BACKGROUND:Musculoskeletal injuries (MSKIs) pose a major threat to military readiness, affecting nearly 40% of personnel annually, driving over 5 million medical visits and 24 million limited duty days. Validated methods for identifying and preventing injuries are a priority for the Department of Defense. PURPOSE:To externally validate a previously developed prediction model for identifying MSKI risk in a U.S. Army airborne infantry brigade. STUDY DESIGN:Prospective cohort; model validation study. METHODS:U.S. Army paratroopers newly assigned to the 173rd Airborne Brigade (Nov 2022-Aug 2023) underwent baseline screening with a published risk prediction algorithm. The primary outcome was a duty-limiting MSKI within one year, identified through the Army's e-Profile database from the Medical Operations Data System. Model performance was assessed for discrimination, calibration, calibration-in-the-large, overall fit, and decision curve analysis, with internal validation using 2,000 bootstrap interactions. Performance was compared with the original model. RESULTS:308 paratroopers were prospectively followed for one year (93,636 military exposure days), during which 30.7% sustained a duty-limiting musculoskeletal injury. The model demonstrated poor discrimination (AUC 0.59, 95% CI 0.52-0.66) and only marginal net benefit over a treat-all strategy. CONCLUSIONS:The model failed to discriminate injury risk (AUC 0.59) and did not provide reliable calibration or meaningful net benefit. This model does not justify implementation for injury risk screening in this specific setting.
BACKGROUND:Hip and pelvic bone stress injuries (BSIs) represent a small but clinically significant subset of overuse injuries sustained during U.S. Army Basic Combat Training (BCT). However, the long-term military service and healthcare implications remain unclear. This study examined the impact of hip and pelvic BSIs sustained during BCT on subsequent military career outcomes and musculoskeletal healthcare utilization. METHODS:In this case-control study, BCT graduates from fiscal years 2015 to 2017 were analyzed. Cases included 895 BCT graduates with MRI-confirmed hip or pelvic BSI, representing 63.6% of all BSI-diagnosed trainees; controls (n=2,685) were BCT graduates without BSI, matched 3:1 by age and sex. Adjusted logistic regression models evaluated differences in Advanced Individual Training (AIT) graduation, service retention, and satisfactory completion of obligated service. Time-to-discharge was analyzed using Cox proportional hazards models, and annual musculoskeletal healthcare encounters were compared using negative binomial regression. RESULTS:Compared with controls, trainees with MRI-confirmed hip and pelvic BSIs had significantly worse career and healthcare outcomes. BSI cases had significantly lower odds of graduating from AIT (OR = 0.27, 95% CI: 0.18-0.41) and lower odds of satisfactory completion of obligated service (OR = 0.62, 95% CI: 0.48-0.79) compared to controls. BSI cases had a higher risk of early discharge (HR = 1.44, 95% CI: 1.30-1.60). Female cases demonstrated higher attrition and lower graduation rates than males. Musculoskeletal healthcare utilization was 2.6 times higher among BSI cases during the first post-BCT year (RR = 2.61, 95% CI: 2.31-2.96) and remained elevated through year three. CONCLUSIONS:Trainees who sustain hip or pelvic BSIs during BCT experience lasting negative impacts on military retention and healthcare utilization, despite successfully graduating from BCT. These injuries impose a disproportionate long-term burden, particularly among female trainees. Targeted prevention and comprehensive rehabilitation strategies are essential to mitigate their career and readiness impacts.
PURPOSE:To examine the effects of exercise timing (morning [AX] vs evening [PX]) on functional capacity, psychological outcomes, and sleep-related measures in cancer patients undergoing treatment. METHODS:Forty-four cancer patients undergoing treatment participated in a supervised exercise intervention at the University of Northern Colorado Cancer Rehabilitation Institute (UNCCRI). Participants self-selected exercise timing as AX (0700-0900) or PX (1600-1800) and completed a range of pre- and post-intervention physical and psychological assessments. A subset of participants (n=24) completed objective sleep and recovery monitoring using a wearable tracker. RESULTS:Both AX and PX groups demonstrated significant improvements in functional capacity, with no significant differences between groups for these variables (p > 0.05). In contrast, exercise timing was associated with significant differences in psychological and autonomic outcomes. The AX group demonstrated greater reductions in Beck Depression scores (-4.86 ± 5.72 vs -1.02 ± 4.48; p < 0.05) and greater improvements in PSQI scores (-3.76 ± 3.39 vs 0.08 ± 1.83; p < 0.001) compared to the PX group. The AX group exhibited a substantially greater increase in heart rate variability (8.01 ± 6.31 ms) compared to a decrease in the PX group (-4.49 ± 6.79 ms; p < 0.001), representing a marked divergence in autonomic adaptation between groups. These differences were supported by moderate-to-large to very large effect sizes, indicating clinically relevant improvements in autonomic and psychological outcomes. No other objective sleep variables differed significantly between groups. CONCLUSIONS:A 12-week supervised exercise intervention improved functional capacity in cancer patients undergoing treatment, independent of exercise timing. However, morning exercise was associated with greater improvements in autonomic function, sleep quality, and depressive symptoms compared to afternoon/evening exercise.
PURPOSE:The relationship between exercise and brain function has been studied extensively; however, whether different exercise modalities promote hippocampal neurogenesis and cognitive function through shared or distinct biological pathways remains unclear. This study examined the effects of endurance training (ET), resistance training (RT), and high-intensity interval training (HIIT) on hippocampal neurogenesis, spatial memory, and neurotrophic factors. METHODS:Forty 3-month-old male C57BL/6J mice were randomized to control (SED), ET, RT, or HIIT groups. Following the training intervention, adult hippocampal neurogenesis was assessed in the dentate gyrus using BrdU⁺/NeuN⁺ immunolabeling. Hippocampal measures of neurotrophic factors, including brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), and fibronectin type III domain-containing protein (FNDC5), were quantified. Spatial memory was evaluated using the Barnes maze. RESULTS:All exercise modalities increased the number of BrdU⁺/NeuN⁺ cells compared with sedentary controls (RT, p<0.001; ET, p=0.001; HIIT, p=0.016). Each modality produced a distinct molecular profile. RT elicited the greatest increases in hippocampal BDNF compared to all groups (RT vs. ET, p=0.007; RT vs. HIIT, p<0.001; RT vs. SED, p<0.001) and increased IGF-1 levels (RT vs. SED, p=0.014). ET increased hippocampal FDNC5 (ET vs. SED, p=0.033), whereas HIIT did not alter measured neurotrophic or myokine levels. Only RT and ET improved spatial learning. CONCLUSIONS:Although all exercise modalities increased hippocampal neurogenesis, only those associated with elevations in neurotrophic factors demonstrated improvements in spatial learning. These findings suggest that different exercise modalities may promote hippocampal plasticity through distinct biological profiles and that increases in neurogenesis alone may not be sufficient to enhance cognitive function.
PURPOSE:To compare changes in running biomechanics between two gait modifications: cues to run softly and quietly (SOF) and shifting to a forefoot strike pattern (FFS). METHODS:Thirty-eight individuals completed testing, including running with habitual gait (HAB) and the two gait modifications, while biomechanical data were collected. Variables of interest included joint angles and moments, knee stiffness, and ground reaction forces. Repeated measures analysis of variance was used to compare gait conditions. RESULTS:The SOF condition showed higher peak knee flexion angles and excursion, foot strike angles (vs. HAB and FFS), and higher peak and initial contact ankle dorsiflexion angles, peak eversion angles, and lower initial contact ankle inversion angles (vs. FFS). The FFS condition resulted in a more plantarflexed and inverted ankle at initial contact, as well as a more plantarflexed foot. The SOF condition resulted in reduced peaks and loading rates for vertical and posterior forces, however FFS led to reduced vertical loading rates compared to HAB and SOF. For joint moments, the SOF condition showed increased hip flexion and extension moments and reduced knee stiffness (vs. HAB and FFS), and reduced ankle plantarflexion moments (vs. FFS). The FFS condition also showed increased knee flexion and ankle plantarflexion moments compared to HAB. CONCLUSIONS:The SOF modification was shown to be a viable alternative to FFS for reducing several key aspects of biomechanical loading during running, including sagittal knee and ankle moments and knee stiffness, as well as peaks and loading rates for vertical and posterior ground reaction forces. However, the increases in hip joint moments should lead to some caution and warrant further investigation.
PURPOSE:Although perceptual scales are widely used to prescribe endurance training, whether aerobic training status influences perceptual responses to heavy-intensity exercise remains unclear. Thus, this study investigated the effects of aerobic training status on perceptual responses during cycling performed at the maximal metabolic steady state (MMSS). METHODS:Thirty-two participants (untrained, n = 18; trained, n =14) performed:1) step-ramp-step to determine maximal oxygen uptake (V̇O2max) and, 2) MMSS estimated intensity, followed by at least two 30 min constant workload rides to confirm the MMSS. The MMSS was defined as the highest exercise intensity at which oxygen uptake and blood lactate concentration were stable between the 15 th and 30 th min of exercise (change <120 mL·min -1 and <1 mmol·L -1, respectively). During the MMSS ride, rating of perceived exertion (RPE, 6-20), fatigue, leg pain, and dyspnea scales (0-10) were recorded at baseline and every 5 min until the end of exercise. RESULTS:V̇O2max (36.2 ± 6.6 mL·kg -1·min -1) and MMSS intensity (134 ± 40 W) were lower in untrained than trained group (V̇O2max: 54.0 ± 3.4 mL·kg -1·min -1; MMSS intensity: 209 ± 46 W) (p<0.001). Group×time interactions were observed for RPE (p≤0.001), fatigue (p=0.003), leg pain (p=0.009), and dyspnea (p=0.0018).Compared with the trained, the untrained group reported higher fatigue from 15 to 30 min (Δ= 2 a.u vs 1 a.u) and higher RPE (Δ= 2 a.u vs 1 a.u), leg pain (Δ= 2 a.u vs 1 a.u), and dyspnea from 20 to 30 min (Δ= 2 a.u vs 1 a.u) (post hoc p ≤0.04). CONCLUSIONS:Training status modulates the time course of perceptual drift at MMSS, with higher perceptual responses in untrained than trained individuals. Between-group differences emerged around 15 min, highlighting the importance of considering exercise duration when using perceptual scales to guide exercise at MMSS.
PURPOSE:This study aimed to develop and validate Elastic Net-based predictive models using simple anthropometric measurements to estimate dual-energy X-ray absorptiometry (DXA)-derived body composition variables in older women. METHODS:Body mass, skinfolds, circumferences, and DXA measures of total and regional fat mass (FM) and lean soft tissue (LST) were obtained from 523 older women. Elastic Net regression developed models for total body, upper- and lower-limb FM and LST, and android and gynoid FM. The sample was split into training, validation, and independent testing sets. RESULTS:Elastic Net models demonstrated high predictive accuracy for DXA-derived body composition. Coefficients of determination were strong for total FM and LST (R² ≥ 0.884), and good for regional compartments (R²≥ 0.711). Root mean square errors were low across outcomes (0.272-1.858 kg). Bland-Altman analyses showed minimal mean bias for most variables, except for lower-limb FM and android FM, which presented small but significant biases (≤ 2.78 %). Proportional bias was identified in some models, although the explained variance remained low (≤22%). Limits of agreement were narrow for total body estimates (≤11.73%), while wider limits were observed for segmental measures. CONCLUSIONS:Elastic Net-based models provide accurate estimates of total body composition and acceptable estimates of regional compartments, although regional predictions showed greater individual variability than total body estimates. However, these prediction equations should be interpreted as internally validated models intended primarily for screening and research applications.
OBJECTIVES:Assess differences in lower limb strength between adolescents with and without patellofemoral pain (PFP) and explore the association between strength and pain in adolescents with PFP. DESIGN:Cross-sectional. METHODS:One hundred and two male and female (n=24) adolescents aged 12-19 (mean=17 years ± 2) participated in this cross-sectional study (n=51 with PFP and n=51 age- and sex-matched controls). Strength was measured as peak isometric torque (Nm) using an isokinetic dynamometer during knee extension/flexion, and ankle plantar flexion. The worst pain in the previous week was rated on an 11-point numerical rating scale (0=no pain, 10=worst pain imaginable). Differences in strength between participants with and without PFP, as well as associations between strength measures and pain in adolescents with PFP, were investigated using separate linear regression models, unadjusted and adjusted for age, sex, and body weight. RESULTS:Adjusted mean (95% confidence interval [CI]) knee extension strength was 18.2 (3.6-32.8)Nm less in adolescents with PFP than in controls. For every one-point increase in pain, there was a mean (95% CI) adjusted reduction of 8.0 (15.4-0.6)Nm and an unadjusted reduction of 12.6 (23.5-1.7)Nm of knee extension torque in the PFP group. There were no between-group differences or associations between strength and pain for the other strength measures. CONCLUSIONS:Adolescents with PFP may have lower knee extension strength than their pain-free counterparts. Higher pain may be associated with lower knee extension strength in adolescents with PFP. Future research may investigate whether increases in knee extension strength in adolescent PFP mediate improvements in pain.
INTRODUCTION:Caffeine is well recognized to acutely enhance repeated sprint performance during intermittent exercise involving brief, repeated efforts. However, it remains unclear whether a single pre-exercise dose improves repeated sprint performance, and whether it alters noradrenergic, cardiorespiratory, and perceptual responses over several hours. METHODS:12 healthy young adults (4 females) completed two randomized, double-blind trials ingesting caffeine (5.5 mg·kg⁻¹) or placebo. Approximately 60 min after ingestion, participants performed three repeated sprint sets over a 3.5 h protocol. Each set consisted of 5 min of moderate-intensity cycling followed by 6 × 5 s sprints. Plasma samples were collected for caffeine and noradrenaline concentration analysis. Ratings of perceived exertion (RPE), leg muscle pain, respiratory variables, and heart rate were recorded. Middle cerebral artery mean blood velocity (MCAVmean), an index of cerebral blood flow, was measured using transcranial Doppler, and carotid artery blood flow was assessed using ultrasound. RESULTS:Caffeine increased mean sprint power across repeated sprint sets compared with placebo (P < 0.05), with modest but consistent effects sustained up to 3.5 h post-ingestion (0.5-2.4%). Peak power was also enhanced in the second and third sets, with increases of up to 3.7% (P < 0.05). These effects were accompanied by higher plasma noradrenaline concentrations (P < 0.05) and lower RPE and leg muscle pain (P < 0.05). Caffeine also reduced partial pressure of end-tidal CO2 and MCAVmean, and increased heart rate (P < 0.05). CONCLUSIONS:A single pre-exercise dose of caffeine (5.5 mg·kg⁻¹) sustains ergogenic effects across multiple repeated sprint bouts over 3.5 h post-ingestion. These improvements were observed alongside increased noradrenergic activity, reduced perceptual strain, and concomitant cardiorespiratory responses.
PURPOSE:The world's fastest vertical kilometer course in Fully (Switzerland) is comprised of stairs at a very steep grade (~31°). The aim was to determine whether stair ascent, with and without poles, lowered physiological, mechanical, and neuromuscular demands compared with continuous uphill ramp locomotion at VK-relevant slopes. METHODS:Twenty-two endurance-trained participants completed randomized treadmill trials at a constant vertical speed (800 m·h-1) in three conditions: uphill ramp (R), stairs (S), and stairs with poles (SP), each performed at six slopes (18-38°). Metabolic power (MP), heart rate (HR), minute ventilation (V̇E), rating of perceived exertion (RPE), internal mechanical work, step frequency, and lower-limb electromyography were measured. RESULTS:At 18°, S elicited greater MP (6%), HR (4%), and V̇E (7%) compared to R (all P<0.001), with no difference in RPE. From 26° to 38°, S elicited less MP (6-10%), HR (5-10%), V̇E, and RPE relative to R (all P≤0.05). Across 26-38°, S involved less internal mechanical work (23-45%, P<0.001), lower step frequency (P<0.001), and reduced gastrocnemius lateralis activity (P<0.001) compared with R. Relative to S, SP reduced gastrocnemius lateralis and vastus lateralis activity (P<0.05) but did not change MP, HR, V̇E, or RPE (all p≥0.09). CONCLUSIONS:On very steep slopes, stairs improve uphill economy and reduce rate of perceived exertion, likely through reductions in internal mechanical work and plantar-flexor demand. These findings provide a mechanistic explanation for exceptional performances on VK courses featuring extended stair sections. Using poles on stairs altered the activation of the measured lower-limb muscles, particularly by reducing gastrocnemius lateralis activity, without clear physiological or perceptual benefit at the tested intensity.
Purpose: To examine the associations of physical activity (PA) and physical fitness with executive function among disabled children and adolescents, and explore potential differences across disability types and gender. Methods: Two hundred and forty-one participants (64.3% boys; mean age: 12.96 ± 3.29 years) with physical disabilities (PD, n = 112), intellectual disabilities (ID, n = 119), and hearing impairment (n = 10) were recruited from 19 special schools. PA was measured with wrist-worn accelerometers. Physical fitness, including body composition, muscular strength, muscular endurance, and flexibility, was assessed using the Brockport Physical Fitness Test. Executive function was evaluated through computer-based tasks that measured mean accuracy and reaction time. Results: Linear mixed models revealed that higher PA and better muscular fitness were positively associated with the accuracy of executive function tests. Both light PA (LPA, B = 0.03; 95% confidence intervals [CI]: 0.00, 0.06; d = 0.295) and moderate-to-vigorous PA (MVPA; B = 0.25; 95%CI: 0.14, 0.36; d = 0.611) showed significant associations with accuracy. Muscular fitness, including curl-ups ( B = 0.58; 95% CI: 0.16, 1.00; d = 0.285) and handgrip strength ( B = 0.74; 95% CI: 0.42, 1.07; d = 0.587), demonstrated positive associations with accuracy. Disability-specific analyses indicated that MVPA and handgrip strength were consistently associated with accuracy in both PD and ID groups, while PA was associated with reaction time only in the PD group. Gender-stratified analyses revealed that muscular fitness showed stronger associations with executive function in PD boys, whereas MVPA demonstrated stronger associations with accuracy in PD girls. Conclusions: Promoting PA and improving muscular fitness may enhance executive function in disabled children and adolescents, with patterns varying by disability type and gender. However, the cross-sectional design precludes causal inferences, and future longitudinal studies are needed to establish causality and explore potential mediating mechanisms.
PURPOSE:Greater moderate-to-vigorous physical activity (MVPA) and light physical activity (LPA), with lower sedentary behavior (SED) during pregnancy are associated with more favorable maternal-child health. There is limited research examining the co-occurrence of these behaviors and who may be at risk for less optimal activity patterns across pregnancy. This study identifies and examines predictors of distinct activity profiles across pregnancy. METHODS:The present study is a secondary analysis of the Pregnancy 24/7 prospective cohort study (n=470). Participants wore a thigh-mounted accelerometer for up to 7 full days in each trimester to measure waking minutes per day of SED, LPA, and MVPA. Latent profile analysis identified distinct longitudinal activity patterns across pregnancy. Stepwise multinomial logistic regression examined predictors of profile membership. RESULTS:Five latent profiles were identified: High Sedentary (22%), Mixed Sedentary (34%), Mixed Active (25%), and High LPA (7%), High MVPA (12%). Activity patterns were stable across trimesters but differed substantially between profiles. Living with one or more children under age 5 (Relative risk ratio [RRR]: 2.15-3.84) and standing or active occupations (RRR: 9.25-45.77) were associated with greater likelihood of belonging to Mixed Active or High LPA profiles. Pre-pregnancy body mass index ≥30 kg/m² was associated with lower likelihood of membership in all more active profiles, particularly High MVPA (RRR: 0.13), compared to High Sedentary. Multiparous individuals were more likely to belong to higher LPA profiles, whereas nulliparous individuals were more likely to exhibit higher MVPA. CONCLUSIONS:Distinct patterns of activity occur across pregnancy. Those without children under age 5, in sedentary occupations, and with pre-pregnancy BMI ≥30 kg/m 2 had less favorable patterns and may benefit from targeted physical activity interventions to promote maternal-child health.
PURPOSE:In young adults, performance fatigability is affected by sex even with minor power output (PO) changes around the maximal lactate steady-state (MLSS). This study investigated whether these sex- and intensity-dependent effects persisted in older adults. METHODS:9 females (65±5 yrs) and 10 males (67±4 yrs) performed three 30-min constant-PO exercise bouts at MLSS, 10 W below (MLSS-10), and 10 W above (MLSS+10), each followed by a time to task failure (TTF) test at 80% peak-PO. Performance fatigability was assessed via knee extensor isometric maximal voluntary contractions (IMVC), voluntary activation (VA), and potentiated 100 Hz doublet torque (Db100) before, immediately after the constant-PO and the TTF bouts. RESULTS:IMVC declined less after MLSS-10 (-18±8%) than MLSS+10 (-22±8%; p=0.04), but neither differed from MLSS (-20±8%). Similarly, Db100 decline was smaller at MLSS-10 (-14±6%) than MLSS+10 (-19±9%; p=0.03) but similar to MLSS (-15±0%). VA decreases were similar across all intensities (-6-7%; p>0.05). No sex differences were found for any fatigability variables (p>0.05). Despite the shorter TTF with increased in intensity at the end of each 30-min constant-PO (p<0.001), performance fatigability parameters at failure were similar across conditions (p>0.05), without sex-related differences. CONCLUSIONS:Unlike previous reports in younger populations, older males and females exhibited similar fatigability profiles after slight manipulations in PO around the MLSS, suggesting sex-based differences in muscular endurance diminish with age.
Introduction: Prolonged physical exertion in hot and/or humid environments can induce physiological strain and increase the risk of heat exhaustion or exertional heat stroke (EHS). Heat acclimatization (HA) optimizes an individual’s ability to tolerate heat and is therefore widely adopted to improve exercise performance in thermally challenging environments. Sweat is a key thermoregulatory indicator reflective of physiological adaptations during HA and hence is regarded as a valuable resource for monitoring HA. However, knowledge of molecular-level changes and adaptations in sweat associated with HA remain limited. Methods: We exploited a non-invasive proteomics-based approach for identifying HA-associated protein changes in sweat. Advanced mass spectrometry-based proteome profiling was performed on sweat samples obtained from forehead and chest, collected before and after two weeks of isothermic conditioning (pre-IC/post-IC). The IC program was designed to elevate and maintain core temperature (T c ) ≥ 38.5 ℃ through jogging and circuit activities, thereby enhancing the thermal stimulus to confer a favourable heat-adapted phenotype. Results: The sweat landscape revealed that HA profoundly modulated sweat protein compositions, with more pronounced effects post-thermal conditioning in forehead sweat compared to chest sweat. Functional correlation analysis of altered proteins indicated that heat adaptations involved close-knit crosstalk between proteins mediating heat response and immune-related proteins. We identified distinct-site specific alterations responsive to heat adaptation and observed that several of the top differentially expressed proteins post-IC were linked to immune processes such as B cell activation and interleukin signaling, and vasoregulation. Notably, proteins including IL1RA, UTS2, CALM1, and HPX showed consistent changes with thermoregulation across both sites, suggesting their potential to be explored as sweat-based biomarkers for monitoring individual responses to HA. Conclusions: Our findings demonstrate HA modulates sweat protein profiles in a site-specific manner and opens new avenues for exploring the utility of sweat-based protein markers for monitoring and evaluating heat acclimatization.
PURPOSE:To determine the criterion validity of research- and consumer-grade wearables (18 step-based methods) for quantifying step counts and step-derived walking metrics in free-living conditions. METHODS:Sixty healthy adults (20-80 years, balanced by sex and decade) wore six monitors for seven days: StepWatch (ankle), activPAL (thigh), ActiGraph (hip and wrist), Fitbit Inspire 2 (hip), Fitbit Charge 5 (wrist), and Garmin Vívoactive 4S (wrist), while wearing a waist-mounted video camera at their discretion during free-living sessions. Step counts from all devices were used to derive metrics of bout duration, frequency, and intensity. Raw ActiGraph data were also processed using five wrist-based machine-learning models for step detection. Video-identified steps labeled by trained researchers served as the criterion. Equivalence testing was performed using a ±10% equivalence margin. RESULTS:Fifty-six participants provided 150 hours of valid video and 10,194 walking bouts. Only StepWatch fell within the equivalence margin for step counts with a mean absolute percent error (MAPE) <10%, with seven additional methods at 10-20%. For total walking bout duration, only activPAL and ActiGraph wrist-StepCount met equivalence criteria; activPAL achieved MAPE <10% and five others at 10-20%. No method met equivalence for the number of walking bouts, with MAPE >20% and balanced accuracy in bout detection <50%. For time spent in moderate-to-vigorous physical activity, activPAL (18.6%) and StepWatch (16.2%) achieved MAPE <20%, but no methods met equivalence. CONCLUSIONS:The level of step-count accuracy obtained from wearable devices did not translate into a comparable level of accuracy in quantifying real-world walking activity. Overall, activPAL, StepWatch, ActiGraph hip/1s and ActiGraph wrist-StepCount showed the most consistent performance. These findings can help researchers select step-based methods that more accurately capture real-world walking patterns.
Introduction: Multidirectional sports introduce unique forces to the tibia that potentially induce more symmetrical distribution of bone mass and lower bone stress injury risk, when compared to unidirectional sports. Purpose: To compare tibial shaft size, shape, and estimated strength among competitive male and female athletes in sports with different loading demands. Methods: High-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the tibial diaphysis (30% site) were performed in 149 NCAA Division I male and female cross-country and basketball athletes, female gymnastics and lacrosse athletes, and male American football athletes playing the wide receiver position. Tibial shaft outcomes relating to bone shape (ratio of the maximum and minimum moments of area [Imax/Imin]), size, and strength were compared by sport within each sex. Bone size outcomes were scaled to bone length to adjust for allometry. Kruskal-Wallis tests estimated group differences. Results: In female athletes, gymnastics had a 13.5% lower Imax/Imin than cross-country (median [IQR] = 1.7 [1.4, 1.9] vs. 2.0 [1.8, 2.2], p =0.041) indicating a more symmetrical distribution of bone. In male athletes, football had the lowest Imax/Imin of all sports evaluated (median [IQR] = 1.6 [1.4, 1.8]), although this did not reach significance ( p =0.051). There were no differences in tibial shaft outcomes between female gymnastics athletes or male football athletes and sex-matched basketball athletes ( p >0.196). There were also no differences between female lacrosse and cross-country athletes ( p >0.500). Conclusions: The contributions of multidirectional sports on tibial shaft characteristics are nuanced, and high-impact loading may be necessary to develop a more symmetrical shape, which may influence tibial bone stress injury risk.
PURPOSE:Cardiorespiratory fitness (CRF) is an integrative measure of physiologic health, but how CRF relates to different body composition components and cardiometabolic health in community-dwelling adults remains uncertain, especially in obesity. METHODS:In Framingham Heart Study (FHS) Generation 3/Omni-2 participants, body composition measures from dual-energy X-ray absorptiometry (DXA) were related to peak oxygen uptake (VO2) and complementary exercise phenotypes assessed via cardiopulmonary exercise testing in sex-stratified multivariable linear models. Secondary analyses examined correlates of peak VO2 when indexed to total body weight or lean mass. RESULTS:Among 2647 participants (53% women, mean age 54 years, body mass index [BMI] 27.8 kg/m 2), lean mass was the strongest correlate of CRF among body composition measures (FDR <5%) and, along with age and height, accounted for 44-48% of the variance in peak VO2. A 1 kg-higher lean mass was associated with a 43 ml/min-higher absolute peak VO2. While there was broad consistency across age, sex-based differences in the relations of body composition and CRF were observed, with women demonstrating stronger positive associations between CRF and fat mass compared to men. Peak VO2 displayed distinct cardiometabolic correlates depending on whether it was indexed to total body weight versus lean mass: "metabolically healthy" obesity displayed lower peak VO2 compared to "metabolically healthy" non-obesity with indexing to total body weight, but peak VO2 was similar between these two categories with indexing to lean mass. CONCLUSIONS:Lean mass is the strongest correlate of CRF in middle-aged, community-dwelling individuals. Indexing peak VO2 to lean versus total mass results in different conclusions regarding the intersections of CRF with obesity and metabolic health and emphasizes the role of cardiometabolic risk factors beyond obesity itself.
PURPOSE:This study aimed to elucidate age-specific mechanical and physiological recovery kinetics following maximal eccentric exercise and evaluate the efficacy of force-plate-standardized foam rolling (FR) intervention in mitigating myofascial stiffening and systemic biomarker efflux across young and middle-aged populations. METHODS:Thirty-two physically active males were stratified into young (20-30 years) and middle-aged (40-55 years) groups. Using a randomized, counterbalanced crossover design, participants performed a high-volume, maximal eccentric knee protocol (20 sets, 236 total repetitions across varying velocities) followed by either passive recovery (control) or standardized FR. Mechanical properties via ultrasound shear wave elastography, systemic biomarkers, creatine kinase (CK) and lactate dehydrogenase (LDH), and perceived soreness were assessed at baseline, 0 h, 24 h, 48 h, and 72 h post-exercise. RESULTS:In control, both groups exhibited profound delayed-onset CK elevation peaking at 72 h. Counterintuitively, while the middle-aged group generated significantly greater absolute mechanical work and peak torque during the exercise protocol, it was the young group that demonstrated massively higher secondary CK and LDH efflux. The middle-aged group exhibited immediate sarcolemma fragility (elevated CK at 0 h) and structural resistance to FR-induced tissue softening. Despite distinct damage signatures, standardized FR effectively blunted secondary CK efflux, eradicated age-related disparities in LDH magnitude, and universally alleviated perceived soreness. Notably, objective mechanical restoration was not significantly correlated with subjective pain reduction. CONCLUSIONS:Biological aging and maximal eccentric exercise interacted to produce distinct damage signatures. Aging myofascial tissue appeared to provide a "mechanical shield" that protected against massive delayed-onset structural disruption despite sustaining greater absolute mechanical work, albeit exhibiting immediate membrane fragility and localized mechanical recalcitrance. Nevertheless, standardized FR serves as a potent physiological homogenizer and neuromodulator, effectively blunting secondary damage and alleviating soreness across demographics, independent of absolute mechanical tissue softening.
PURPOSE:Some data suggest that high-intensity interval exercise improves glycemic control more than continuous exercise. We aimed to identify the factor(s) that enhance insulin sensitivity during an oral glucose tolerance test (OGTT) after exercise. METHODS:Ten healthy, physically active individuals (including three females) completed three work-matched 50-minute exercise trials that differed in workload distribution. Using a randomized crossover design, participants completed: a) a moderate-intensity continuous exercise trial (MICE), b) a high-intensity interval exercise trial (HIIE), c) a high-intensity continuous exercise trial (HICE), and d) a no-exercise control trial (CONT). After exercise, insulin sensitivity (IS MATSUDA) was measured during the OGTT. Plasma glucose kinetics and oxidation rates were measured by infusion of isotopically labeled [U- 13C] glucose. Glycogen oxidation was calculated as the difference between total carbohydrate oxidation (assessed by indirect calorimetry) and plasma glucose oxidation. RESULTS:Total carbohydrate oxidation, plasma glucose oxidation, calculated glycogen oxidation, and plasma lactate accumulation during exercise were similar between HIIE and HICE, and both were higher than during MICE (p<0.05). Only HIIE decreased the postprandial insulin area under the curve, which increased IS MATSUDA index above CONT, MICE and HICE (15.5±4.3 vs.12.7±4.4; 12.5±6.1 and 11.8±6.0; p = 0.048, 0.030, 0.005, respectively). CONCLUSIONS:In summary, improvements in glycemic control following HIIE seem to be more related to its cyclic pattern than to glycogen use during the high-intensity segments. Our data suggest that exercise programs aimed at restoring glycemic control should emphasize workload cycling before engaging the high-intensity component.
BACKGROUND:Children with attention deficit hyperactivity disorder (ADHD) experience high rates of sleep problems and have an increased risk of executive dysfunctions and physical inactivity. Physical activity (PA) may be protective; however, few studies have objectively measured PA, sleep parameters and executive functions (EFs) in ADHD populations. This study aimed to assess PA and sleep using wearable motion sensors and to examine the relationships with EFs in children with ADHD. METHODS:The ActiGraph GT9X Link accelerometer was used to measure PA and sleep parameters in 282 children with ADHD (age range: 6-12 years; mean age = 8.59 ± 1.35 years; 78.4% boys) over seven consecutive days. Sleep status was assessed using the Pittsburgh Sleep Quality Index (PSQI), with scores ≥5 indicating poor sleep quality. Core EFs (i.e., inhibitory control, working memory, and cognitive flexibility) were assessed using Inquisit Lab™ 5. RESULTS:Within this large, well-characterized ADHD cohort, approximately 60% of children exhibited sleep problems. Compared with children with ADHD without sleep problems, those with sleep problems demonstrated longer actigraphy-derived sleep latency, poorer performance on cognitive flexibility tasks, spent less time per day in moderate-to-vigorous physical activity (MVPA), and were less likely to meet the World Health Organization-recommended 60 minutes of MVPA. Self-reported sleep quality, sleep efficiency, daytime dysfunction, and MVPA guideline attainment were significantly associated with EFs in children with ADHD. The relationships between daytime dysfunction and cognitive flexibility were moderated by MVPA guideline attainment. CONCLUSIONS:Daytime dysfunction predicts poorer cognitive flexibility only in children with ADHD who engage in low PA levels. Further investigation is warranted to determine whether adherence to MVPA guidelines can mitigate sleep problems and executive dysfunction.
