) participants (33% men, 34% women) suffered one or more RRIs. We found no sex-differences in injury location and type of injury. Men used less medication (13% vs. 15%, p = 0.01) and had lower pain scores while running (4.2 [SD2.9] vs. 4.5 [SD 2.8], p = 0.04) compared to women. A history of RRIs was associated with a new RRI in both men (OR 1.9 [95% CI: 1.6-2.2]) and women (OR 1.7 [95% CI: 1.4-2.0]). No relevant sex-differences were found between middle-aged runners. Our findings do not support accounting for sex-specific factors, specifically with regard to training characteristics, injury history, or injury consequences, in the development of personalized RRI risk reduction. Trial Registration: The INSPIRE trial (NTR5998) and SPRINT study (NL7694) were prospectively registered in the Dutch Trial Register.

The trial aimed to examine the effect of eight weeks preoperative low-load blood flow restricted resistance training (BFR-RT) on physical function, lower limb strength, and patient-reported outcomes in knee OA patients 3 and 12 months after total knee arthroplasty (TKA) compared with preoperative usual care. An assessor blinded randomized controlled trial (RCT) was conducted. Eighty-six patients scheduled for TKA who were allocated to 8 weeks BFR-RT on the affected leg 3x/week or preoperative usual care involving no exercise (CON).

Sedentary behavior (SB) may affect arterial stiffness, preceding the development of cardiovascular disease. We investigated the association of objectively measured SB with arterial stiffness. We also investigated factors that affected this association. We recruited adult volunteers and measured SB with thigh-worn accelerometery for 24 hrs/day for eight consecutive days. Central (carotid-femoral pulse wave velocity, cfPWV, gold standard) and local carotid arterial stiffness (stiffness index Beta and pressure-strain elasticity E) were measured with ultrasound. Linear regression was used and adjusted for demographics, cardiometabolic factors, and moderate-to-vigorous physical activity (MVPA) volume. Effect modification was studied with interaction terms. Participants (N = 664, 64 (standard deviation: 11, range: 23-89) years, 397 (59.8%) male) demonstrated 9.1 (1.6) hrs/day of SB, and arterial stiffness was 8.6 (3.0) m/s for cfPWV, 6.4 (2.9) for Beta, and 87 (43) kPa for E. SB was not associated with cfPWV (β = 0.04 95% CI (-0.11, 0.18), p = 0.60). The association of SB with local arterial stiffness was modified by systolic blood pressure (SBP) and MVPA volume. Stratified analyses revealed positive associations of SB with Beta (β = 0.29 (0.05, 0.53), p = 0.016) and E (β = 4.83 (1.39, 8.27), p = 0.006) in participants with SBP > 134 mmHg or > 103 min/day of MVPA (β = 0.23 (0.03, 0.42), p = 0.024 and β = 3.55 (0.82, 6.29), p = 0.011, respectively). We found no association of objectively measured SB with central arterial stiffness. However, SB was positively associated with local carotid stiffness in participants with higher SBP or MVPA levels. In certain subgroups, SB may affect carotid arterial stiffening, reinforcing the relation between SB and cardiovascular disease.

Running economy is an important determinant of endurance running performance, yet insights into characteristics contributing to its inter-individual variability remain limited. Although slow-twitch muscle fibers are more energy-efficient than fast-twitch fibers during the (near-)isometric contractions common during submaximal running, current literature lacks a consensus on whether a relationship between muscle fiber-type distribution and running economy exists. This study aims to resolve the ongoing debate by addressing potential confounding factors often overlooked in prior research, such as the effect of different running speeds, the homogeneity of investigated groups, and the potential impact of the adopted running gait. We selected two groups with predetermined distinct muscle fiber-type distribution in their triceps surae muscle by measurement of carnosine via H-MRS, one predominantly slow (ST; n = 11; carnosine z-score = -1.31) and the other predominantly fast (FT; n = 10; z-score = 0.83). Across a range of running speeds (2-4 m/s), we measured running economy (W/kg) through indirect calorimetry, along with running kinematics, kinetics and muscle activity of the lower limb. The ST-group exhibited, on average, 7.8% better running economy than the FT-group (p = 0.01) and this difference was consistent across speeds. Both groups demonstrated almost identical kinematics, kinetics, and muscle activity patterns across submaximal running speeds. Overall, our findings indicate that distinct muscle fiber-type distribution explains some of the observed variability in running economy, for which a predominance of energy-efficient slow-twitch fibers appear beneficial. In contrast, muscle fiber-type distribution does not affect running gait substantially.

To investigate the effect of moderate or heavy slow resistance training on structural and mechanical properties of patellar and Achilles tendons in older men, in vivo. Healthy older men (n = 27) undertook a 12-week resistance training program (3 times/week) of triceps surae and quadriceps muscle-tendon complexes. Participants were randomly assigned to either a moderate load of 55% 1RM (O55, n = 13, age: 70.0 ± 4.6 years) or a progressively heavier load from 55% up to 80% 1RM (O80, n = 14, age: 69.8 ± 4.4 years). Tendon morphology was investigated using a 1.5 T MRI scanner. Mechanical properties of the free Achilles tendon (AT) and medial gastrocnemius (MG) aponeurosis, patellar tendon (PT), and deep aponeurosis of the vastus lateralis (VL) muscle were assessed using ultrasound imaging. Both training programs led to an increase in mean CSA of the PT (O55; +2.7%, O80; +1.7%, p = 0.002) and AT (O55; +2.8%, O80; +2.5%, p < 0.001). Force and stress were increased for all the four regions investigated, while stiffness and Young's modulus assessed at a common force level were only increased for the AT and VL aponeurosis. No interaction between group and time was demonstrated for any of the outcomes. No interaction between time and the four tendon sites was observed for any of the outcomes at common force. A supervised short-term heavy or moderate slow resistance training of equal volume yielded an increase in tendon size and altered mechanical properties of tendinous tissue.

The aim of this study was to investigate the difference in head acceleration event (HAE) incidence between training and match-play in women's and men's players competing at the highest level of domestic rugby union globally. Players from Women's (Premiership Women's Rugby, Farah Palmer Cup) and Men's (Premiership Rugby, Currie Cup) rugby union competitions wore instrumented mouthguards during matches and training sessions during the 2022/2023 seasons. Peak linear (PLA) and angular (PAA) acceleration were calculated from each HAE and included within generalized linear mixed-effects models. The incidence of HAEs was significantly greater in match-play compared to training for all magnitude thresholds in both forwards and backs, despite players spending approximately 1.75-2.5 times more time in training. For all HAEs (PLA > 5 g and PAA > 400 rad/s), incidence rate ratios (IRRs) for match versus training ranged from 2.80 (95% CI: 2.38-3.30; men's forwards) to 4.00 (3.31-4.84; women's forwards). At higher magnitude thresholds (PLA > 25 g; PAA > 2000 rad/s), IRRs ranged from 3.64 (2.02-6.55; PAA > 2000 rad/s in men's backs) to 11.70 (6.50-21.08; PAA > 2000 rad/s in women's forwards). Similar trends were observed in each competition. Players experienced significantly more HAEs during match-play than training, particularly at higher magnitude thresholds. Where feasible, HAE mitigation strategies may have more scope for HAE reduction if targeted at match-play, particularly where higher magnitude HAEs are the primary concern. However, the number of HAEs associated with different training drills requires exploration to understand if HAEs can be reduced in training, alongside optimizing match performance (e.g., enhancing contact technique).

The aim of the study is to investigate the association of cardiorespiratory fitness (CRF) and muscular strength indicators with gray matter volume (GMV) and to study whether fitness-related regions of GMV are associated to executive function (EF) in cognitively normal older adults. Ninety-one cognitively normal older adults (71.69 ± 3.91 years; 57.14% females) participated in this study from the AGUEDA trial. CRF was measured by a 2-km walking test and a 6-min walking test. Muscular strength was measured by handgrip, biceps curl, squats, and isokinetic strength tests. T1-weigthed images were obtained through a magnetic resonance scan. GMV was determined by voxel-based morphometric analysis. Standardized EF tests were performed. CRF did not show any positive association with GMV. Handgrip strength was positively associated with GMV (p < 0.001) in nine regions (β from 0.6 to 0.8 and k from 106 to 1927) and knee extension strength in three regions (β from 0.4 to 0.5 and k from 76 to 2776). Squats strength was negatively associated with GMV (p < 0.001) in two regions (β = -0.3, k = 1102 and k = 152) and the 2-km walking test in one region (β = -0.4, k = 99). Only handgrip strength-related GMV was associated with cognitive flexibility (p = 0.039, β = 0.215) and spatial working memory (p < 0.03, β 0.247-0.317), but not with EF score (p > 0.05). Muscular strength, but no CRF, may be positively related to GMV in cortical and subcortical regions, with implications for specific cognitive domains rather than the overall EF score. Specifically, handgrip strength was the indicator most associated with higher GMV, while squats strength and CRF were negatively related to GMV. ClinicalTrials.gov identifier: NCT05186090.

Competitive swimmers complete 50-m front crawl swimming without breathing or with a limited number of breaths. Breath holding during exercise can trigger diving reflex including bradycardia and diminished active muscle blood flow, whereas oxygen supply to vital organ such as brain is maintained. We hypothesized that swimmers achieving faster time in 50-m front crawl with limited number of breaths demonstrate a blunted diving reflex of cardiac and active muscle blood flow responses with elevated cerebral perfusion to counteract peripheral and central fatigues. Twenty-eight competitive swimmers (12 females) underwent a 50-m front crawl swimming time trial with minimum respiratory interruptions, following which they were categorized into two groups: Fast (n = 13) and Slow (n = 15). Additionally, they performed knee extension exercises with maximal voluntary breath- holding, wherein leg blood flow (Doppler ultrasound), cardiac output (Modelflow), heart rate (electrocardiogram), and middle cerebral artery mean blood velocity (transcranial Doppler ultrasound) were evaluated. The pattern of leg blood flow response differed between the two groups (p = 0.031) with the Fast group experiencing a delayed onset of reductions in leg blood flow (p = 0.035). The onset of bradycardia was also delayed in the Fast group (p = 0.014), with this group demonstrating a higher value of the lowest heart rate (between-trial difference in average: 15.9 [3.73, 28.2] beats/min) and cardiac output (between-trial difference in median: 2.84 L/min) (both, p ≤ 0.013). Middle cerebral artery mean blood velocity was similar between the groups (all p ≥ 0.112). We show that swimmers with superior performance in 50-m front crawl swim with limited breaths display a diminished diving reflex.