Medicine and Science in Sports and Exercise最新文献

Purpose: Load carriage and tactical mobility are military tasks that pose significant risks for musculoskeletal injuries (MSKI) in military personnel. This investigation compared biomechanical and physiological demands of a load carriage and tactical mobility task and examined their differences between sexes using reliable and validated wearables among United States Marine officer candidates.

Methods: Forty-one candidates (16 women) performed a 15.8-km loaded ruck march and a 4.0-km endurance course that assessed load carriage and tactical mobility performance, respectively. Inertial measurement units on the distal tibia and wrist-worn watches collected biomechanical (total step count, impact load, bone stimulus, average intensity, low-/medium-/high-g step count) and physiological (heart rate (HR mean , HR min , HR max ), physical activity energy expenditure (PAEE), and metabolic equivalent (MET mean )) data. Paired sample t -tests compared metrics between events. Principal component (PC) analyses interpreted event demands. Independent samples t -tests analyzed sex differences between PCs ( α = 0.05).

Results: Impact load (+1259.70 g ·min -1 , P < 0.001), average intensity (+7.20 g , P < 0.001), bone stimulus (+126.73 AU, P < 0.001), high- g steps (+559.34 g , P < 0.001), HR min (+13.15 bpm, P < 0.001), HR mean (+28.79 bpm, P < 0.001), HR max (+16.95 bpm, P < 0.001), and MET mean (-1.93 kcal·kg -1 ·h -1 , P < 0.001) were higher during the endurance course than the ruck; step count (-14,934, P < 0.001) and PAEE (-713 kcal, P < 0.001) were lower. Three PCs explained 84.3% and 81.5% of variance for the ruck and endurance course. PC1 represented biomechanical variables, PC2 physiological variables, and PC3 g step count. Sex differences were found in PC2 ( P = 0.039) and PC3 ( P = 0.002) for the ruck, and PC3 ( P < 0.01) for the endurance course revealing greater demands on women.

Conclusions: Tactical mobility requires greater biomechanical and physiological demands than load carriage and places greater demands on women. Task and sex-specific training strategies may improve performance and mitigate MSKI risk.

Purpose: This secondary analysis of a randomized controlled trial (RCT) of resistance exercise training (RET) compared with a waitlist quantified the acute effects of a single resistance exercise session on depressed mood state.

Methods: Sixty-two young adults (26.6 ± 5.6 yr; 39 female) were randomized to 8 wk of World Health Organization and American College of Sports Medicine guidelines-based RET or a waitlist, with an acute RCT nested in at week 1. In the first session, RET participants completed moderate-intensity resistance exercise, comprising two sets of 8-12 repetitions of eight exercises targeting the major muscle groups. Waitlist participants completed 30 min of quiet rest. The Depression subscale of the Profile of Mood States Brief Form (POMS-B) measured depressed mood state pre- and 10 min post-session. Two group × two time (pre/post) RMANOVAs examined differences between resistance exercise and quiet rest. Subanalyses were conducted among young adults with analogue generalized anxiety disorder (AGAD), major depressive disorder (AMDD), comorbid AGAD and AMDD, and pre-exercise POMS-B ≥1 and ≥4.

Results: No significant group-time interaction ( F(1,59) = 1.70, P = 0.198) was found for depressed mood state. Significant main effects for time were found among the total ( F(1,59) = 14.74, P < 0.001), AGAD ( F(1,28) = 13.22, P ≤ 0.001), AMDD ( F(1,12) = 5.12, P ≤ 0.043), POMS-B ≥1 ( F(1,31) = 30.29, P < 0.001) and ≥4 ( F(1,11) = 10.71, P = 0.007) samples, such that depressed mood state reduced following a single bout of resistance exercise ( d = 0.29 to 1.26) and quiet rest ( d = 0.27 to 0.39).

Conclusions: Resistance exercise and quiet rest elicited significant small-to-large and small-to-moderate magnitude reductions in depressed mood state, respectively, that were not significantly different from each other.

Background/purpose: Current knowledge of the association between body composition and health outcomes is based on traditional regression techniques, where the components of body composition are treated as noncompositional independent variables. Mounting evidence suggests that body tissues are biologically co-dependent and therefore, require a statistical technique that considers this. This study used a compositional data analysis framework to explore the longitudinal association between body composition and a continuous metabolic syndrome score.

Methods: Participants included 288 physically inactive adults (age: 56 ± 12 yr [mean ± SD]; 56% female) with overweight or obesity (body mass index: 31.3 ± 3.5 kg·m 2 ) who participated in randomized controlled trials that determined the effects of exercise on adipose tissue (visceral, abdominal subcutaneous, peripheral subcutaneous, other adipose tissues) and lean tissues (skeletal muscle, other lean tissues) assessed by whole-body magnetic resonance imaging.

Results: Visceral adipose tissue, relative to the mass of the remaining tissues, was significantly associated with the metabolic syndrome score preintervention and postintervention ( P < 0.05). The slopes and intercepts of the preintervention and postintervention regression lines between relative visceral adipose tissue mass and metabolic syndrome did not differ ( P > 0.2). For a given weight loss, the greater the relative reduction in visceral adipose tissue, the larger the decrease in the predicted metabolic syndrome score.

Conclusions: This novel compositional data analysis reinforces that visceral adipose tissue is an important marker of cardiometabolic risk and should be a primary target for therapeutic strategies in individuals with overweight or obesity.

Purpose: Military training includes multiple stressors that together may increase risk for illness by degrading immune function and altering gut microbiota. However, whether sex differences exist in those responses is undetermined. This study aimed to determine immune and gut microbiota responses during military training and identify sex differences in those responses.

Methods: Seventy-two military cadets (33% female) participated in an arduous 17-d training event. Blood, saliva, and stool were collected upon beginning (PRE) and completing (POST) training. Immune function was assessed by salivary secretory IgA (SIgA), latent virus reactivation, peripheral leukocyte distribution, circulating cytokines, and mitogen-stimulated cytokine profiles. Gut microbiota composition was assessed by 16S rRNA amplicon sequencing.

Results: Participants experienced a ~4% body weight loss and sex-independent increases in concentrations of cortisol, myoglobin, catecholamines, and multiple cytokines. The granulocyte-to-lymphocyte ratio increased and SIgA decreased PRE to POST in males but not females ( Pinteraction ≤ 0.02). Mitogen-stimulated cytokine profiles were generally reduced at POST versus PRE independent of sex. No differences in virus reactivation were observed. Sex differences in gut microbiota responses were limited to Bifidobacterium and Ruminococcus , which increased in males relative to females (log 2 fold change (FC) = 2.0-2.4; qinteraction = 0.19). Independent of sex, 24 genera differed at POST versus PRE with Lactobacillus demonstrating the largest decrease (log 2 FC = -0.90; qtime = 0.02) and Veillonella the largest increase (log 2 FC = 1.09; qtime = 0.03). Multiple correlations between markers of stress, immune function, and gut microbiota composition were observed ( q ≤ 0.15).

Conclusions: Immune redistribution, leukocyte compromise, and interrelated changes in gut microbiota composition were evident within this training environment. Those responses demonstrated associations with markers of stress severity but also sex differences, suggesting a more pronounced depression of immune function in males.

Background: Prior high-intensity exercise (priming) has been shown to accelerate the oxygen uptake (V̇O 2 ) kinetics, as well as improve exercise tolerance during subsequent high-intensity exercise, yet the mechanisms underpinning the performance changes are unclear. In theory, a reduced reliance on non-oxidative energy input afforded by the faster V̇O 2 response may improve subsequent performance by delaying muscle fatigue; however, this effect has yet to be conclusively shown.

Purpose: Our purpose was to explore the impact of priming exercise on the energetic response, exercise tolerance, and the kinetics of muscle fatigue during severe-intensity cycling exercise.

Methods: Fourteen participants completed constant power cycling trials in the severe domain, preceded by either a bout of heavy intensity or an equivalent duration cycling at 20 W. Muscle fatigue was assessed in real time via femoral nerve stimulation while pedaling, and energetic contributions were assessed via V̇O 2 and changes in blood lactate concentration. Quadriceps oxygenation and surface electromyography (EMG) were also measured.

Results: Priming improved time-to-task failure (450 ± 74 s) compared with control (391 ± 92 s) ( P = 0.008). Relative oxidative contributions increased following priming ( P = 0.001), whereas the non-oxidative glycolytic contribution was reduced ( P < 0.0001), and this was accompanied by a reduction in the rate of quadriceps twitch force decline ( P = 0.041). Vastus lateralis EMG root mean square amplitude and M-wave amplitude increased across the trial similarly in both conditions, but priming resulted in a relative "downshift" in both measures ( P ≤ 0.027).

Conclusions: Priming exercise resulted in an improvement in exercise tolerance, attenuation in muscle fatigue, and reduction in EMG and M-wave amplitude. We speculate that these effects may arise in part from the interaction between a reduction in metabolite accumulation and altered sarcolemmal excitability.

Purpose: A common side effect of cancer and anticancer treatment is cancer-associated cachexia (CAC), a multifactorial syndrome characterized by the loss of bodyweight, skeletal muscle, and adipose tissue. Recommended therapeutic options are multidimensional, including nutritional, pharmacological, and exercise interventions. A novel therapeutic approach is the use of low-load resistance training combined with blood flow restriction to the trained limbs (LL-BFR). It has been shown to induce adaptations in muscle mass and strength despite a low training load in various clinical populations and might be a suitable training modality for cancer patients suffering from CAC.

Methods: A 56-year-old female patient diagnosed with stage IV gallbladder cancer, suffering from CAC, performed LL-BFR training twice weekly for 12 wk and received a guideline-based nutritional intervention. All outcome measures (maximal strength (8RM), handgrip strength, body mass, lean body mass, body cell mass, quality of life (QoL), and symptom burden) were evaluated before and directly after the training period.

Results: Adherence was moderate (67% of all training sessions completed), and no adverse events were noted. All measures of physical capacity and body composition improved between 19% to 55% and 9% to 11%, respectively. QoL decreased in 5/6 subscales, while symptom burden increased in 2/4 subscales.

Conclusions: Treatment of CAC requires a multitargeted and interdisciplinary approach. This is the first case study using LL-BFR training in an oncological patient during active therapy. Our results show that LL-BFR was feasible and, despite no positive effect on QoL and symptom burden, could induce relevant changes of muscle strength and muscle mass in a relatively short training period. Further research is necessary to confirm the results of this case study in randomized controlled trials.

Purpose: Existing literature indicates that physical fitness affects endogenous pain modulation capacity, potentially impacting populations with impaired pain modulation ability. However, current evidence remains inconsistent, and there is a lack of studies employing objective measures to examine this relationship. The objective of this study was to assess whether individual physical performance levels can predict endogenous pain modulation variables in the electroencephalogram (EEG).

Methods: The EEG-based somatosensory response following noxious mechanical stimulation was recorded as pinprick-evoked potentials during conditioned pain modulation (CPM) in 32 healthy adults. To analyze physical fitness, cardiorespiratory fitness (CRF) was measured by using spiroergometric analysis, and strength was tested using isokinetic strength testing. Bivariate linear regressions were calculated to analyze a potential relationship between physical performance parameters and CPM variables.

Results: Subjects with higher CRF exhibited a greater decrease in the event-related spectral perturbations in the CPM paradigm in the EEG and a correspondingly lower activation during a conditioning stimulus. The CRF predicted 14.0% of the variance in the activation during the conditioning stimulus (large effect) and 10.2% of the decrease in the event-related spectral perturbations in the CPM paradigm (moderate effect). No such relationship was observed between strength and EEG-based variables. When the groups were separated according to their physical fitness levels, no differences were observed between the groups during isolated mechanical stimulation.

Conclusions: The results indicate that CRF is associated with altered somatosensory responses during the CPM paradigm in our EEG-based pattern. Higher CRF appears to facilitate pain modulation processes without affecting central sensitivity to noxious mechanical stimulation, highlighting the potential benefits of higher levels of endurance exercise, but not strength levels.

Introduction/purpose: This study investigated the effect of breast size on running economy, breast displacement, total body center of mass excursion, trunk angular velocity, and exercise-induced breast pain at different running velocities.

Methods: Fifteen female recreational runners with a small breast size (volume range: 90-338 mL per breast) and 15 female recreational runners with a medium-large breast size (volume range: 351-1029 mL per breast) were matched for age and body mass index. Kinematic and oxygen consumption (V̇O 2 ) data were collected while participants completed an 8-min treadmill protocol at two incremental velocities (8 and 10 km·h -1 ).

Results: Running economy was not affected by breast volume. Multiplanar breast displacement was significantly greater for larger breast volumes, despite participants wearing a high-support sports bra. A higher breast volume was also associated with less vertical center of mass excursion at velocity of 10 km·h -1 and higher trunk lateral flexion angular velocity at foot flat.

Conclusions: Women with large breast volumes experience significantly more breast motion compared with their smaller breasted counterparts during running, despite the presence of a high-support sports bra. Although increased breast motion as a result of breast size did not translate to differences in running economy, it did alter upper body biomechanical factors known to influence running economy-total body center of mass vertical excursion and peak angular velocity of the trunk in the frontal plane. Future research should explore what effect excessive trunk motion has on the mechanics of the lower limb during running among women across the breast size spectrum, as well as how this may influence neuromuscular control and coordination between the upper and the lower limb during running.