Medicine and Science in Sports and Exercise最新文献

Introduction: Individuals with anterior cruciate ligament reconstruction (ACLR) often walk with a less dynamic vertical ground reaction force (vGRF), exemplified by a reduced first peak vGRF and elevated midstance vGRF compared with uninjured controls. However, the mechanism by which altered limb loading affects actual tibial plateau contact forces during walking remains unclear.

Methods: Our purpose was to use musculoskeletal simulation to evaluate the effects of first peak vGRF biofeedback on bilateral tibiofemoral contact forces relevant to the development of post-traumatic osteoarthritis in 20 individuals with ACLR. We hypothesized that reduced first peak vGRF would produce less dynamic tibial plateau contact forces during walking in individuals with ACLR.

Results: As the pivotal outcome from this study, and in support of our hypothesis, we found that less dynamic vGRF profiles in individuals with ACLR-observations that have associated in prior studies with more cartilage breakdown serum biomarkers and reduced proteoglycan density-are accompanied by less dynamic tibiofemoral joint contact forces during walking.

Conclusion: We conclude that more sustained limb-level loading, a phenotype that associates with worse knee joint health outcomes after ACLR and was prescribed herein using biofeedback, alters the loading profile and magnitude of force applied to tibiofemoral cartilage.

Purpose: Developmental coordination disorder (DCD) is a common neurodevelopmental disorder characterized by motor impairments and subsequent physical activity (PA) deficits in middle childhood. It is not well understood when this gap in PA emerges. The purpose of the current study was to examine the longitudinal trajectories of device-assessed PA in a large cohort of children with and without DCD from ages 4 to 8 yr.

Methods: Children ( n = 535; age, 4-5 yr) completed four annual assessments as part of a prospective cohort study. Children were classified into three groups based on their average performance on the Movement Assessment Battery for Children-Second Edition: probable DCD <6th percentile ( n = 72), at risk for DCD between the 6th and 16th percentile ( n = 127), and typically developing >16th percentile ( n = 336). Moderate-to-vigorous PA (MVPA) and average PA volume (vector counts per minute) were assessed using ActiGraph accelerometers. A series of linear mixed-effects models were used to examine longitudinal PA trajectories between groups.

Results: Children in both the probable DCD and at-risk for DCD groups engaged in significantly less MVPA compared with the typically developing group, whereas the deficit in PA volume was only marginally evident in the probable DCD group. The rate of change did not differ by group, indicating that this deficit is relatively consistent across the early childhood period.

Conclusions: Young children with DCD are in an MVPA deficit that persists across early childhood. Early interventions targeting motor skills and PA may help to reduce this gap and promote positive trajectories of health among children with motor difficulties.

Purpose: This study compared the effects of four different resistance training (RT) programs that differed in the set configuration (cluster vs traditional) and the blood flow condition (free-flow [FF] vs blood flow restriction [BFR]) on strength, neuromuscular and hypertrophic adaptations.

Methods: Forty-two resistance-trained males were randomly assigned into four protocols that differed in the set configuration (TRA: without rest between repetitions versus CLU: 30 s rest every two repetitions) and in the blood flow condition (FF vs BFR [50% of arterial occlusion pressure]). Subjects followed an 8-week RT program, twice per week, with similar intensity (55%-65% 1RM), sets (3), repetitions per set (10-6), and resting time (2 min) in the full-squat (SQ) exercise. Before and after the RT program, they were evaluated for: 1) muscle size of the vastus lateralis ; 2) vertical jump; 3) maximal isometric contraction; 4) progressive loading test; and 5) fatigue test.

Results: BFR-TRA and FF-CLU induced greater increases in 1RM, and velocity against submaximal loads than FF-TRA and BFR-CLU (BFR-time and CLU-time interactions, P = 0.02). The TRA protocols showed greater increases in maximal isometric force than CLU (CLU-time interaction, P = 0.03). BFR did not enhance jump performance unlike the FF protocols ( P < 0.01). The TRA protocols induced greater hypertrophy in the distal region of the vastus lateralis than CLU protocols (CLU-time interaction, P = 0.04), with BFR-TRA producing the greatest gains in all vastus lateralis sections.

Conclusions: The different combinations of set configurations and blood flow conditions resulted in highly specific adaptations that illustrate the potential of adaptation for each protocol. The divergent underlying mechanisms of CLU and BFR methodologies may offset each other when combined.

Purpose: Cold limb immersion, a form of cryotherapy, can cause cardiovascular changes due to cold-pain induced autonomic reflexes. This cryotherapy treatment side effect has received less attention but could have direct implications for physical rehabilitation of individuals with cardiovascular comorbidities.

Methods: To test hypotheses related to the pressor effects of varied limb sites and surface areas of cryotherapy, two common lower limb injury sites (ankle and knee) were immersed into cold water (15 min, 1-3°C) and then referenced to a standard cold pressor test (CPT). Beat-by-beat arterial blood pressure (finger photoplethysmography), heart rate (ECG), systemic vascular conductance (SVC; Modelflow), and calf vascular conductance (VC) (venous occlusion plethysmography) were measured in 14 healthy participants.

Results: At 2 min, CPT increased mean arterial pressure (21 ± 4 mm Hg) more than either ankle or leg immersion (15 ± 4 and 15 ± 5 mm Hg, respectively; P = 0.015). Systemic vascular conductance and calf VC decreased but were not different across treatments ( P = 0.417 and P = 0.086). Mean arterial pressure and SVC were not different from 2 to 15 min of immersion ( P = 0.164 and P = 0.522), but calf VC decreased further by the end of immersion (3.1 ± 0.5 to 2.8 ± 0.4 and 2.7 ± 3 to 1.7 ± 0.2 units; P = 0.028). Mean arterial pressure increases with CPT were similar with solely CPT and when CPT followed ankle or leg immersion (27 ± 5 and 23 ± 4 mm Hg, respectively; P = 0.199).

Conclusions: These data indicate robust pressor responses without autonomic reflex habituation and that cryotherapy immersion location but not surface area appears to mediate cardiovascular responses. This cryotherapy side effect may be an important consideration for patients with cardiovascular-related comorbidities.

Introduction: A bout of vigorous endurance exercise transiently activates Toll-like receptor 4 (TLR4) and reduces TLR4 protein expressed on peripheral blood mononuclear cells (PBMCs). Endurance training, on the other hand, reduces TLR4-mediated signaling and minimizes the physiological stress imposed by exercise. Less is known about what occurs in skeletal muscle regarding TLR4 regulation and signaling. Therefore, this study aimed to investigate the regulation of TLR4 expressed in different tissue types (PBMCs and skeletal muscle samples) between endurance-trained and untrained men following vigorous endurance exercise and determine the effect of training status on cytokine responses associated with TLR4 activation.

Methods: Endurance-trained ( n = 7) and untrained ( n = 5) men cycled for 1 h at their respiratory compensation point, with blood and skeletal muscle samples collected pre- and 3 h post-exercise.

Results: In response to vigorous exercise, untrained men experienced a decrease in inhibitor of κBα (IκBα) protein (suggesting IκB degradation and the activation of TLR4-associated transcription factor NF-κB) and TLR4 protein levels, along with a simultaneous increase in TLR4 mRNA expression in both skeletal muscle and PBMCs. Moreover, this exercise session led to elevated levels of circulating interleukin-6, tumor necrosis factor-α, and interleukin-1β. Collectively, these results suggest a heightened TLR4-mediated signaling pathway in untrained men. However, no changes in these targets were observed in endurance-trained men, possibly indicating a potential mechanism by which regular endurance training blunts systemic inflammation.

Conclusions: These findings highlight the potential of endurance training to mitigate TLR4-mediated signaling, such as systemic inflammation, and shed light on the effects of exercise on TLR4 expression in PBMCs and skeletal muscle.

Purpose: The objective of this study is to examine sex-based differences in substrate oxidation, postprandial metabolism, and performance in response to 24-h manipulations in energy availability (EA), induced by manipulations to energy intake or exercise energy expenditure.

Methods: In a Latin Square design, 20 endurance athletes (10 females using monophasic oral contraceptives and 10 males) undertook five trials, each comprising three consecutive days. Day 1 was a standardized period of high EA; EA was then manipulated on day 2; postintervention testing occurred on day 3. Day 2 EA was low/high/higher EA (LEA/HEA/GEA) at 15/45/75 kcal·kg -1 FFM·d -1 , with conditions of LEA and HEA separately achieved by manipulations of either energy intake or exercise energy expenditure (LEA REST/EX vs HEA REST/EX ). On day 3, fasted peak fat oxidation during cycling and 2-h postprandial (high carbohydrate and energy meal) metabolism were assessed, alongside several performance tests: Wingate, countermovement jump, squat jump, isometric mid-thigh pull, and the Stroop color and word test.

Results: Highest peak fat oxidation occurred under LEA induced by exercise ( P < 0.01), with no difference between sexes. Postprandial glucose ( P < 0.01) and insulin ( P < 0.05) responses were highest across both sexes when LEA was induced by diet. Relative peak and mean power throughout the Wingate, alongside countermovement jump height did not differ between EA conditions ( P > 0.05), whereas squat jump height was lower during GEA than both LEA REST ( P = 0.045) and HEA EX ( P = 0.016). Isometric mid-thigh pull peak force and the Stroop effect did not change with altered EA ( P > 0.05).

Conclusions: Acute (24-h) exercise-induced LEA influenced fasted substrate oxidation more than diet-induced LEA, whereas 24 h of LEA did not impair strength/power, sprint capacity, or cognitive performance. Finally, the responses to EA manipulations did not differ between sexes.

Purpose: Findings from previous Mendelian randomization (MR) studies disagreed with the current scientific consensus regarding the role of physical activity (PA) and sedentary behavior in ischemic stroke (IS). We reassessed these associations with a focus on etiological subtypes of IS and the potential mediating roles of cardiometabolic traits and brain imaging-derived phenotypes (IDPs).

Methods: We performed MR analyses using summary statistics from genome-wide association studies of sedentary behavior and PA ( n = 88,411 ~ 608,595), cardiometabolic traits ( n = 393,193 ~ 694,649), brain IDPs ( n = 33,224), and the latest IS data (62,100 cases and 1,234,808 controls). Inverse-variance weighted regression was used as the primary method, complemented by several sensitivity analyses. A two-step MR approach was employed to assess the mediating effects of cardiometabolic traits and brain IDPs.

Results: Genetic liability to leisure-time moderate-to-vigorous PA (MVPA) and higher overall PA (OPA) were associated with reduced risks of IS and small vessel stroke (Benjamini-Hochberg adjusted P < 0.05). Suggestive associations were observed between longer leisure-screen time and higher IS risk and between higher OPA and lower cardioembolic stroke risk ( P < 0.05). The isotropic volume fraction in the anterior limb of the left internal capsule, as well as some cardiometabolic metrics, partially mediated these associations. There was no evidence for causal effects of overall MVPA, overall light-intensity PA, or overall sedentary duration on IS.

Conclusions: Longer leisure screen time, less OPA, and not engaging in MVPA during leisure time were associated with higher risk of IS. The associations between PA and IS depended on different subtypes and were mediated by changes in anterior limb of the left internal capsule and cardiometabolic biomarkers.

Introduction: Individuals with Down syndrome (DS) exhibit autonomic dysfunction, which contributes to reduced work capacity. The metaboreflex produces exercise-induced sympathoexcitation and can be assessed via post-exercise muscle ischemia (PEMI). Blunted sympathoexcitation is common in individuals with DS and contributes to the physiological basis for reduced work capacity observed this population, but the influence of the metaboreflex is unknown. Using unilateral isometric knee extension exercise with PEMI, we hypothesized that individuals with DS would demonstrate a reduced metaboreflex compared with individuals without DS.

Methods: Twenty-four individuals with DS (M/F: 13/11; 24 ± 5 yr; 30.3 ± 6.2 kg·m -2 ) and without DS (M/F: 13/11; 25 ± 4 yr; 26.5 ± 4.5 kg·m -2 ) performed a unilateral isometric knee extension at 30% of their maximal voluntary contraction on a leg dynamometer. Following 2 min of contraction, a thigh cuff was rapidly inflated to 220 mm Hg on the exercised leg for 3 min to isolate the activation of the muscle metaboreflex via PEMI. Beat-to-beat mean arterial pressure (MAP) and systolic blood pressure (SBP) were assessed using finger photoplethysmography. Heart rate (HR) was collected via three-lead electrocardiogram.

Results: Despite similar baseline values of all variables in both groups, individuals with DS demonstrated a blunted pressor response to unilateral isometric knee extension compared with individuals without DS (MAP; DS: 103 ± 14 vs non-DS: 125 ± 19 mm Hg), and the blunted MAP response was maintained with PEMI (MAP; DS: 95 ± 13 vs non-DS: 106 ± 18 mm Hg; group-time interaction, P < 0.001). Individuals with DS also exhibited reduced HR 2 min into contraction compared with individuals without DS (HR; DS: 90 ± 16 vs non-DS: 114 ± 22 bpm; group-time interaction, P < 0.001).

Conclusions: Individuals with DS demonstrated a diminished metaboreflex response compared with their peers without DS, during a task known to induce sympathoexcitation. Our findings suggest that reduced influence of the metaboreflex contributes to the reduced exercise pressor response in individuals with DS. Such exercise-specific peripheral autonomic alterations extend beyond our previous cardiac autonomic findings demonstrating blunted sympathoexcitatory perturbations in individuals with DS, which may contribute to reduced work capacity observed in this population.

Introduction: Perceived groove, a complex and integrated musical characteristic, is considered a core factor in inducing synchronization between movement and music. This study aimed to use functional near-infrared spectroscopy to explore the effective connectivity (EC) changes among brain regions during cycling activities under different perceived groove conditions.

Methods: In a randomized crossover design, 18 university students performed 3-min cycling tasks under high (HG) and low (LG) perceived groove music conditions. Revolutions per minute, coefficient of variation of pedaling cadence, and sensorimotor coupling index were measured. Granger causality analyses were performed on the functional near-infrared spectroscopy data from the cycling task to obtain EC matrices at the brain region and channel (Ch) levels.

Results: The revolution per minute was significantly higher, and coefficient of variation of pedaling cadence and sensorimotor coupling index were significantly lower in HG than in LG. The EC values of the Brodmann area (BA) 8→the left prefrontal cortex (lPFC), the superior portion of BA 6 (BA 6_Sup)→lPFC, and BA 1-3→lPFC were significantly higher in HG than in LG. Channel analyses indicated that the EC values of Ch 14→Ch 9, Ch 41→Ch 9, Ch 14→Ch 10, Ch 41→Ch 10, Ch 31→Ch 10, and Ch 35→Ch 23 were significantly higher in HG than in LG. Correlation analysis revealed that the EC values of the channels included in BA 6_Sup→lPFC were significantly correlated with cycling performance metrics.

Conclusions: The EC changes from BA 6_Sup to lPFC may play a critical role in the process through which perceived groove affects the synchronization of cycling to music.

Introduction: Plantar fasciitis (PF) is one of the most common running-related injuries.

Purpose: The aim of this prospective study was to determine the incidence of PF and identify potential risk or protective factors for PF in runners and non-runners.

Methods: Data from 1206 participants from the 4HAIE cohort study (563 females/643 males; 715 runners/491 non-runners; 18-65 yr of age) were included in the analysis. We collected biomechanical data during overground running using a three-dimensional motion capture system at the baseline and running distance data via retrospective questionnaires and followed the participants for 12 months following the baseline data collection. Participants were asked weekly about any sports-related injury (including PF). A binary logistic regression was performed to reveal potential associations between running distance and biomechanical risk factors and PF while controlling for running distance, sex, and age.

Results: The total incidence of PF was 2.3% (28 PF from 1206 participants), 2.5% in runners and 2.0% in non-runners ( P = 0.248). Runners who ran more than 40 km·wk -1 had six times higher odds of suffering PF than individuals who ran 6-20 km·wk -1 ( P = 0.009). There was a significant association between maximal ankle adduction and PF; that is, runners with a lower abduction angle during the stance period had higher risk of PF ( P = 0.024). No other biomechanical variables indicated significant associations with PF.

Conclusions: Regular running with a moderate weekly volume and more toeing out of the foot relative to the shank may reduce the risk against PF in runners, which may be useful for researchers, runners, coaches, and health professionals to minimize PF injury risk.