European Journal of Applied Physiology最新文献

Objectives: The purpose of this study was to compare the effects of a 14-day daily ischemic preconditioning (IPC) intervention versus a sham IPC intervention on microvascular post-occlusive hyperemic reactions and quadriceps muscle morphology in martial arts athletes.

Design: This randomized controlled trial involved 28 adults specializing in martial arts, who were randomly assigned to either the IPC or sham IPC group.

Methods: Participants in the IPC intervention completed two daily sessions over 14 consecutive days. Each session consisted of three cycles of 5 min of 100% arterial occlusion pressure (AOP) followed by 5 min of rest, for a total session duration of 30 min. Assessments were conducted at baseline, immediately after the 14-day intervention (afterInt), 7 days post-intervention (7d-afterInt), and 2 weeks post-intervention (2w-afterInt). The measured outcomes included peak isometric strength, rate of force development (RFD), pennation angle at rest (PA rest) and during maximal contraction (PA contraction), resting blood flow (RF), minimum and 100% AOP, biological zero (BZ), reactive hyperemia (RH max), time to peak maximal perfusion (TP), recovery time for perfusion to return to resting values (TR).

Results: Significantly higher RFD values in IPC afterInt (p = 0.005) as well as RF values (p = 0.014) were found. Significantly higher BZ values in IPC afterInt (p < 0.001) as well as 7d-afterInt (p < 0.001) were also found.

Conclusions: This study suggests that the significant positive effects of IPC, compared to shamIPC, on strength and perfusion parameters persist for up to 7 days after the intervention.

Purpose: Trail running poles are widely used among trail runners but their effects on cost of transport and biomechanics under fatigued conditions remains understudied. This study aimed to evaluate the effects of pole use on the walking vertical cost of transport (CoT_vert) and foot force (FF) before and after a simulated trail running competition (STRC).

Methods: Sixteen trail runners ( ${\dot{\text{V}}\text{O}}_2$ : 61.0 ± 8.3 ml/kg/min; ITRA performance index: 634 ± 107 points) performed walking trials with (PW) and without poles (CW) on an incline treadmill (18.6 degrees) before (PRE) and after (POST) a STRC. The course covered 31.2 km with 2086 m of elevation gain and was completed under race-simulated conditions. CoT_vert and FF were measured using instrumented insoles, and axial pole force was recorded during PW.

Results: The STRC was completed in 4:25:33 ± 0:39:51 (hh:mm:ss) at an average heart rate (HR) of 81.4 ± 3.8% of HRmax. Walking CoT_vert showed significant time and condition effects, with higher values without poles at POST (+ 2.50 ± 2.62%, p = 0.0183). Rating of perceived exertion (RPE) was lower with poles at both PRE and POST (p = 0.0022 and p = 0.0187, respectively). FF was significantly lower with poles at PRE (p = 0.0140) and POST (p < 0.0001). Poling force decreased at POST compared to PRE (p = 0.0026).

Conclusions: The main findings are that (1) CoT_vert increases after STRC; (2) walking CoT_vert and FF are lower with pole use and (3) upper limb force decreases at POST. These results support the use of poles in long-lasting events to reduce CoT, redistribute workload and possibly mitigate the fatigue effects.

Introduction: Neuromuscular electrical stimulation (NMES) is used as a rehabilitation technique for individuals with physical function limitations and mobility impairments. However, the potential for NMES-induced muscle contraction to improve metabolic health is unclear. This study investigated the effect of NMES on glycemic control and energy expenditure in a predominantly Hispanic population.

Methods: Overweight/obese participants with hyperglycemia (N = 56 [Males: 19; Females: 37] Age: 33.3 ± 11.8 years; BMI: 34.8 ± 5.6 kg/m²) underwent 30 min of NMES on both quadriceps muscles after an overnight fast. Glucose levels were continuously measured for over 48 h, encompassing the stimulation day and a control day, using a continuous glucose monitor. Standardized eucaloric diet was provided on both days. Energy expenditure and substrate utilization were measured by indirect calorimetry before and during the NMES application.

Results: Thirty minutes of NMES treatment reduced glucose levels compared to baseline glucose (116.2 ± 2.7 mg/dL to 113.2 ± 2.5 mg/dL; p < 0.0001). Glycemic control determined by 24-h glucose variability/fluctuations was significantly lower on the day of NMES compared to the control day (18.0 ± 1.0 mg/dL vs 20.0 ± 1.2 mg/dL; p < 0.05). Energy expenditure (18.8 ± 0.3 kcal.Day^-1.Kg^-1 to 19.0 ± 0.3 kcal.Day^-1.Kg^-1; p < 0.05) and respiratory exchange ratio (0.79 ± 0.01 to 0.80 ± 0.01; p < 0.05) increased during stimulation compared to the baseline.

Conclusion: Acute application of NMES results in improvement in glycemic control and energy expenditure in the short term. Future studies are needed to determine if chronic NMES-induced muscle contraction can provide an alternate strategy to manage hyperglycemia.

Clinical trial registration: NCT03947697 May 2019.

Purpose: To investigate whether mental fatigue induced by psychological tasks during whole-body surface cooling influences subsequent endurance exercise performance and whether subjective fatigue is associated with performance variability and neuroendocrine responses.

Methods: Nine young adults participated in two trials: a mental stress (MS) trial involving the Stroop test (500 stimuli/set × 2) and a control (CON) trial involving watching a video. Both were conducted during whole-body surface cooling using a water-perfused suit (10 °C, 10 min, then 15 °C, 85 min). The time to exhaustion (TE) during cycling at 80% peak oxygen uptake was evaluated. Chalder's fatigue score (CFS), plasma adrenaline ([Ad]_p), noradrenaline ([Norad]_p), and cortisol ([Corti]_p) concentrations were measured before and after intervention and exercise.

Results: After the intervention, the CFS increased in the MS trial, but not in the CON trial. [Ad]_p and [Norad]_p remained unchanged after the intervention and increased after exercise in both trials, and an increase with exercise was prominent in the MS trial. [Corti]_p remained unchanged. TE decreased by 5.7% in the MS trial. However, this was not statistically significant. The difference (Δ) in TE between trials was significantly negatively correlated with ΔCFS (r = - 0.919, P = 0.002). ΔCFS was significantly positively correlated with Δ[Norad]_p (r = 0.795, P = 0.010), while not with [Ad]_p or [Corti]_p.

Conclusion: Mental fatigue accompanied by whole-body surface cooling variably influences subsequent endurance exercise performance with decrements associated with greater subjective fatigue and heightened sympathoadrenal-medullary activity though trial-level effects were not significant. There was no apparent hypothalamic-pituitary-adrenal axis involvement.

Aim: Skeletal muscle blood volume responds to the metabolic demands of exercise and augmented microvasculature reactivity. We sought to explore the effects of exercise intensity (maximal vs. submaximal) on near-infrared spectroscopy (NIRS)-derived blood volume and microvascular reactivity in the acute post-exercise timeframe.

Methods: Healthy individuals (N = 18) between 18 and 35 years completed a vascular occlusion test (VOT) followed by a maximal cycling test. A second VOT was performed 15-min post-exercise. One week later, the protocol was repeated before and after a submaximal bout of cycling (60% VO₂ peak). NIRS was used to assess total hemoglobin (tHb) (i.e., blood volume) before, during, and after exercise, as well as muscle oxygen consumption (mVO₂) and microvascular reactivity (StO₂% s^-1) pre- and post-exercise.

Results: Compared with pre-exercise, tHb was elevated at the end of exercise (p < 0.001) and remained elevated 15-min post-exercise (p < 0.001) regardless of trial (combined means pre: 5.39 ± 0.82, during: 14.01 ± 1.73, and post-exercise: 10.89 ± 1.24 O.D.). mVO₂ was greater post-exercise in the max vs. submax trial (- 0.36 ± 0.12 vs. - 0.22 ± 0.11% s^-1; p < 0.001). Compared with pre-exercise, microvascular reactivity was unchanged following the max trial (1.91 ± 0.61 vs. 1.71 ± 0.61% s^-1; p = 0.079) but was greater following the submax trial (1.72 ± 0.43 vs. 1.98 ± 0.59; p = 0.007).

Conclusion: Cycling at a submaximal, but not maximal, intensity results in augmented post-exercise microvascular reactivity, while post-exercise increases in skeletal muscle blood volume were found regardless of exercise intensity.

Purpose: Liuzijue, a traditional Chinese Qigong, is effective for respiratory rehabilitation, yet its underlying mechanisms remain largely theoretical due to complex movement patterns. This study aimed to record respiratory muscle surface electromyography (EMG) during Liuzijue practice, analyze muscle activation characteristics, and provide a scientific basis for its clinical application.

Methods: Thirty-two proficient Liuzijue practitioners underwent calm breathing, deep breathing, and Liuzijue training with surface EMG recordings. Contraction strength, duration, recruitment sequence of respiratory muscles, and physiological parameters (heart rate, perceived exertion, oxygen saturation) were analyzed across the three phases.

Results: Compared to calm breathing, Liuzijue significantly increased activation of external intercostal muscles, diaphragm, rectus abdominis, and transversus abdominis. During Liuzijue, internal oblique and multifidus activation was higher than during deep breathing. The activation state of the tested respiratory muscles was also influenced by the different movements within Liuzijue. Liuzijue also extended the contraction time of certain muscles and adjusted the activation sequence of transversus abdominis and external oblique muscles. Heart rate during Liuzijue was consistent with low-intensity exercise, with no significant differences in perceived respiratory fatigue or oxygen saturation compared to the other phases.

Conclusion: As a low-intensity exercise, Liuzijue enhances respiratory muscle activation, extends contraction duration, and adjusts activation sequence, supporting its clinical application in respiratory rehabilitation.

Trial registration: The study was registered with the China Clinical Trial Registry on July 26, 2024 (No. ChiCTR2400087442).

Background and objective: Heat acclimation is a common strategy for athlete preparing to compete in the heat. It is generally obtained by exercising in a hot environment, (e.g. environmental chambers) but passive exposure to hot water has also been shown to induce acclimation. Thus, combining exercise in hot water could be an innovative method to enhance performance in hot environments.

Methods: In this prospective randomized controlled trial, two groups of 12 participants (22 males/2 females) underwent 10 aerobic training sessions on an underwater bike in either hot (35 °C-hot water acclimation, HWA) or temperate (25 °C, control, CON) water. Two to three days before and after intervention participants performed a 30-min time trial, in a hot and humid environment (T°: 38.4 ± 1.4 °C, Relative Humidity: 45.3 ± 6.9%), as well as a cardiac echography, a blood analysis and a cardiopulmonary exercise test (V̇O_2max) in temperate ambient conditions.

Results: The distance covered during the time trial in the heat increased depending on group (p = 0.024) with an increase of 1.1[+ 0.7, + 1.4]km in HWA (p < .001) and 0.5[+ 0.1, + 0.8]km in CON (p = 0.009). As well as power output (p = 0.096) improved more in the HWA vs. CON group (+ 27W in HWA and + 13W in CON). However, no difference between groups was observed regarding changes in physiological parameters during the time trial in the heat (core and skin temperature, sweat rate) or across the tests and measures in temperate environments (plasma volume, heart rate, V̇O_2max).

Conclusion: Exercise on a bike in hot water improves performance in hot and humid conditions but does not induce change physiological parameters in ambient conditions.

Clinicaltrials: gov Identifier: NCT05727774.

Purpose: To investigate age-related differences in motor unit (MU) activation patterns in females during submaximal knee extensions.

Methods: Fourteen young women (22.1 ± 1.5 yrs) and 10 girls (9.8 ± 0.8 yrs) participated in the study. Following the determination of maximal strength (MVC), participants completed trapezoidal isometric contractions to 70%MVC and sEMG was recorded from the vastus lateralis. sEMG signals were decomposed, and MU firing rate (MUFR) and recruitment threshold (RT) were calculated. Group differences in MU activation patterns were assessed using multilevel modelling.

Results: Girls' MVC was significantly lower than young women's, even after accounting for body size (2.0 ± 0.4 and 2.6 ± 0.8 Nm/body mass, respectively). The y-intercept of the MUFR-RT relationship was significantly lower in girls compared with the young women (estimate = 4.38pps; p < 0.05). There were no group differences in the MUFR-RT slope, reflecting lower MUFR in girls among low and high-threshold MUs. Lastly, the highest RT at which MUs were identified was significantly (p = 0.04) lower in girls (53.4 ± 7.2%MVC) compared with young women (60.5 ± 8.2%MVC). Overall, girls had lower MUFR and recruited their MUs over a smaller range of RTs compared with women.

Conclusions: Together, these results suggest that girls and young women utilize different MU activation schemes when performing high-intensity knee extensions. Specifically, compared with women, girls may have to recruit more MUs over a narrower recruitment range due to their lower MUFRs.

Purpose: The use of blood flow restricted (BFR) running may provide an alternative to lower the running speed without compromising physiological responses that often occur during high intensity running. The purpose of this investigation was to compare the acute effects of various submaximal treadmill running speeds with BFR relative to maximal treadmill running speed without BFR on surface electromyographic amplitude (sEMG_AMP), surface electromyographic mean power frequency (sEMG_MPF), and muscle tissue oxygenation (StO₂) responses.

Methods: Thirteen college-aged females randomly completed four, three-minute treadmill running bouts at 70%, 80%, and 90% of their top speed (achieved during a graded exercise test) with BFR (70%_BFR, 80%_BFR, and 90%_BFR) and 100% of their top speed without BFR (100%_NOBFR). The sEMG_AMP, sEMG_MPF, and StO₂ responses were analyzed from the final minute of the treadmill running bouts.

Results: Each treadmill running bout led to similar (zero present in each Bayesian 95% high-density interval) sEMG_AMP, sEMG_MPF, and StO₂ responses (70%_BFR = 80%_BFR = 90%_BFR = 100%_NOBFR). The mean difference (Mean_diff) between speeds ranged from 2.73% to 11.20% for sEMG_AMP, 0.04% to 7.08% for sEMG_MPF, and 0.02% to 1.03% for StO₂.

Conclusion: Despite reductions in treadmill running speed, sEMG_AMP, sEMG_MPF, and StO₂ responses were similar among non-BFR maximal treadmill running and submaximal treadmill running with BFR. Thus, submaximal treadmill running with BFR may serve as a potential alternative when maximal intensity aerobic exercise is contraindicated.