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

Wildland firefighters can work at high intensity in hot environments for extended periods of time. The resulting heat strain may be modified by the environmental conditions (i.e., ambient temperature and humidity [RH]) even at equal wet-bulb globe temperatures. This investigation assessed if a hot and dry condition would create greater strain than moderate and high humidity at equivalent wet-bulb globe temperature (28°C). Twelve participants (age 24±2 y) walked at 40-50% maximum aerobic capacity for 90 and 40 min separated by a 20 min rest in dry (40°C, 20% RH), moderate-humidity (34°C, 50% RH), and high-humidity (29°C, 90% RH) conditions wearing fire resistant jacket, pants, gloves, and helmet with the neck and face exposed. Peak core temperature was higher in moderate-humidity (38.9±0.2°C, p=0.01) and high-humidity (38.9±0.6°C, p<0.01) than dry condition (38.5±0.3°C). Average net heat gain was less in dry (33±22 W) compared to moderate-humidity (38±23 W, p<0.01) and high-humidity (39±28 W, p<0.01). Peak heart rate (174±14 bpm, p=0.94), Physiological Strain Index (7.7±1.4 score, p=0.99), perceived exertion (8±2 rating, p=0.97), and Perceptual Strain Index (7.3±1.6 score, p=0.99) were not different in high-humidity compared to the dry condition (167±19 bpm, 6.9±1.3 score, 6±2 rating, 7.3±1.7 score, respectively). Whole-body sweat rate (15±6 mL/min, p=0.58) and thermal sensation (7±1 rating, p=0.37) were not different. Hiking in a humid condition while wearing protective garments creates greater exertional heat strain compared to a dry condition of equivalent wet-bulb globe temperature. Wildland firefighters should consider extra strategies to mitigate hyperthermia when humidity is high.

Royal Canadian Mounted Police (RCMP) cadets experience high volumes of potentially psychologically traumatic events, suggesting a need of normal cardiac cycle interval data on the cadets for comparison. We characterize the cardiac cycle of incoming RCMP cadets starting the 26-week training program. The cadets collected their cardiac data using the LLA Recordis™ device. Male RCMP cadets had higher (p<0.05) myocardial and diastolic performance indices, aortic valve open to aortic twist time, and isovolumic relaxation time than female RCMP cadets. Monitoring the cardiac cycle intervals in RCMP cadets can provide insights to changes in their heart function from their occupational demands.

Musculoskeletal injury (MSKi), depression, anxiety and burnout place a considerable burden on emergency services personnel and healthcare providers (HCP). Physical fitness is related to both mental and physical health in these populations but females in these are hugely underrepresented in this literature. As female representation in first-responder and HCP roles increases, the need for female specific research is needed. This study examines physical fitness as a short-term indicator of future reproductive health, MSKi, and mental health for females employed as first-responders or HCP. Thirteen first-responders and 29 HCP completed an initial health and demographics questionnaire, a comprehensive physical assessment (e.g., bone mineral density, muscular strength, muscular endurance, muscular power, flexibility, and aerobic capacity), and a health questionnaire 6-7 months after the physical testing. We found that i) bone mineral density, relative upper body strength, and lowerbody power were related to sustaining future MSKi, ii) better lower body endurance and flexibility was related to future menstrual cycle disruptions, and iii) low bone mineral density was related future self-reported burnout and Patient Health Questionnaire score >10. Physical fitness characteristics can be helpful indicators of future MSKi risk, menstrual cycle disruptions, and mental health status in females employed in arduous occupations.

The first aim was to explore the difference in metabolic flexibility between sexes in response to changing exercise intensity under control conditions. The second aim was to evaluate metabolic flexibility between sexes in response to exercise intensity adding two different metabolically challenging stimuli (glycogen depletion and heat). Eleven males (22±3yrs, 176.2±4cm, 68.4±4.9kg and 60.2±4.1ml/kgFFM/min) and nine females (22±2yrs, 166.7±4.5cm, 61.9±2.9kg, 64.2±5.6 ml/kgFFM/min) performed a maximal incremental exercise test (30W every 3min) on a cycle ergometer under three conditions: control (24h high-carbohydrate diet followed by the incremental test), glycogen depletion (glycogen-depletion protocol followed by 24h low-carbohydrate diet and then the incremental test) and heat (24h high-carbohydrate diet followed by 30 min passive heating and then the incremental test in heat). In the last minute of each step, lactate was analysed, fat (FATox/FFM) and carbohydrate oxidation (CHox/FFM) and energy expenditure (EE/FFM) normalized to fat free mass was estimated by indirect calorimetry. Females presented a greater FATox/FFM as exercise intensity increases across conditions (control, glycogen depletion and heat) (p=0.006). In contrast, CHox/FFM was not significantly different between sexes at any specific intensity across conditions (p>0.05). Consequently, EE/FFM was higher in females throughout the different intensities across conditions (p=0.002). Finally, lactate concentration was not different between sexes at the same intensities across conditions (p=0.87). In conclusion, females present a greater metabolic flexibility, due to the higher FATox/FFM throughout the different intensities, regardless of whether the test is performed in a conditions emphasizing the oxidative pathway (glycogen depletion) or the glycolytic pathway (heat). Clinical trials:NCT05703100.

This study investigated the acute effects of ketone monoester on metabolic and neurocognitive indicators and underlying metabolism-brain-cognition interactions among young adults of healthy weight (HW) and those with overweight/obesity (OW). Forty participants were divided into two groups: HW (n = 20, age 23.80±3.96 years, body mass index [BMI] 21.49±1.80 kg/m²) and OW (n = 20, age 22.00±2.13 years, BMI 28.23±3.48 kg/m²). Each participant completed two trials (ketone monoester vs. placebo, 395 mg/kg dose) in a randomized order. Metabolic indicators (blood beta-hydroxybutyrate [BHB] and glucose) and neurocognitive function (causal density via functional near-infrared spectroscopy and cognitive interference via the Stroop task) were measured at baseline, 30 minutes, and 90 minutes post-supplementation. A chain mediation model was constructed to test the indirect effects of BHB level on cognitive interference through mediators like blood glucose and causal density. In the linear mixed models, significant effects were observed for trial (β = -0.92, 0.20, -0.04, 25.53) and assessment time (β = 0.50, -0.14, 0.09, -62.88) in BHB, glucose, causal density, and cognitive interference (p < 0.05), but not for group factors. Compared to OW, the effects of ketone monoester on prefrontal connectomes were more enduring in the HW (p < 0.05). Elevated BHB level improved cognitive function through decreasing glucose level and increasing causal density, with estimate of -0.63. Acute ketone monoester supplementation elevated levels of blood BHB and prefrontal connectomes and decreased levels of glucose and cognitive interference, regardless of weight status. Elevated blood BHB enhanced cognitive function through multi-tiered neurometabolic pathways.

Occupational heat stress increases acute kidney injury risk. Drinking a soft drink sweetened with high fructose corn syrup further elevates this acute kidney injury risk. However, the impact of sucrose, another fructose containing-sweetener, on acute kidney injury risk remains unexplored. We tested the hypothesis that drinking a sucrose-containing sports drink increases acute kidney injury risk when compared to drinking a sugar-free sports drink during four hours of simulated occupational heat stress. Ten healthy adults consumed a sucrose-containing or sugar-free sport drink ad libitum during four-hour exposures to wet bulb globe temperatures of ~28°C. 30 min of work and 30 min of rest were completed each hour. Work involved treadmill walking at a fixed rate of metabolic heat production (sucrose-containing: 6.0±1.2 W/kg, sugar-free: 5.5±0.9 W/kg, p=0.267). The product of urinary insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase-2, normalized to urine specific gravity ([IGFBP7·TIMP-2]USG), provided an acute kidney injury risk index. Mean core (intestinal: n=13, rectal: n=7) temperature (sucrose-containing: 37.5±0.1°C, sugar-free: 37.5±0.3 °C; p=0.914), peak core temperature (sucrose-containing: 37.8±0.2°C, sugar-free: 37.9±0.3 °C; p=0.398), and percent changes in body mass (sucrose-containing: -0.5±0.4%, sugar-free: -0.3±0.6%; p=0.386) did not differ between groups. [IGFBP7∙TIMP-2]USG increased in both groups (time effect: p=0.0254) with no drink (p=0.675) or interaction (p=0.715) effects. Peak change [IGFBP7∙TIMP-2]USG did not differ between sucrose-containing (median 0.0116 [-0.0012, 0.1760] (ng/mL)²/1000) and sugar-free (median 0.0021 [0.0003, 0.2077] (ng/mL)²/1000; p=0.796). Sucrose-containing sports drink consumption during simulated occupational heat stress does not modify acute kidney injury risk when compared to sugar free-sport drink consumption.

Until recently, most dietary guidelines and related food policies in Canada focused on total sugars, but recent evidence suggests that free sugars are of greater public health concern. Starting in 2017, our research group received federal funding to fill critical gaps related to free sugars and health. In this commentary, we describe our work related to tracking free sugars in the Canadian food supply and simulating the diet and health impacts of product reformulation. We then summarize how our work has influenced policymaking in Canada with examples of our knowledge translation efforts, and provide a future research and policy agenda based on our findings. Overall, there is significant room for Canadian food policies to target free sugars reductions in food and diets to address overconsumption of this nutrient of public health concern.

Understanding the dietary patterns of First Nations is crucial for addressing health disparities and promoting well-being. Historical assaults (colonization and loss of control over their lands) have strongly altered dietary practices and impacted health outcomes for generations. Canada conducts regular surveys to assess the extent to which individuals adhere to dietary guidelines. However, Indigenous peoples living on reserves are excluded from these surveys. This study aims to assess the diet quality of First Nations adults using the Healthy Eating Food Index-2019 (HEFI-2019) and the Canadian Healthy Eating Index 2007 (C-HEI 2007) and identify their influencing factors. Data were collected from adults (19 years and older) across ninety-two First Nations communities throughout Canada. Participants provided information on sociodemographic factors and dietary intake using structured questionnaires and 24 h dietary recalls. Statistical analyses included mean scores and regression models to assess associations between dietary indices and influencing factors. The mean HEFI-2019 and C-HEI 2007 scores among First Nations adults were 35/80 and 49/100, respectively, indicating suboptimal adherence to dietary guidelines compared to the Canadian population. Factors such as region, age, sex, education level, number of working people in the household, smoking status, and traditional food intake significantly influenced diet quality. This study underscores the importance of understanding and improving the diet quality of First Nations adults as measured by HEFI-2019 and C-HEI 2007 scores. While acknowledging the low adherence to dietary guidelines, particularly in younger age groups, the study highlights the positive influence of traditional foods on diet quality within Indigenous communities.

Heat exposure's effect on glucose tolerance depends on the amount of body exposed, likely relating to autonomic nervous system balance. We assessed how partial-body heat exposure at two different levels of the lower extremities affects glucose tolerance and autonomic nervous system balance, measured via heart rate variability. We hypothesized feet-heating would improve glucose tolerance without affecting heart rate variability, while calf-heating would worsen glucose tolerance and decrease heart rate variability compared to a thermoneutral control condition. In a randomized, controlled, crossover trial, healthy participants' (N = 31, 23(3) years, 45% male) glucose tolerance was measured in (A) thermoneutral; (B) feet-heating; and (C) calf-heating conditions. Every 30 min for 2 h, blood glucose, heart rate, heart rate variability, tympanic temperature, thermal comfort scores, and blood pressure were measured. There were significant interactions between condition and time for blood glucose (F (4.6,72.6) = 2.6, p = 0.036), heart rate (F (3.4, 54.5) = 3.5, p = 0.017), heart rate variability (F (4.3,63.2) = 7.5, p < .0001), tympanic temperature (F (8, 268) = 2.4, p = 0.014), and thermal comfort scores (F (8, 248) = 22.1, p < 0.0001). Calf-heating increased 90 min glucose (+12 (95% confidence interval, CI: 3-21) mg/dL, p = 0.013) and decreased heart rate variability throughout (mean decrease: 13%-22%, p < 0.007), while feet-heating lowered 90 min glucose (-7 (95% CI: -16 to +1) mg/dL, p = 0.090) without affecting heart rate variability (p = 0.14-0.99). Blood pressure and body temperature were similar between conditions, but heart rate and thermal comfort scores increased with heating. Calf-heating worsens, while feet-heating may improve, glucose tolerance. Changes in heart rate variability coincided with changes in glucose tolerance despite unchanged body temperature. Whether heart rate variability can be used to monitor autonomic nervous system balance during heating to optimize its acute effect on glycemic indices should be further explored.

Explosive movements requiring high force and power outputs are integral to many sports, posing distinct challenges for the neuromuscular system. Traditional resistance training can improve muscle strength, power, endurance, and range of motion; however, evidence regarding its effects on athletic performance, such as sprint speed, agility, and jump height, remains conflicting. The specificity of resistance training movements, including velocity, contraction type, and joint angles affects performance outcomes, demonstrates advantages when matching training modalities with targeted sports activities. However, independent of movement speed, the intent to contract explosively (ballistic) has also demonstrated high velocity-specific training adaptations. The purpose of this narrative review was to assess the impact of explosive or ballistic contraction intent on velocity-specific training adaptations. Such movement intent may predominantly elicit motor efferent neural adaptations, including motor unit recruitment and rate coding enhancements. Plyometrics, which utilize rapid stretch-shortening cycle movements, may augment high-speed movement efficiency and muscle activation, possibly leading to improved motor control through adaptations like faster eccentric force absorption, reduced amortization periods, and quicker transitions to explosive concentric contractions. An optimal training paradigm for power and performance enhancement might involve a combination of maximal explosive intent training with heavier loads and plyometric exercises with lighter loads at high velocities. This narrative review synthesizes key literature to answer whether contraction intent or movement speed is more critical for athletic performance enhancement, ultimately advocating for an integrative approach to resistance training tailored for sports-specific explosive action.