Medicine and Science in Sports and Exercise最新文献

Purpose: This study evaluated whether recombinant human erythropoietin (rhEpo) treatment combined with hypoxia provided an additive effect on hemoglobin mass (Hbmass) and V̇O2peak compared to altitude or rhEpo alone.

Methods: 39 participants underwent two interventions, each containing 4 weeks baseline (PRE 1-4), 4 weeks exposure at sea level or 2,320 m of altitude (INT 1-4), and 4 weeks follow-up (POST 1-4). Participants were randomly assigned to 20 IU·kg-1 rhEpo or placebo injections every second day for 3 weeks during the exposure period at sea level (SL-EPO n = 25, SL-PLA n = 9) or at altitude (ALT-EPO n = 12, ALT-PLA n = 27).

Results: Hbmass displayed a significant time×treatment effect (P < 0.001) when comparing ALT-EPO and ALT-PLA. Specifically, the increase in Hbmass was higher (P < 0.05 to P < 0.001) for ALT-EPO from INT 2 to POST 3 except for POST 2. Similarly, a significant time×treatment effect (P < 0.001) existed for changes in Hbmass when comparing ALT-EPO with SL-EPO, with the increase in Hbmass being higher (P < 0.01 to P < 0.001) for ALT-EPO from INT 2 to POST 4. A significant time×treatment effect was present when SL-PLA was compared with ALT-PLA (P < 0.05) and SL-EPO (P < 0.05). For V̇O2peak the time×treatment interaction was not significant when comparing ALT-EPO to ALT-PLA. However, when ALT-EPO was compared with SL-EPO, a significant time×treatment interaction existed (P < 0.001) due to a decrease in V̇O2peak during altitude.

Conclusions: The combined treatment of micro-doses of rhEpo and altitude exposure results in an additive increase in Hbmass but does not significantly enhance V̇O2peak compared to each treatment alone.

Purpose: Substrate metabolism during exercise may vary across the menstrual cycle (MC) phases, likely due to estradiol (E2) and progesterone (P4). This study examined substrate metabolism during exercise in naturally menstruating (NoOC, n = 34) and women using combined oral contraceptives (COC, n = 19).

Methods: Participants were measured in a fasted state in the follicular (FOL) and luteal (LUT) phases, or the inactive (INACT) and active (ACT) phases of COC use. Serum E2 and P4 were assessed using immunoassays and body composition via bioimpedance. Peak fat oxidation (PFO) and FATMAX, the intensity eliciting PFO, were evaluated using indirect calorimetry. FATMAX was calculated using peak oxygen uptake (V̇O2PEAK), measured on the following day.

Results: PFO did not differ between FOL and LUT (0.40 ± 0.09 g·min-1 vs. 0.41 ± 0.10 g·min-1, p = 0.482) or INACT and ACT (0.48 ± 0.12 g·min-1 vs. 0.44 ± 0.11 g·min-1, p = 0.099). FATMAX showed no phase-related variation (NoOC: FOL 47.3 ± 15.7 % vs. LUT 47.7 ± 13.6 %, p = 0.727; COC: INACT 57.1 ± 12.3 % vs. ACT 52.5 ± 12.2 % p = 0.172). PFO was 0.08 g·min-1 (95 % confidence interval: 0.02 g·min-1-0.14 g·min-1, p = 0.010) and FATMAX 9.8 % (95 % CI: 1.0-8.7 %, p = 0.031) higher in the INACT vs. FOL. The difference in PFO persisted after adjusting for fat-free mass and V̇O2PEAK (p = 0.033) but was not significant after excluding an outlier from the COC group (p = 0.108).

Conclusions: PFO and FATMAX remained stable between MC and COC phases, suggesting no need to standardize measurements by cycle phase. However, higher PFO and FATMAX in the COC group during INACT compared to FOL suggests distinct effects of exogenous hormones on metabolism compared to endogenous hormones. Practitioners should consider these differences when assessing factors influencing substrate metabolism.

Purpose: Exercise is widely recognized for providing numerous benefits to prostate cancer (PCa) survivors. Numerous preclinical studies have investigated the role of exercise on tumor progression, but results are often controversial, largely due to variations in experimental protocols.

Methods: In this study, the comprehensive effects of exercise on PCa were evaluated with two different aerobic exercises, forced and structured Exercise Training on treadmill (ET), and Voluntary Wheel Running (VWR). Human PCa PPC-1 cells or PBS were injected into athymic nude mice, randomized into four groups: healthy, cancer control (CaCTL), cancer with exercise training (CaET), and cancer with voluntary wheel running (CaVWR).

Results: ET significantly reduced tumor growth (290.38 ± 75.43 mm3) compared to CaCTL mice (374.84 ± 86.15 mm3, p = 0.0227). ET also regulated plasma IL-6 concentration, protected against cancer-induced adipose tissue loss (CaCTL = 171.21 ± 86.73 mg; Ca ET = 341.71 ± 137.24 mg, p = 0.0295) and preserved strength (CaCTL = 126.53 ± 6.68 g; CaET = 137.32 ± 6.39 g, p = 0.0018). However, ET did not protect against cancer-induced muscle mass loss (CaCTL = 175.06 ± 18.07 mg; CaET = 181.41 ± 14.59 mg). In contrast, VWR did not provide similar benefits on the assessed cancer-related outcomes, aside from preserving muscle strength (CaCTL = 126.53 ± 6.68 g; CaVWR = 134.59 ± 7.01 g, p = 0.0204).

Conclusions: ET represented an effective strategy against PCa by limiting tumor growth, but also by mitigating inflammation and adipose tissue loss and preserving muscle strength, whereas VWR only provided limited benefits. The exercise parameters are emerging as a critical factor in combating PCa, warranting further investigation.

Background: Both insufficient physical activity (PA) and excess body weight are important risk factors for cardiovascular disease (CVD), and PA is closely related to body weight. However, it remains unclear whether PA modifies or mediates the association of body mass index (BMI) with CVD.

Methods: We conducted a cross-sectional study of 35,406 adults participating in the National Health and Nutrition Examination Survey (NHANES). The mediation and interaction effects of PA were assessed using a four-way decomposition approach. An additional two-step Mendelian randomization (MR) analysis was performed to verify the potential causal mediation effect.

Results: A strong association was observed between PA and lower odds of CVD after adjusting for all confounders [Odds Ratio (OR): 0.84; 95% Confidence Interval (CI): 0.74-0.95]. Increased BMI was associated with higher odds of CVD (OR: 1.04; 95% CI: 1.03-1.04). PA showed interaction and mediation effects on the association of BMI with CVD. The overall proportion attributable to interaction was -37.5%, while the overall proportion attributable to mediation was 22.2%. MR analysis further confirmed that PA causally mediated the pathway from BMI to CVD.

Conclusions: PA modified the association of BMI with CVD, suggesting that sufficient PA is needed to lower the impact of high BMI on CVD risk. Moreover, we found that PA served as a causal influence on the association of BMI with CVD, indicating that higher BMI led to a lower level of PA, which in turn increased the risk of CVD.

Purpose: Stress is a risk factor for psychiatric illnesses. However, not all individuals exposed to stress will develop affective disorders. We examined whether pretreatment with stress-free voluntary wheel running (VWR) exercise prophylactically enhances stress resilience in rodents and how it can effectively prevent the development of depressive- and anxiety-like behaviors.

Methods: Eight-week-old C57BL6/J mice were housed in cages with VWR and subjected to chronic restraint stress (CRST) for 2 h daily for 14 days. The mice were assessed for depressive- and anxiety-like behaviors, and a behavioral matrix (k-means clustering) was introduced to segregate the mice into susceptible and resilient subpopulations. Chemogenetic inhibition and retrograde tracing were used to map the neural circuits involved in VWR's resilience-enhancing properties.

Results: After CRST exposure, 71.50% of CRST mice with VWR were stress resilient, with less stress-induced prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis and corticosterone (CORT) response, representing a 57.20% increase compared with CRST-only mice. Staining for c-Fos showed that VWR activated predominantly hippocampal GABAergic neurons and suppressed the activity in the medial prefrontal cortex (mPFC). Chemogenetic inhibition of the ventral hippocampus (vHPC) dissipated the antidepressant and anxiolytic effects of VWR pretreatment. In addition, the nucleus reuniens (NR) was implicated in VWR's resilience-enhancing properties, relaying reciprocal interactions of the mPFC-vHPC pathway.

Conclusions: These findings suggest that stress-free voluntary exercise may be an effective modality for stress management and warrant further investigation into its resilience-enhancing mechanisms.

Purpose: The aim of the present study was to compare performance and physiological effects, and inter-individual response variation in performance and its physiological determinants between heart rate-based (HR), race pace-based (RP) and heart rate variability-based (HRV) training prescription approaches in recreational distance runners.

Methods: Twenty-eight participants completed a 6-week endurance training intervention after being randomly assigned to three groups: HR (n = 9), RP (n = 9), and HRV (n = 10) training prescription approaches.

Results: No interaction effects between groups were observed. Main time effects were found for absolute and relative V̇O2max, running economy (RE), speeds associated to the first (sVT1) and second ventilatory thresholds (sVT2) and 7 km time trial performance (TT) (p < 0.001, 0.88 ≤ d ≤ 2.67). The RP group improved TT (p < 0.05, ES = 1.07), showing greater effectiveness in enhancing maximal aerobic speed and fat mass reduction, but did not consistently improve physiological parameters like sVT2 or RE. The HRV method increased sVT2 (p < 0.01, ES = 1.34) and was more successful in boosting sVT1 and V̇O2max, although it resulted in an increase in fat mass. Training load was similar between groups (p > 0.05), and a pyramidal training intensity distribution model was found in all groups. The lowest inter-individual response variation in TT was found in the RP group (coefficient of variation [CV] = 0.82), whereas the HRV group demonstrated a lower variation in relative V̇O2max (CV = 0.75) and sVT2 (CV = 0.79).

Conclusions: The RP approach is an effective and useful training prescription method for optimising performance in recreational runners, while the HRV method proves valuable for enhancing key physiological markers.

Purpose: Occupational heat strain can impair construction workers' motor and cognitive functions, potentially leading to accidents, injuries and lowered productivity. We examined the effects of physical work under various warm and humid tropical conditions on performance in virtual reality (VR)-based construction tasks.

Methods: Eighteen healthy men (age: 29 ± 5 years) completed three randomised, counterbalanced experimental trials comprising ~2.5 h of exposure to wet-bulb globe temperatures of 24.6 ± 0.2 °C (COOL), 28.1 ± 0.3 °C (WARM) and 32.4 ± 0.3 °C (HOT), representing Singapore's current (COOL and WARM) and projected (HOT) conditions. Participants performed three 30-min bouts of treadmill walking at fixed metabolic heat productions representing light (EX1: 250 W), moderate (EX2: 350 W) and heavy (EX3: 450 W) workloads, each separated by completion of a battery of VR-based construction tasks (welding and plank-walking at height). Task speed and accuracy, postural sway and gait were recorded during the VR tasks, while body core (Tc) and mean skin temperatures (Tsk), and heart rate (HR) were recorded continuously.

Results: Post-trial Tc was higher in HOT (38.6 ± 0.4 °C) compared with WARM (38.1 ± 0.3 °C; P < 0.001) and COOL (37.9 ± 0.3 °C; P < 0.001), while mean Tsk (P < 0.001) and HR (P < 0.001) differed between all conditions (HOT>WARM>COOL). Task speed and accuracy during welding and plank-walking were similar between conditions (all P > 0.05). However, postural sway velocity during welding increased (by 2.08 ± 2.5 mm.s-1; P < 0.05) from baseline to post-trial in HOT but not in WARM or COOL (both P > 0.05).

Conclusions: Although task performance was maintained across environments, postural balance during an attention-demanding task (welding) was impaired following physical work in Singapore's projected environmental conditions, which could increase the risk of potentially fatal accidents and injuries (e.g., falling from height). Effective workplace interventions are needed to protect workers' health, safety and productivity against future warming.

Purpose: Determine the associations of body mass index (BMI) and body composition (lean and fat mass) with i) patient-reported outcomes, ii) quadriceps strength, and iii) physical performance in anterior cruciate ligament reconstruction (ACLR) patients.

Methods: Thirty-four individuals participated (56% female; 22 ± 4 years; % body fat: 22.9 ± 6.7%). Dual energy x-ray absorptiometry was used to measure percent lean (%LM) and fat (%FM) mass for the whole-body, and the whole-limb and thigh region of the ACLR limb. Knee Injury and Osteoarthritis Outcomes Score (KOOS) subscales were used to evaluate patient-reported outcomes. Isometric quadriceps strength (MVIC) was measured using an isokinetic dynamometer with the knee flexed at 90 degrees. Single-leg hop (SLH) distance was used to evaluate physical performance. Spearman rank correlations were used to separately evaluate the associations between BMI and body composition with KOOS, MVIC, and SLH.

Results: BMI was not significantly associated with KOOS, MVIC, or SLH (p > 0.05). Greater whole-body %LM associated with greater MVIC and SLH, while greater whole-body %FM associated with worse KOOS ADL, MVIC, and SLH (p < 0.05). Greater whole-limb %LM associated with greater MVIC, while greater whole-limb %FM associated with worse KOOS Symptoms, Pain, QoL, and MVIC (p < 0.05). Greater thigh %LM associated with better KOOS Symptoms and MVIC, and greater thigh %FM associated with worse KOOS Symptoms, Pain, QoL, and MVIC (p < 0.05).

Conclusions: Body composition characteristics of higher %LM and lower %FM associated with better clinical outcomes in ACLR patients of normal BMI status, thereby elucidating a potential modifiable target to mitigate poor ACLR-related outcomes. Future research should further evaluate mechanistic links between body composition and ACLR-related outcomes to inform clinical practice and rehabilitation frameworks.

Purpose: The purpose of this study was to investigate the effects of heating on Achilles tendon mechanical properties (elongation, elastic energy, and hysteresis) and performance during stretch-shortening cycle exercise (pre-stretch augmentation and efficiency).

Methods: Fifteen males participated in this study. Before and after heating (30 min) and non-heating (control) conditions, the mechanical properties of the Achilles tendon during ramp and ballistic contractions and two kinds of jumps (no-countermovement and countermovement jumps) were measured. In addition, electromyographic activities of the plantar flexor muscles (medial gastrocnemius, lateral gastrocnemius, and soleus muscles) and oxygen consumption were measured during 5 min of submaximal repetitive jumps after both interventions (heating and control).

Results: Although no changes in tendon elongation at all force levels and elastic energy during ramp and ballistic contractions were observed, tendon hysteresis decreased by 14.2% during ramp contraction (p = 0.015 according to the paired t-test) and 8.0% during ballistic contraction (p = 0.006 according to the paired t-test) after heating. No changes in no-countermovement and countermovement jump heights were found after both interventions. The electromyographic activities of gastrocnemius muscles at the first half and soleus muscle at all time points were significantly lower for heating than for control conditions. No difference in oxygen consumption was found between heating and control conditions.

Conclusions: These results suggest that heating reduces tendon hysteresis and enhances efficiency (assessed by electromyographic activity) during repetitive submaximal jumps.

Introduction: Females are prone to knee ligament injuries compared to males. Moment arms describe the mechanical advantage of ligaments to stabilise the knee from injurious moments. Compared to males of the same stature, females have a smaller femoral epicondylar width, which we hypothesised would reduce their knee joint ligament moment arms in the frontal plane.

Methods: To calculate varus-valgus ligament moment arms, we created 26 patient-specific finite element models (17F; 9 M) and simulated an axial load of half body weight. Tibial cartilage contact pressures were obtained and used to define the medial and lateral peak contact pressure, which were assumed to be the point of rotation in the frontal plane. The varus and valgus moment arms of the anterior cruciate (ACL) and the medial (MCL) and lateral collateral ligaments (LCL) were calculated as the perpendicular distance between the point of peak contact pressure and the centroid of each ligament. Multiple linear regression models with sex, height, and epicondylar width as independent variables were produced.

Results: Females had smaller varus-valgus ligament moment arms compared to males, with a mean difference of 7 to 9 mm observed by the MCL and LCL about the lateral and medial contact points, respectively (~12% smaller, p < 0.001). The female cohort exhibited ACL moment arms about the medial and lateral contact points that were ~ 4 mm less than the male cohort (p < 0.05). Correlations between varus-valgus ligament moment arm and epicondylar width were found for all three ligaments using either the medial or lateral points of peak contact pressure.

Conclusions: These findings support our hypothesis that females have smaller varus-valgus ligament moment arms compared to males, which could contribute to the higher rate of female ligament injuries compared to males.