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

Changes in hydration status occur throughout the day affecting physiological and behavioural functions. However, little is known about the hydration status of free-living Japanese children and the seasonality of this response. We evaluated hydration status estimated by urine osmolality (Uosm) in 349 children (189 boys and 160 girls, 9.5 ± 2.6 years, range: 6-15 years) upon waking at home and during a single school day in spring (April) and summer (July). Further, we assessed the efficacy of employing self-assessment of urine colour (UC; based on an 8-point scale) by children to monitor their hydration status. Early morning Uosm was greater in the spring (903 ± 220 mOsm L^-1; n = 326) as compared to summer (800 ± 244 mOsm L^-1; n = 125) (P = 0.003, paired t test, n = 104). No differences, however, were observed in Uosm during the school day (P = 0.417, paired t test, n = 32). While 66% and 50% of children were considered underhydrated (Uosm ≥ 800 mOsm L^-1) upon waking in the spring and summer periods, respectively, more children were underhydrated (∼12%) during the school day. Self-reported UC was similar between seasons as assessed in the morning and school day (P ≥ 0.101, paired t test), which differed from the pattern of responses observed with Uosm. We showed that a significant number of Japanese children are likely underhydrated especially in the spring period. Children do not detect seasonal changes in hydration from self-assessed UC, limiting its utility to manage hydration status in children.

The effects of exogenous ketones on appetite and food intake remain elusive, especially for people with type 2 diabetes (T2D). This study aimed to determine whether acute ingestion of an oral ketone monoester supplement (KME) affected appetite sensations, prospective food consumption and intake in T2D. Results showed that acute KME ingestion did not significantly alter appetite scores. However, there was a tendency for lower energy intake during an ad libitum meal 3 h following ketone ingestion compared to non-energetic placebo. Further research is warranted to understand the long-term effects of exogenous ketones for energy and macronutrient intake in T2D.

The purpose of this study was to quantify the total energy expenditure (TEE) of international female rugby union players. Fifteen players were assessed over 14 days throughout an international multi-game tournament, which represented two consecutive one-match microcycles. Resting metabolic rate (RMR) and TEE were assessed by indirect calorimetry and doubly labelled water, respectively. Physical activity level (PAL) was estimated (TEE:RMR). Mean RMR, TEE, and PAL were 6.60 ± 0.93 MJ·day^-1 (1578 ± 223 kcal·day^-1), 13.51 ± 2.28 MJ·day^-1 (3229 ± 545 kcal·day^-1), and 2.0 ± 0.3 AU, respectively. There was no difference in TEE (13.74 ± 2.31 (3284 ± 554 kcal·day^-1) vs. 13.92 ± 2.10 MJ·day^-1 (3327 ± 502 kcal·day^-1); p = 0.754), or PAL (2.06 ± 0.26 AU vs. 2.09 ± 0.23 AU; p = 0.735) across microcycles, despite substantial decreases in training load (total distance: -8088 m, collisions: -20 n, training duration: -252 min). After correcting for body composition, there was no difference in TEE (13.80 ± 1.74 (3298 ± 416 adj. kcal·day^-1) vs. 13.16 ± 1.97 (3145 ± 471 adj. kcal·day^-1) adj. MJ·day^-1, p = 0.190), RMR (6.49 ± 0.81 (1551 ± 194 adj. kcal·day^-1) vs. 6.73 ± 0.83 (1609 ± 198 adj. kcal·day^-1) adj. MJ·day^-1, p = 0.633) or PAL (2.15 ± 0.14 vs. 1.87 ± 0.26 AU, p = 0.090) between forwards and backs. For an injured participant (n = 1), TEE reduced by 1.7 MJ·day^-1 (-401 kcal·day^-1) from pre-injury. For participants with illness (n = 3), TEE was similar to pre-illness (+0.49 MJ·day^-1 (+117 kcal·day^-1)). The energy requirements of international female rugby players were consistent across one-match microcycles. Forwards and backs had similar adjusted energy requirements. These findings are critical to inform the dietary guidance provided to female rugby players.

Eating in the absence of hunger (EAH) has been associated with overweight and obesity during childhood. The gold standard to assess this behavior is a laboratory-based protocol, but a questionnaire to assess EAH more efficiently in children and adolescents has been developed and validated in English. We assessed construct validity (structural and convergent validity) and reliability (internal consistency and temporal stability) of a French translation of the EAH Questionnaire for Children and Adolescents among French-Canadian youths. We recruited participants in Montreal (Canada) aged 7-15 years old, who completed the questionnaire and provided anthropometric data. We asked participants to complete the questionnaire a second time ∼4 weeks later. The questionnaire consists of 14 questions and 3 subscales that assess EAH due to negative affect, fatigue/boredom, and external cues. We performed an exploratory factor analysis to test the factor structure and we calculated Cronbach alpha coefficients and intra-class correlations to assess internal consistency and temporal stability, respectively. We assessed associations between EAH and BMI z-score using Pearson correlations. We included 196 participants (50% girls; mean (SD) 11.9 (2.3) years old) for the first completion and 153 for the second completion. The exploratory factor analysis generated the same three subscales as the original questionnaire: negative affect (α = 0.86; ICC = 0.78), fatigue/boredom (α = 0.75; ICC = 0.70), and external cues (α = 0.68; ICC = 0.54). Participant's BMI z-scores were positively associated with the average scores from the negative affect subscale (r = 0.19; ρ = 0.009). Our results suggest that this questionnaire has an adequate construct validity, internal consistency, and temporal stability.

Canada's food guide (CFG) 2019 provides dietary guidance for all Canadians; however, there is no tool available to help Canadians easily determine how individual foods align with CFG. Therefore, the objectives of this study were (1) to develop a nutrient profile model, Canadian Food Scoring System (CFSS), to rank the healthfulness of individual foods according to the recommendations of CFG; and (2) to assess its validity. The CFSS was developed based on CFG, leveraging existing Canadian labelling regulations to set quantitative criteria for the CFG recommendations. The CFSS included three main steps: (1) classifying foods into the nutritious food categories and assigning points based on the alignment with the recommendations of CFG; (2) deducting points based on the levels of saturated fat, sugars, and sodium using thresholds from Canadian front-of-pack labelling regulations; and (3) calculating the final score from the first two steps to classify foods into one of five categories: "very poor," "poor," "fair," "good," or "excellent" choice. Convergent validity was assessed by examining the alignment of the CFSS with Health Canada's CFG-Food Classification System using a national food composition database and the Healthy Eating Food Index-2019 using nationally representative dietary intake survey data. The CFSS showed strong correlation with the CFG-Food Classification System (ρ = 0.782, p < 0.001) and moderate correlation with the Healthy Eating Food Index-2019 (r = 0.636, p < 0.001), indicating good convergent validity both at the food and dietary level. The newly developed CFSS can assess the alignment of individual foods with CFG, which can be used to help Canadians more easily make healthy food choices.

Mitochondrial dysfunction is implicated in heat-induced skeletal muscle (SKM) injury and its underlying mechanisms remain unclear. Evidence suggests that cellular ions and molecules, including divalent cations and adenine nucleotides, are involved in the regulation of mitochondrial function. In this study, we examined Ca²⁺, Mg²⁺, and NAD⁺ levels in mouse C2C12 myoblasts and SKM in response to heat exposure. During heat exposure, mitochondrial Ca²⁺ levels increased significantly, whereas cytosolic Ca²⁺ levels remained unaltered. The mitochondrial Ca²⁺ levels in the SKM of heat-exposed mice were 28% higher compared to control mice. No changes in cytosolic Ca²⁺ were detected between the two groups. Following heat exposure, cytosolic and mitochondrial Mg²⁺ levels were reduced by 47% and 23% in C2C12 myoblasts, and by 51% and 44% in mouse SKMs, respectively. In addition, heat exposure decreased mitochondrial NAD⁺ levels by 32% and 26% in C2C12 myoblasts and mouse SKMs, respectively. Treatment with the NAD⁺ precursor nicotinamide riboside (NR) partially prevented heat-induced depletion of NAD⁺. Additionally, NR significantly reduced heat-increased mitochondrial fission, mitochondrial depolarization, and apoptosis in C2C12 myoblasts and mouse SKMs. No effects of NR on heat-induced changes in intracellular Ca²⁺ and Mg²⁺ levels were observed. This study provides in vitro and in vivo evidence that acute heat stress causes alterations in mitochondrial Ca²⁺, Mg²⁺, and NAD⁺ homeostasis. Our results suggest mitochondrial NAD⁺ homeostasis as a therapeutic target for the prevention of heat-induced SKM injury.

This study investigated skeletal muscle tissue oxygenation (StO₂) desaturation in males and females across the adult lifespan. One hundred-two individuals (51 females) of 41 young, 34 midlife, and 27 older adults completed a vascular occlusion test with near-infrared spectroscopy (NIRS + VOT). This included five minutes of arterial occlusion, inducing transient ischemia in the forearm flexor muscle group while recording StO_2. The magnitude of desaturation (StO_2mag) was quantified as the difference between baseline StO₂ and the minimum StO₂ value observed during ischemia. The rate of desaturation was also examined. Forearm adipose tissue thickness (ATT), forearm lean mass, and handgrip muscular strength were measured. A p ≤ 0.05 was considered significant. Two-way between factor Analysis of variance (ANOVAs) indicated that males exhibited significantly (p < 0.001) less ATT than females (collapsed across age) and that forearm lean mass (p < 0.001) and muscular strength (p < 0.001) decreased across the lifespan independent of sex. Bivariate analyses revealed significant (p < 0.05) associations for sex, age, ATT, forearm lean mass, and muscular strength with the desaturation metrics. The ATT values demonstrated the strongest relations with StO_2mag and desaturation rate (r = -0.620 and 0.618). Using a model comparison approach, ATT plus age offered the best predictive power for StO_2mag and desaturation rate (R² = 0.456 and 0.438) such that the inclusion of sex did not improve the models. These findings suggested differences in desaturation were primarily explained by variations in ATT and, to a lesser extent, age, but biological sex had no meaningful effect. Future studies must determine what other factors influence desaturation during ischemia.

Associations between daily time spent in physical activity (PA), sedentary behaviour (SB) and sleep (collectively referred to as 'movement behaviour') and quality of life (QOL) are typically studied without considering they are compositional, co-dependant variables. Study objectives were to use compositional data analysis to: 1) examine the relationship between movement behaviour composition and QOL, 2) estimate the degree to which changing time spent in any movement behaviour within the movement behaviour composition is associated with QOL. 7,918 older Canadian adults ≥ 65 years of age from the Canadian Longitudinal Study on Aging were studied using a quasi-longitudinal study design. Daily time spent in PA and SB were derived from self-reported Physical Activity Scale for the Elderly responses. Nighttime sleep was self-reported separately. QOL was assessed through the Satisfaction with Life Scale. Movement behaviour composition was significantly associated with QOL. Relative time spent in SB was negatively associated with QOL [HR = 0.89 (95% CI: 0.86, 0.93)]. Relative time spent in sleep was positively associated with QOL [HR = 1.10 (95% CI: 1.05, 1.16)]. Time displacement estimates revealed that greatest change in QOL occurred when time spent in PA was decreased and replaced with SB [HR = 0.96 (95% CI: 0.92, 0.99) for 45 min/day displacement]. Using compositional data analysis is advantageous because it shows how reduction in SB and increase in PA and sleep can lead to improvements in QOL for older Canadian adults.

This study investigated the impact of menstrual cycle (MC) phases and resistance training (RT) on muscle cross-sectional area (CSA) in two MCs utilizing a within-subject design. Twenty women with regular MCs had their legs randomly allocated to either the control (CON) or RT condition, which included 16 training sessions over two MCs. CSA, estradiol (E2), and progesterone (P4) were assessed during the menstruation (M), ovulation (O), and luteal (L) phases in the first (M1, O1, L1) and second (M2, O2, L2) MCs and at the beginning of the third MC (M3). P4 values were significantly higher during the luteal phase than during menstruation (P < 0.0001) and ovulation (P < 0.0001). No significant differences in E2 concentrations were observed between the MC phases (P = 0.08). For the RT condition, the CSA showed significant increases at O2, L2, and M3 compared to baseline (M1) (all P < 0.0001). No significant changes were observed for the CON condition during the two MCs (P > 0.05). However, RT condition showed a significant change in average CSA across two MCs. Additionally, individual analyses revealed that 19 participants showed variation in CSA above or below the minimum detectable difference during the two MCs. These findings suggest that changes in muscle CSA observed during two MCs may not be exclusively attributed to RT.

Fatigability varies depending on sex and contraction intensity during sustained exercise. This study examined the responses of time to task failure (TTF), performance fatigability (PF), and muscle oxygenation (SmO₂) in males and females during isometric handgrip holds to failure (HTF) at 30% and 60% maximum voluntary isometric contraction (MVIC). Males (n = 12) and females (n = 12) performed a pre-MVIC, handgrip HTF at randomly ordered percentages of MVIC (either 30% or 60%), followed by a post-MVIC on the dominant arm. During the HTF testing, the TTF and SmO₂ responses were recorded, and PF was determined from the pre- to post-MVICs. TTF for 30% MVIC HTF was greater than 60% MVIC HTF (p < 0.001), but was not different between males and females (p = 0.117). PF exhibited an inverse relationship with intensity for each sex, while males demonstrated greater PF than females for both 30% and 60% MVIC HTF. For the 60% MVIC HTF, males demonstrated greater desaturation than females (CI_95% = [-28.1, -2.6%], p = 0.021, d = 0.621), but not for the 30% MVIC HTF (CI_95% = [-12.2, 7.9%], p = 0.315, d = 0.621). Sex differences in PF and SmO₂ may be attributed to the differences in muscle mass, absolute strength, contractile properties, and muscle metabolism between males and females. However, these proposed differences between males and females may not fully inform exercise performance (e.g., TTF). Sex-specific fatigue responses may be affected by complex physio-psychological mechanisms, and therefore, additional investigations under diverse exercise conditions are required to better prescribe exercise for both males and females.