Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme最新文献

A diet of low quality has profound repercussions on health and healthcare costs. Canada has implemented several policies to shift population dietary intakes. Yet, monitoring - an essential component of policy implementation - has been undervalued in Canada's nutrition and health policy, with only two comprehensive national nutrition-focused surveys in the last 50 years. This commentary calls on the Canadian government to implement continuous nationally representative dietary intake monitoring. We demonstrate the importance of dietary intake surveillance for informing evidence-informed nutrition policy. Investments in nationally representative dietary intake monitoring are essential for impactful policies that lead to a healthier Canada.

Background: Metabolic flexibility - the ability to adapt substrate utilization to availability - is commonly impaired in individuals with obesity. While short-term fasting promotes lipid utilization, it may lead to subsequent metabolic inflexibility by blunting carbohydrate metabolism upon refeeding. However, the extent to which this differs in obesity remains unknown.

Objective: To examine if a 48-hour fast differentially affects substrate utilization during refeeding in individuals with and without obesity.

Methods: Adults classified as lean (n = 16) or with obesity (n = 16) (8 males and 8 females per group) completed a 48-hour fast followed by a mixed meal tolerance test (MMTT). Respiratory exchange ratio (RER), glucose, β-hydroxybutyrate (BHB), insulin, and free fatty acid (FFA) levels were measured at baseline, after 48-hours of fasting, and 1 and 2 hours postprandially to assess substrate utilization.

Results: Individuals with obesity exhibited baseline hyperinsulinemia despite similar glucose levels when compared to lean individuals. Fasting reduced circulating insulin and glucose, and elicited a shift toward fat oxidation in both groups, reflected by decreased RER and elevated FFAs (P < 0.001). Despite similar FFA concentrations, individuals with obesity demonstrated lower BHB concentrations (P < 0.001) following the fast when compared to their lean counterparts. Upon refeeding, individuals with obesity demonstrated lower 2-hour postprandial glucose excursions compared to lean participants (P < 0.001).

Conclusion: The presence of obesity may elicit a paradoxical advantage in restoring carbohydrate metabolism following short-term fasting. We speculate that fasting may alleviate basal hyperinsulinemia-induced insulin resistance, which partially counteracts fasting-induced glucose intolerance.

Trial registration: This trial was registered on ClinicalTrials.gov (NCT05886738).

Exogenous ketone supplementation can elevate heart rate (HR) but the effects on cardiac autonomic modulation remain unclear. HR variability was analyzed from 18 healthy adults (23±3 yr; n=10 females) ingesting 0.3 or 0.6 g/kg ketone monoester or placebo in a randomized crossover, double-blind design. Compared to placebo, both ketone doses increased plasma β-hydroxybutyrate and reduced the percentage of successive R-R intervals that differ by ≥50-ms (pRR50) and the root mean square of successive differences (RMSSD) at 45- (both p<0.02) and 120-min post-ingestion (both p<0.01). Acute ketone ingestion decreases HR variability measures associated with cardiac vagal modulation.

REDs negatively impacts bone mineral density (BMD), menstruation, growth, and maturation. The prevalence of REDs indicators in artistic adolescent athletes is unknown. The primary objective of this study was to examine the prevalence and factors associated with REDs in female adolescent artistic athletes. The secondary objective was to assess BMD and associated factors. 20 artistic swimmers, 20 recreational/competitive dancers, 20 vocational dancers, and 14 figure skaters, 9-19 years old (mean 15.3±2.6), participated in this cross-sectional study. Participants completed demographic/medical/menstrual history questionnaires, and the Eating Disorder Examination Questionnaire. Dual X-ray absorptiometry (DXA) was completed at the total body less head (TBLH), 33% distal radius, lumbar spine, and femoral neck. Firth's penalized logistic regression examined odds of REDs risk (demonstrated ≥1 indicator, yes/no), and multivariable modelling examined aBMD differences between cohorts. 34/74 athletes (45.9%) demonstrated ≥1 primary REDs indicator. Age, height, lean body mass, weekly training hours, sport specialization status, injury history, or sport were not associated with REDs risk. Relative to artistic swimmers, REDs risk odds ratios were 0.33 (95%CI:0.08-1.46) for recreational/competitive dancers, 1.15 (95%CI:0.33-4.05) for vocational dancers, and 0.73 (95%CI:0.15-3.44) for figure skaters. Relative to artistic swimmers, marginal-mean aBMD was greater by 0.066g/cm2 (95%CI:0.026-0.105) in recreational/completive dancers, 0.070g/cm2 (95%CI;0.026-0.113) in vocational dancers, and 0.081g/cm2 (95%CI:0.035-0.127) in figure skaters relative to artistic swimmers. Marginal-mean femoral neck aBMD was 0.104g/cm2 (95%CI:0.022-0.186) greater in recreational/competitive dancers and 0.118g/cm2 (95%CI:0.035-0.178) greater in vocational dancers compared to artistic swimmers. High prevalence of REDs indicators emphasizes the need for REDs screening and prevention in artistic sports.

High-intensity interval training (HIIT) is an effective strategy for enhancing exercise performance by stimulating skeletal muscle mitochondria and increasing their oxidative metabolic capacity. HIIT is also known to stimulate the mechanistic target of rapamycin complex 1 (mTORC1), a key regulatory factor in muscle protein anabolism; however, the role of mTORC1 in HIIT-induced mitochondrial adaptations remains unclear. We hypothesized that mTORC1 modulates mitochondrial adaptation induced by exercise training and investigated the effects of in vivo administration of rapamycin, a canonical inhibitor of mTOR, on skeletal muscle mitochondria after chronic HIIT. Male C57BL6/J mice (n = 21) were evenly assigned to three groups: one group served as the sedentary control (SED), another group performed 4 weeks of HIIT through loaded swimming five times per week (HIIT), and the third group underwent HIIT received intraperitoneal rapamycin administration (HIIT+RAPA). Twenty-four hours after completing the final training session, the animals were anesthetized and euthanized, following which the gastrocnemius, plantaris, and soleus muscles were collected, and their mitochondrial enzyme activities, content, morphology, and regulatory protein levels were evaluated. The combination of HIIT and rapamycin administration increased mitochondrial oxidative phosphorylation (OXPHOS) subunits (P = 0.0363 vs. HIIT, plantaris; P = 0.0176 vs. HIIT, soleus) and decreased the levels of proteins involved in mitochondrial fusion/fission (P = 0.0170 vs. HIIT, gastrocnemius OPA1; P = 0.0140 vs. HIIT, gastrocnemius DRP1 Ser616). Additionally, the number and circularity of mitochondria were increased only in the soleus muscle in the HIIT+RAPA group. These findings indicate that the regulatory role of rapamycin-sensitive mTORC1 on the mitochondrial molecular response and morphological changes in skeletal muscle induced by swimming-type HIIT varies across different skeletal muscles.

The 2026 FIFA World Cup will be held in 16 cities across the United States, Mexico, and Canada, exposing tens of thousands of workers to varying occupational heat stress in June-July. While prior research largely examined risks to players and spectators, this study evaluates heat exposure among the workforce. Using 30 years (1991-2020) of hourly meteorological data, we calculated wet-bulb globe temperatures (WBGT) and assessed exceedance of NIOSH Recommended Exposure Limits (REL) and Recommended Alert Limits (RAL) across multiple activity levels and work/rest schedules. Results show inter-city variation. Hot, humid locations such as Houston, Miami, and Monterrey often reach maximum WBGTs near 31°C, frequently exceeding safety thresholds, particularly for higher workloads and longer shifts. Cooler cities like Seattle and San Francisco usually have maximum WBGTs below 20°C and remain under thresholds in typical conditions but face acute hazards during extreme events, such as the 2021 Pacific Northwest heat wave when WBGTs exceeded 32°C. Shading reduces heat stress by lowering peak WBGTs by ~2-3°C and substantially decreasing RAL and REL exceedance frequencies. Acclimatization further influences risk, as lower RAL thresholds for unacclimatized workers result in more frequent and prolonged exceedances across all work intensities and rest schedules compared with acclimatized workers. These findings highlight the need for venue-specific heat management plans reflecting local climate, workload, and rest patterns. Given varied protections, FIFA and host cities should adopt evidence-based measures such as flexible scheduling, hydration and cooling access, and acclimatization protocols, along with contingency plans for rare extreme heat waves.

Sex and gender inequities in biomedical research are well-documented. To evaluate the recent exercise physiology literature, we analyzed participants, authors, and adherence to Sex and Gender Equity in Research (SAGER) guidelines in 629 systematically-selected original research articles (2018-2020) across six peer-reviewed journals. Nearly half of studies (46%) included only male/men (M/M) participants, 44% were mixed, and 8% were female/women (F/W)-only. Only 27% of authors were women, with even lower representation among senior authors (16%) and those with >2 publications (12%). Articles with women senior authors had 72% more women co-authors, and there was a dose-dependent association between women authors and inclusion of F/W participants. Articles adhered to 29 (20-43)% of relevant SAGER guidelines. Over half (58%) used inaccurate or unclear sex/gender-related language, and only 10-34% followed guidelines that support discovery of sex/gender-related differences. F/W-only articles were more likely than M/M-only to report (79% vs 12%), justify (69% vs 5%), and discuss (62% vs 20%) their single-sex/gender status. Articles with women authors were more likely to communicate clearly about sex/gender but otherwise had similarly poor adherence to SAGER guidelines. There are likely complex reasons why male bodies and men's voices continue to be centered in exercise physiology research. Our data implicate several logistical, attitudinal, and cultural contributors that warrant investigation and intervention. Structural support and enforcement will be needed to increase F/W inclusion and align research and reporting practices with SAGER guidelines. Associations between women authors and equitable practices suggest compound benefits of investing in recruitment and retention of women researchers.

Previous studies have shown that supraspinal excitability is higher during arm cycling than a position- and intensity-matched tonic contraction, but the underlying mechanisms remain unclear. This study aimed to determine whether long-interval intracortical inhibition (LICI) occurs during arm cycling and if LICI differs between arm cycling and tonic contraction. A paired-pulse transcranial magnetic stimulation (TMS) protocol assessed LICI using a supramaximal conditioning pulse that produced a silent period of approximately 150 ms, followed by a test pulse with a 100 ms interstimulus interval. Stimulation occurred at the 4 o'clock position to align the test pulse with the ascending limb of the biceps brachii EMG profile during the elbow flexion phase. Additionally, a single-pulse TMS stimulation was delivered 100 ms after the 4 o'clock position. Motor-evoked potentials (MEPs) were measured as ratios: a position-matched ratio of test pulse-evoked MEP over single pulse-evoked MEP. MEP ratios were analyzed for peak-to-peak amplitude during arm cycling and tonic contraction. Results showed that LICI was present during arm cycling (t(13) = 3.5, p < 0.001, 95% CI [-3.2, -0.75], but no significant difference in LICI was found between arm cycling and tonic contraction (t(13) = 1.3, p = 0.242, 95% CI [-0.23, -0.06]). These findings suggest that while LICI is present during arm cycling, it is not task-dependent.

To increase exercise adherence, there is a growing shift toward telehealth exercise-based programs. Alongside, passive heat therapy is gaining attention as an alternative approach to induce physiological adaptations, especially for individuals unable to exercise. However, heat therapy may reduce perceived effort, complicating actual assessment of physiological strain in telehealth settings. We assessed the relationship and agreement between physiological and perceptual strain in twelve older men (median age: 68 years) during intermittent exercise (three, 30-minute cycling bouts at increasing rates of metabolic heat production of 150, 200, and 250 W·m-2, each separated by 15 minutes of rest) in the heat (40°C) before and after 7 consecutive days of warm-water immersion (~40°C), with core (rectal) temperature clamped at ~38.5°C for 60 minutes. Physiological strain (PSI) was indexed from core temperature and heart rate and adjusted for skin temperature (aPSI) while perceptual strain (PeSI) used rating of perceived exertion and thermal sensation. Linear mixed models assessed the relationship, and Bland-Altman analysis quantified the agreement between measures (mean bias (95% [LoA]). PSI and aPSI increased with perceptual strain (P<0.001) and were not influenced following acclimation (P>0.610). Similarly, the agreement between physiological and perceptual strain was not affected by passive heating (PSI: -0.4 AU; aPSI: -0.8 AU), but the 95% LoA were wide (PSI: [-4.1 to 3.0 AU]; aPSI: [-4.5 to 2.9 AU]). Although physiological and perceptual strain are linearly related, individual variability may limit the utility of perceptual indices as surrogate markers of physiological strain in older adults during exercise. ClinicalTrials.gov identifier: NCT05838612.

Several randomized clinical trials have been undertaken to evaluate the effect of vitamin D supplementation on reducing the risk of cardiovascular disease (CVD) or CVD mortality; however, mixed results have been reported. The objective of this analysis is to quantify the effect of vitamin D supplements on CVD events and CVD mortality in adults. PubMed, the Cochrane Library and ClinicalTrial.gov were searched for randomized placebo-control trials on adults using common keywords related to vitamin D and CVDs. Two reviewers independently extracted data. The risk of bias was assessed using the Cochrane tool. Data analysis was done using Comprehensive Meta-Analysis V2 (Biostat, Englewood, NJ, USA) to calculate risk ratio (RR) and 95% confidence interval (95%CI). The systematic review and meta-analysis have been registered at PROSPERO (CRD42020165293). One thousand two hundred twenty four abstracts were retrieved, of which 9 (compromising 114 379 participants) were used. This analysis reveals that compared with placebo, vitamin D did not reduce any CVD events (RR = 0.95, 95%CI: 0.88-1.04), CVD mortality (RR = 1.04, 95%CI: 0.871-1.242), myocardial infarction event (RR = 0.96, 95%CI: 0.83-1.11), or myocardial infarction mortality (RR = 1.527, 95%CI: 0.828-2.816). Current evidence does not support the use of vitamin D for the prevention of major cardiovascular events. PROSPERO Registration Number: (CRD42020165293).