Frontiers in Physiology最新文献

The present paper is a review of the mitochondrial Voltage Dependent Anion Channel (VDAC), popularly known as mitochondrial porin, which is a protein that forms a passive diffusion ion channel across the outer membrane of the mitochondrion. VDAC essentially plays an important role in the transport of metabolites like ATP between the intermembrane space of the mitochondrion and the cytoplasm. However, under certain conditions, it can give rise to cellular dysfunction, e.g., apoptosis. Although VDAC is present in all eukaryotic cells, this review has focused mainly on the animal tissues. Interactions of VDAC with various enzymes, proteins, and small molecules or ligands have been reviewed with a perspective of bilayer electrophysiology. Importantly, the biochemical (post-translational) modifications of the channel protein, namely, phosphorylation (by a series of kinases), acetylation, ubiquitination, oxidative modifications (such as glutathionylation and nitrosylation), etc., and their impact on the electrophysiological properties have been discussed. Finally, the consequences of the above-mentioned experimental findings have been discussed with predictions and hypotheses relevant to living systems.

Background: Falls among older adults represent a major cause of morbidity and mortality, leading to decreased physical activity, loss of independence, and increased dependency. Individuals aged 60 years and older, particularly those with sensory deficits, are at greater risk. While conventional fall-prevention programs are widely implemented, innovative strategies such as active exergames have emerged as promising approaches to enhance balance and reduce fall risk.

Objective: This study aims to evaluate the effectiveness of a supervised exergame-based multicomponent intervention compared to a traditional multicomponent training program in community-dwelling older adults at risk of falling.

Methods: A randomized controlled trial with parallel groups and blinded assessment will be conducted among older adults (≥60 years) recruited from senior centers (SENAMA, Chile). Fifty-two participants will be randomly allocated to either an exergame group (n = 26), performing interactive full-body movements using the Nintendo Switch^®, or a traditional multicomponent training group (n = 26). Both groups will receive 1-h supervised sessions twice weekly for 12 weeks. The primary outcomes will include fall risk, balance performance, functional independence and cardiorespiratory fitness. Secondary outcomes will assess body composition, muscular strength and quality, physical activity level, quality of life, and pain intensity and interference.

Expected results: It is hypothesized that both interventions will improve functional and balance outcomes, with the exergame-based program potentially promoting greater adherence and superior overall effects.

Clinical trial registration: ClinicalTrials.gov. Identifier: NCT07024004.

Prolonged exposure to hypoxia can elevate serum erythropoietin (EPO) and may eventually increase hemoglobin mass. However, whether intermittent hypoxia consisting of breathing short intervals alternated with normoxia (acute intermittent hypoxia; AIH) can trigger erythropoiesis and lead to increases in hemoglobin mass is less clear. Therefore, the purpose of this study was to investigate the effect of consecutive days of AIH on hemoglobin mass. Participants (n = 18) were exposed to 4 consecutive days of AIH consisting of fifteen 90 s intervals of breathing ∼9% O₂ alternating with 60 s of breathing room air (∼21% O₂). Hemoglobin mass was measured in each participant before the first and after the last exposure. In a separate group of individuals (n = 12) we collected serum blood samples for EPO analysis before and 4.5 h after one of the AIH sessions, as well as at the same timeframe on a day with no AIH to serve as control. There was no significant increase in hemoglobin mass after four consecutive days of AIH in the first group with no serum EPO collection, or in the second group for which we collected EPO. Further, there was no significant increase in serum EPO after AIH as compared to control. These results indicate that four consecutive days of AIH is not a sufficient hypoxia exposure to elicit increases in hemoglobin mass in able-bodied individuals. Serum EPO results suggest that a single session of the current acute intermittent hypoxia protocol does not provide enough stimulus for EPO production.

Objective: In this meta-analysis, we aimed to examine the effects of plyometric complex training (PT) on lower-limb explosive power in adolescents and explore the moderating role of different training variables.

Methods: Eight databases, including CNKI, PubMed, and Web of Science, were systematically searched. Studies were screened according to predefined inclusion, exclusion, and quality assessment criteria. Data were analyzed using STATA 17.0 and Review Manager 5.4.

Results: A total of 11 studies involving 311 participants were included. The meta-analysis showed that PT significantly improved countermovement jump (CMJ) height (MD = 2.20, 95% CI: 1.46-2.95, P < 0.00001) and squat jump (SJ) height (MD = 2.13, 95% CI: 1.32-2.94, P < 0.00001). For sprint performance, PT yielded significant improvements in 20-m sprint time (MD = -0.10, 95% CI: 0.18 to -0.01, P < 0.05), whereas the improvement in 10-m sprint performance was not statistically significant. Subgroup analysis indicated that an intervention duration of ≥8 weeks was a key factor for achieving significant effects.

Conclusion: PT is useful in improving lower-limb explosive power in teenagers. For the best results, training programs should consider adolescents' physiological characteristics and use protocols that run for at least 8 weeks, with 2-3 sessions each week, each lasting 20 min-30 min and separated by 1 min-2 min of rest between the sets. The emphasis should be on increasing the jumping ability and short-distance sprint performance.

Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/myprospero, identifier CRD420251149485.

Introduction: We sought to determine if pre-intervention bone characteristics measured by dual-energy x-ray absorptiometry (DXA) were associated with changes in bone-free lean tissue mass following a period of resistance training in a large cohort of untrained adults (n = 119, 62M/57F, 26.0 ± 4.7 kg/m², age range = 18-70 years old).

Methods: Participants completed 10-12 weeks of supervised whole-body resistance training twice weekly, and DXA scans were obtained approximately the same time of day prior to the intervention and 48-72 h following the final training bout. Associations between baseline skeletal measures (e.g., appendicular bone characteristics, shoulder and hip widths) and training induced changes in appendicular lean mass were examined by estimating correlations between participant-level random slopes (reflecting change over time) and baseline skeletal measures. The same approach was used to evaluate associations between other participant attributes (e.g., age, training volume-load, self-reported energy intake) and appendicular lean tissue mass changes. Modeling was also used to explore whether baseline skeletal characteristics (e.g., shoulder and hip widths) moderated the change in appendicular lean tissue mass from training. All analyses used a Bayesian framework, and interpretation focused on estimated effect sizes and their associated credible intervals rather than formal null hypothesis testing.

Results: Strong positive associations were observed between pre-intervention characteristics including dual-arm lean tissue mass and dual-arm bone mineral content (r = 0.90), dual-leg lean tissue mass and dual-leg bone mineral content (r = 0.86), dual-leg lean tissue mass and pelvic mineral content (r = 0.73), and dual-arm lean tissue mass and shoulder width (r = 0.76). In contrast, weak associations were observed between training-induced changes in appendicular lean tissue mass versus bone characteristics, training volume-load, self-reported energy intake, self-reported protein intake, BMI, and age (-0.08≤r ≤ 0.24). After adjusting for sex, multivariable analyses indicated minimal evidence that skeletal characteristics moderated the hypertrophic response to training.

Discussion: These provide limited evidence suggesting pre-training bone characteristics do not influence lean tissue mass adaptations to shorter-term resistance training.

Heat stroke is a severe, life-threatening medical emergency defined by an elevation in core body temperature exceeding 40.0 °C, accompanied by acute central nervous system (CNS) dysfunction and often complicated by multi-organ failure. Although traditionally viewed as a thermoregulatory collapse from environmental exposure or intense exertion, recent evidence highlights its complex, multifactorial pathophysiology. This includes systemic inflammation, immune dysregulation, oxidative stress, endothelial injury, and activation of the coagulation cascade. This comprehensive narrative examines advances in understanding underlying mechanisms, clinical manifestations, emerging biomarkers, and outcomes in both classic (non-exertional) and exertional heat stroke. Emphasis is placed on the gut-brain axis, where disruption of intestinal barrier integrity and microbiota dysbiosis amplify systemic inflammation and contribute to neurotoxicity. Heat stroke-related neurological damage affects critical brain regions, including the hypothalamus, cerebellum and hippocampus, often resulting in long-term cognitive and motor impairments. Several biomarkers that include interleukin-6 (IL-6), high-mobility group box 1 protein (HMGB1), creatine kinase (CK), S100β, and D-dimer are under active investigation for diagnostic and prognostic utility, but their clinical use remains limited by inter-individual variability and lack of standardized thresholds. Recent advances in artificial intelligence (AI) and wearable biosensors may facilitate early detection, continuous monitoring, and individualized risk prediction, particularly in vulnerable populations such as outdoor workers, athletes, and military personnel. An interdisciplinary approach is critical to improving early recognition, management strategies, and long-term outcomes in the context of rising global temperatures and climate change.

Background: Weightlifting (WT) and Plyometric training (PT) may lead to comparable enhancements in strength, jump, and sprint performance. However, these two training modalities appear to differ significantly in their primary focus and underlying mechanisms.

Objective: Examining the differences between WT and PT in improving lower extremity sports performance.

Methods: A systematic search was conducted from five databases, including Web of Science, PubMed, Scopus, Elsevier, and Springer. Two authors developed specific inclusion and exclusion criteria to screen relevant literature based on the study objectives. The quality of the included studies was assessed using the Physiotherapy Evidence Database (PEDro) scale. We conducted both direct comparisons and network meta-analysis on the eligible studies. The assumptions of similarity, homogeneity, and consistency within the Bayesian network were also confirmed.

Results: A total of 17 studies met the inclusion criteria, involving 394 participants. All studies were found to have a low or moderate risk of bias, with average score of 4.29. The Bayesian network meta-analysis showed no significant differences. According to the SUCRA rankings, TT was most likely to excel in squat jumps (SJ) (SUCRA = 0.76) and maximum strength (SUCRA = 0.95), WT for sprint (SUCRA = 0.77), and PT for countermovement jumps (SUCRA = 0.76). The tests of similarity, homogeneity and consistency of the network meta-analysis were also generally valid. The funnel plot and Egger regression tests indicated no publication bias.

Conclusion: In summary, the WT programs are more effective at improving sprint performance by increasing power, while the PT programs improve jumping performance by improving the stretch-shortening cycle.

Systematic review registration: identifier CRD 420250540130.

Background: Advanced footwear technology (AFT) is reported to elicit an approximate 4% average improvement in running economy (RE). However, a large inter-individual variability remains unexplained, and limited research examined the impact of AFT during outdoor running. The aim was to compare the physiological, biomechanical and perceptual responses of 36 well-trained athletes to running outdoors using three different AFT and a traditional racing shoe.

Methods: Thirty-six well-trained athletes (19 males and 17 females) had their maximal aerobic capacity ( $\dot{V}$ O₂max) and anaerobic threshold (AT) determined in laboratory conditions and were familiarised to the different shoe running conditions. Within 7 days, athletes ran 4 × 6 min running bouts, paced outdoors at 95% of their individual AT with 10 min recovery, in three different AFT conditions and a traditional flat. Oxygen uptake ( $\dot{V}$ O₂), heart rate, rating of perceived exertion (RPE), lactate, shoe perception, and biomechanical responses were compared between the four running trials.

Results: No differences were observed in the RE between shoe conditions, with a great inter-individual variability (range: 12% impairment to 14% improvement in RE). This variability was accompanied by a significant $\dot{V}$ O₂ order effect across exercise bouts (bout 2 lower than one [-1.1 mL/kg/min, p = 0.002]; bout 3 lower than 2 [-0.8 mL/kg/min, p = 0.027]; no differences between bouts 3 and 4). This variability was likely due to methodological issues such as one squared-wave RE measurement per shoe condition or the lack of a mirrored experimental design, among others. There was no order effect in other physiological or biomechanical variables. No significant differences were found in lactate, heart rate or rate of perceived exertion between running trials. Biomechanical responses to the different shoe conditions were also highly variable. One of the advanced AFT shoes showed a greater strike angle (+2.07°; p = 0.001), with no other significant differences between shoes conditions.

Conclusion: The large variability in the physiological response to AFT may be explained by methodological considerations. A minimum of two-bout RE measurements, the use of a mirrored order, a sufficient familiarisation with shoes and experimental designs, among other considerations, seem crucial to enhance the ecological validity and reduce data variability.

Background: Multifocal transcranial direct current stimulation (m-tDCS) may modulate distributed motor networks in a polarity-dependent and task-state-dependent manner to support performance near exhaustion. To this end, this study aims to test whether m-tDCS targeting lower-limb-specific cortical areas could optimize late-stage performance and phase-specific muscle coordination during cycling.

Methods: Two independent trials were conducted: (i) a tolerability assessment (Trial 1) and (ii) a randomized, double-blind, sham-controlled parallel study (Trial 2). In Trial 1, participants completed the tolerability test and recorded pain and side effects during a 21-min stimulation period. In Trial 2, healthy adults completed an incremental cycling test; late-stage performance was operationalized a priori as the 85%-100% peak power output (PPO) phase, during which the time-to-exhaustion (TTE), work (W), mean power (P), revolutions per minute (RPM), heart rate (HR), blood lactate level (ΔL), ratings of perceived exertion (RPE), and EMG-derived muscle contribution ratio (MCR) and knee co-activation index (CAI) were analyzed across propulsion and pull.

Results: (1) m-tDCS was well-tolerated; pain ratings declined progressively across the stimulation, with typical transient sensations. (2) At the 85%-100% PPO phase, m-tDCS increased W and RPM relative to sham without altering the mean power or ΔL; HR decreased after m-tDCS, and RPE rose only after sham. (3) At the coordination level, m-tDCS preserved quadriceps MCR during propulsion and reduced antagonistic activation during pull to prevent the CAI increase observed in the sham.

Conclusion: m-tDCS did not augment peak mechanical output but preserved late-stage endurance via phase-specific coordination tuning, which is consistent with improved neural efficiency near exhaustion. These findings refine mechanistic interpretations of the effects of tDCS on endurance and support m-tDCS as a safe, coordination-centric adjunct for high-intensity cycling.