International journal of exercise science最新文献

High-incline walking is a popular mode of exercise and often serves as an alternative to level-grade running for improving cardiovascular fitness. This study examined the muscle activation and biomechanical differences between high-incline walking (HIW) at a 20% grade and level-grade jogging (LGJ) at matched exercise intensities. Nineteen physically inactive adults (18-31 years) participated. Participants completed two isocaloric exercise trials (HIW and LGJ), each lasting ten minutes. EMG data were obtained from eight muscles: biceps femoris (BF), gluteus maximus (GM), lateral gastrocnemius (LG), tibialis anterior (TA), vastus lateralis (VL), anterior deltoid (AD), erector spinae (ES), and soleus (SOL). Resultant accelerations on the foot and sacrum were measured using inertial measurement units (IMUs). At matched isocaloric intensities between LGJ and HIW, mean peak resultant acceleration was significantly higher in LGJ for the foot (22.14 ± 8.44 m/s²) and sacrum (27.21 ± 7.92 m/s²). Peak EMG activation was significantly greater during LGJ in TA (40.9% ± 21.4) and VL (52.6% ± 39.8). The EMG integral was significantly greater in the LGJ for the TA (13.8% ± 5.0) than during HIW. Despite being matched isocalorically, LGJ increased peak and integral muscle activation and produced higher foot and sacrum accelerations. These findings highlight HIW as a lower-impact, yet equally demanding, alternative to LGJ, with implications for exercise prescription and injury prevention.

Isometric handgrip (IHG) coupled with post-exercise muscular ischemia (PEMI) and the cold pressor test (CPT) have been demonstrated to increase measures of hemodynamics and to reduce vagal tone. However, little is known about how acute resistance exercise (RE) alters these responses. The purpose was to evaluate an acute bout of RE in conjunction with a single- or dual-stressor task on hemodynamics and autonomic modulation in resistance-trained individuals. Ten resistance-trained individuals (Mean ± SD; Age: 23 ± 3 years) completed a single-(SS: IHG + PEMI only) or dual-stressor (DS: IHG + PEMI + CPT) task condition. Before and after the acute RE variables were monitored during five minutes of rest (REST), two minutes of IHG, three minutes of PEMI with or without concurrent CPT (STRESS). Hemodynamics included heart rate (HR), mean arterial pressure (MAP), cardiac output (Q,). stroke volume (SV) and total peripheral resistance (TPR), while autonomic data were measured via heart rate variability and heart rate complexity. There were no significant (p > 0.05) three-way interactions for HR, Q, or TPR. However, there was a significant three-way interaction (p = 0.007) for SV such that SV was significantly increased during STRESS compared to REST in the SS condition but did not change in the DS condition. There were no significant (p > 0.05) interactions for measures of autonomic modulation. These data suggest that young, resistance-trained individuals have a significant cardiac sympathetic reserve and thus a large capacity to handle multiple stressors following acute RE.

We investigated the effects of a new approach with mixed session periodization resistance training (MSP) on functional performance, muscular strength, and body composition in older women. Twenty-one participants were tested before and after the intervention (10 weeks) and were allocated for convenience into two groups according to their available time; our schedule made two classes available, one at 6 a.m. (MSP), and one at 7 a.m. (active group-control). Results were analyzed through a mixed-model analysis with repeated measures. There was a group vs. time interaction for timed up and go (p < 0.001, η_p ² = 0.478; MSP: pre = 8.2 ± 1.3s, post = 7.1 ± 1.1 s; CON: pre = 7.8 ± 1.2s, post = 7.6 ± 1.1 s), stair ascent (p = 0.001, η_p ² = 0.478; MSP: pre = 12.5 ± 2.1s, post = 10.8 ± 1.9s; CON: pre = 12.3 ± 2.0s, post = 12.1 ± 1.8s), and stair descent tests (p < 0.001, η_p ² = 0.579; MSP: pre = 13.2 ± 2.3s, post = 11.4 ± 2.0s; CON: pre = 12.9 ± 2.2s, post = 12.7 ± 2.1s). There was also a group vs. time interaction for concentric knee extension (p = 0.001, η_p ² = 0.465; MSP: pre = 120.5 ± 18.7 Nm, post = 135.6 ± 20.1 Nm; CON: pre = 118.3 ± 17.9 Nm, post = 119.8 ± 18.2 Nm), and for bench press (p < 0.001, η_p ² = 0.635; MSP: pre = 25.3 ± 4.5 kg, post = 30.1 ± 5.0 kg; CON: pre = 24.8 ± 4.3 kg, post = 25.2 ± 4.4 kg), lat pulldown (p = 0.005, η_p ² = 0.345; MSP: pre = 30.2 ± 5.1 kg, post = 35.0 ± 5.6 kg; CON: pre = 29.8 ± 5.0 kg, post = 30.1 ± 5.1 kg), deadlift (p < 0.001, η_p ² = 0.606; MSP: pre = 45.6 ± 7.2 kg, post = 52.3 ± 7.8 kg; CON: pre = 44.9 ± 7.0 kg, post = 45.3 ± 7.1 kg), and squat (p < 0.001, η_p ² = 0.694; MSP: pre = 40.5 ± 6.8 kg, post = 47.2 ± 7.5 kg; CON: pre = 39.8 ± 6.7 kg, post = 40.1 ± 6.8 kg). There were no significant changes in body fat percentage, absolute body fat, or lean mass. Our findings demonstrated that independently of sequence, the mixed session periodization model resulted in increased muscle strength and functional capacity in aging adults, but no significant changes in body composition were observed.

The conflation of sex and gender in sport and exercise science research has led to gaps in representation and understanding of gender-inclusive outcomes. This invited editorial presents a framework to guide researchers in conducting statistical analyses that account for multiple gender identities beyond the traditional binary classification. The invited editorial guides deliberation on whether to test for sex or gender differences in sport or exercise science research. It prompts investigators to answer the question, "Is there a valid, literature-supported rationale for investigating sex or gender differences?" If "yes", we propose approaches that may help investigators plan a study for two sex or gender groups, or in situations with three or more sex or gender groups. The editorial provides a valid, step-by-step statistical decision framework to ensure a robust, and ethical, research design while addressing the limitations of current sex- and gender-based classifications in sport and exercise science. By adopting gender-inclusive research practices, the field can better support equitable exercise prescriptions, rehabilitation strategies, and training periodization for diverse populations.

Low energy availability (LEA) results in numerous health and performance decrements. While a high prevalence of LEA and sleep disturbance has been observed in male Army Reserve Officers' Training Corps (ROTC) cadets, no data exists in females. This study aimed to determine LEA prevalence, dietary habits, and sleep quantity and quality in female U.S. ROTC cadets. Following an overnight fast, ten cadets (22±4 yrs, 166.0±6.1 cm, 67.1±9.1 kg, 26.1±6.2% body fat, 49.2±4.8 kg fat-free mass (FFM)) had their body composition and resting metabolic rate measured. Validated questionnaires assessed LEA symptoms and sleep. Under free-living conditions, exercise energy expenditure (EEE) and sleep were quantified via accelerometers for 7-days. Concurrently, energy intake (EI) was assessed via digital food records and evaluated relative to the Military Dietary Reference Intakes (MDRIs). Cadets consumed 1983±706 kcal·d^-1 with a mean EEE of 482±110 kcal·d^-1. EA was 30.6±13.2 kcals·kg^-1 FFM with 40% presenting with LEA (≤ 30 kcals·kg^-1 FFM) and another 50% in a suboptimal EA state (30-45 kcals·kg^-1 FFM). Dietary analysis indicated 30%, 40%, 80%, and 10% of cadets met MDRIs for calories, carbohydrate, protein, and fat, respectively. Cadets slept 373±100 min·d^-1, with 20% of cadets meeting the Army recommendation for sleep. Sleep questionnaires indicated that 60% of cadets experienced poor sleep quality and 30% had poor sleep behavior. In the present study, all but one cadet was in a low or suboptimal EA state, a high prevalence of sleep disturbance was observed, and most cadets did not meet MDRIs for energy and macronutrient intakes.

The study investigated the effects of a quadriceps-dominant (QD) versus functional (FX) training program on the Functional Movement Screen (FMS), activities of daily living (ADLs), and motor unit (MU) recruitment of the vastus lateralis (VL) and biceps femoris (BF). Twenty-six older adults (68.9 ± 5.1yrs) were randomly assigned to a 6-week QD or FX training program. Participants completed ADLs, FMS, and three closed-kinetic chain exercises (CKCs): front lunge (FL), side lunge (SL), and bilateral squat (BLSQ), pre and post-intervention. Electromyography was recorded from the VL and BF during maximal voluntary isometric contractions (MVICs) and CKCs. Raw EMG recordings during CKCs were normalized to MVICs, and analyzed for root mean square (RMS). The QD program resulted in improved FMS performance during a deep-squat (p = 0.003), in-line lunge (p = 0.013), and hurdle step (p = 0.034), as well as improved ADL sit-to-stand (STS) and STAIRS (P < 0.05). Furthermore, the QD program resulted in greater RMS of the VL during CKCs (p < 0.05). Lastly, a positive correlation was observed between ADLs and RMS of the VL (p < 0.05, r > 0.6), whereas negative correlations were observed between FMS movements and RMS of the BF (p < 0.05, r < -0.6). The results suggest that a QD program may lead to greater improvements in functional movements, ADLs, and VL MU recruitment compared to a FX program. Additionally, MU recruitment of the VL is essential for functional ability, whereas high MU recruitment of the BF may coincide with reduced functional ability. The results of this study suggest that QD training may improve functional abilities in older adults.

Carbon-fiber shoes feature a stiff yet lightweight curved carbon-fiber plate embedded in the sole and a resilient midsole foam. These shoes create spring-like rebounding effect that has proven to decrease energy consumption and enhance athletic performance. To date, most biomechanics research on carbon-fiber shoes has been laboratory-based. The purpose of our study was to compare running biomechanics in competitive runners wearing carbon-fiber shoes or traditional shoes using wearable sensors on an outdoor composite track. Ten elite runners (9F, 1M) who consistently ran over 30 miles per week and owned a pair of carbon-fiber shoes participated. The experiment consisted of three 40-meter run trials in carbon-fiber shoes and three trials in traditional running shoes. The self-selected speed was held constant between the two conditions. Two Inertial Measurement Units (IMUs) were strapped on subject's right foot and tibia to measure biomechanical parameters including tibial acceleration, eversion velocity, stance time, stride frequency, sagittal plane angular velocity of the foot at toe-off, and sagittal plane angular acceleration of the foot during propulsion. A paired sample t test was used to compare between shoe conditions. Sagittal plane angular acceleration of the foot during propulsion was significantly greater in the carbon-fiber shoes, 8774.4±4348.2 deg/sec ², compared to 7492.9±3495.0 deg/sec ² for traditional shoes (P=0.01, Cohen's d=0.513). Additionally, sagittal plane angular velocity of the foot at toe-off approached significance (carbon-fiber: 953.1±227.9deg/sec, traditional: 881.0±216.1deg/sec, P=0.082, Cohen's d=0.326). No other differences were noted. Carbon-fiber shoes create a more efficient toe-off by providing greater propulsive acceleration during push-off.

Acute ankle sprains are common in sports and carry a significantly increased risk of recurrence after an initial injury. Bracing has been shown to reduce injury recurrence; however, athletes may decline this prophylactic measure due to fear of negative effect on athletic performance. Previous research examining the impact of bracing on performance has demonstrated conflicting results. The purpose of this study was to examine the effect of bracing on choice reaction time and foot speed in healthy, young adults using computerized agility testing. Twenty-eight healthy athletes aged 18-25 years completed the study. Subjects performed testing for choice reaction time (CRT), foot speed-forward (FSF), and foot speed-backwards (FSB) using Quick Board technology. Testing was performed in 3 bracing conditions: non-braced (NB), braced dominant ankle (BD), and braced non-dominant ankle (BND). Separate repeated ANOVAs were used to compare the effect of bracing for each performance variable. No significant effect of bracing on CRT (p=0.95) or FSF (p=0.075) was observed; however, there was a significant effect on FSB (p=0.035). Post-hoc testing revealed foot speed in the backwards direction was significantly lower in the BND condition vs. the NB condition (p=0.029). While bracing does not significantly impact CRT or FSF, bracing the non-dominant ankle may limit performance in athletic tasks that require posterior movement. These results provide valuable insights for clinicians and athletes when weighing the benefits of prophylactic bracing against the potential negative impact on performance.

The total work completed during an exercise session is often assumed to be the primary factor influencing the kinetics of post-exercise recovery. However, the duration of work and rest periods during high intensity interval training (HIIT) have been shown to impact the magnitude of physiological stress and could also impact post-exercise recovery. The aim of this study was to characterize the recovery time course of neuromuscular function following work-to-rest matched HIIT protocols with different work interval durations and conducted to task failure. Participants (n=12, n=6 females) completed a ramp incremental exercise test to determine peak power output (PPO). In a randomized order, participants completed 3 cycling protocols at 90% PPO: (i) 3 min work, 3 min passive rest HIIT (HIIT_3min), (ii) 1 min work, 1 min passive rest HIIT (HIIT_1min), and (iii) constant load (CL) cycling. Femoral nerve electrical stimuli during maximal voluntary contractions (MVC) of isometric knee extension were performed at baseline, task failure (TF), and TF+1min, TF+4min, and TF+8min to delineate the time course of neuromuscular function recovery. MVC force declined to the same level following the three conditions at TF and demonstrated a partial recovery within TF+8min (time effect: P<0.001). The evoked muscle twitch force declined more following the CL compared to HIIT_1min at TF (P = 0.013) and showed a faster recovery within TF+8min (P<0.024). Voluntary activation decreased at TF in the HIIT_1min but not in HIIT_3min or CL (interaction effect: P<0.023) and fully recovered within TF+8min. Central and peripheral components of neuromuscular function demonstrate distinct time courses of recovery between CL exercise and work:rest matched HIIT protocols with different work interval durations.

Military personnel face rigorous physical and cognitive demands critical for operational readiness and long-term health. This study evaluated body composition, cognitive performance, and physical fitness metrics in non-entry-level service members to inform tailored fitness interventions. This cross-sectional study analyzed data from Air Command Staff College personnel (N = 307; 89 females, 218 males; age: 37 ± 5 years) at Air University, Maxwell Air Force Base. Participants completed assessments for body composition (body mass index [BMI], body fat percentage [%BF], fat mass index [FMI], fat-free mass index [FFMI]), flexibility (sit-and-reach test, functional reach test), cognitive performance (cognitive reaction time), power (countermovement jump), strength (grip strength, isometric midthigh pull), muscular endurance (plank), and aerobic fitness (Estimated VO_2max). Relationships between age, sex, and fitness variables were analyzed with regression models, with percentile ranking, and comparisons to the American College of Sports Medicine (ACSM) guidelines. Age-related increases in BF% (r = 0.116, p = 0.045) and FMI (r = 0.129, p = 0.025) were observed, alongside declines in muscular strength, power, and endurance (all p < 0.01). Females exhibited higher BF% and FMI, while males had greater FFMI and strength. Older participants had lower compliance with ACSM standards, indicating elevated health risks. Targeted interventions should address age- and sex-specific needs, focusing on preserving lean mass, strength, and cognitive agility. Baseline fitness data contributes to designing evidence-based programs that enhance long-term readiness and operational performance.