Measurement of 24-h continuous human CH4 release in a whole room indirect calorimeter.

We describe the technology and validation of a new whole room indirect calorimeter (WRIC) methodology to quantify volume of methane (VCH4) released from the human body over 24 h concurrently with the assessment of energy expenditure and substrate utilization. The new system extends the assessment of energy metabolism by adding CH4, a downstream product of microbiome fermentation that could contribute to energy balance. Our new system consists of an established WRIC combined with the addition of off-axis integrated-cavity output spectroscopy (OA-ICOS) to measure CH4 concentration ([CH4]). Development, validation, and reliability of the system included environmental experiments to measure the stability of the atmospheric [CH4], infusing CH4 into the WRIC and human cross-validation studies comparing [CH4] quantified by OA-ICOS and mid-infrared dual-comb spectroscopy (MIR DCS).Our infusion data indicated that the system measured 24-h [CH4] and VCH4 with high sensitivity, reliability, and validity. Cross-validation studies showed good agreement between OA-ICOS and MIR DCS technologies (r = 0.979, P < 0.0001). Human data revealed 24-h VCH4 was highly variable between subjects and within/between days. Finally, our method to quantify VCH4 released by breath or colon suggested that over 50% of the CH4 was eliminated through the breath. The method allows, for the first time, measurement of 24-h VCH4 (in kcal) and therefore the measurement of the proportion of human energy intake fermented to CH4 by the gut microbiome and released via breath or from the intestine; also, it allows us to track the effects of dietary, probiotic, bacterial, and fecal microbiota transplantation on VCH4.NEW & NOTEWORTHY This is the first time that continuous assessment of CH4 is reported in parallel with measurements of O2 consumption and CO2 production inside a whole room indirect calorimeter in humans and over 24 h. We provide a detailed description of the whole system and its parts. We carried out studies of reliability and validity of the whole system and its parts. CH4 is released in humans during daily activities.

Is physical education an effective way to increase physical activity in children with lower cardiorespiratory fitness?

Several findings revealed the importance of accruing moderate and vigorous physical activity (MVPA) to improve health. Physical education (PE) may play an important role on promoting children's MVPA. However, it remains unknown whether PE might be effective when increasing physical activity (PA) levels in children with lower cardiorespiratory fitness (CRF). Therefore, the aim of this study was to assess children's PA during PE and during days with and without PE with a special focus on CRF status. One hundred and fifty Spanish children and adolescents from 3rd to 12th grade were recruited. PA levels were assessed with GT3X accelerometers. Peak oxygen uptake (VO2peak ) was estimated using a portable breath by breath Metamax 3B. Participants were classified as healthy aerobic fitness (HAF) and unhealthy aerobic fitness (UHAF) according to standardized cut-off point criteria. During PE, students with HAF accrued more MVPA than those with UHAF (8.7 vs 5.7 min/session; P ≤ 0.001). MVPA was higher on PE days than days without for both UHAF (50.0 vs 42.7 min/day; P ≤ 0.05) and HAF students (56.9 vs 49.4 min/day; P ≤ 0.05). Although less active during PE, students with lower CRF accumulated more MVPA and total PA on PE days than days without PE. An increase in PE days might be a smart policy to raise the recommended PA levels, regardless of CRF status.

Weekly training hours are associated with molecular and cellular body composition levels in adolescent athletes.

AIM: We aimed to explore associations between hours per week of sports training and molecular and cellular body composition components in adolescent athletes. METHODS: A total of 33 female athletes (13.3+/-3.5 years; 47.8+/-12.6 kg; 154+/-14.0 cm) and 90 male athletes (14.1+/-2.7 years; 60.6+/-17.8 kg; 167+/-16.2 cm) were measured. Based on the total of hours per week of training, athletes were divided into tertiles: <4.5 h/week; 4.5-8.9 h/week; 9 h/week. Dual-energy X-ray absorptiometry (DXA) was used to assess lean mass (lean), body fat (BF), percent body fat (%BF), bone mineral content (BMC) and density (BMD). Total body water (TBW), intracellular (ICW) and extracellular water (ECW) were assessed using bioelectrical impedance spectroscopy (BIS). Extracellular fluids (ECF), solids (ECS), body cell mass (BCM) and body fluid distribution (E/I) were calculated. Total hours per week of sports training (h/week), habitual physical activity (PA) and dietary were assessed by questionnaire. Statistics included analysis of covariance (ANCOVA) and simple regression analyses. RESULTS: Athletes training 9 h/week presented greater levels of TBW, lean, bone mass, BCM, and ECF and a lower %BF, independently of confounders. No significant differences in body composition estimates were found between athletes training <9 h/week. Hours per week of sports training were positively associated with fat free components, only in the group exercising 9 h/week CONCLUSIONS: In this group of Portuguese athletes from different sports we observed that training 9 h/week significantly improved body composition, especially fat free components, which may be important for a healthy growth and sports performance.

Body surface area estimation and its impact on predicting appendicular skeletal muscle mass with a mechanistic model based on the Reference Man.

The purpose of this study was to analyze the difference between the equations presented by Du Bois and Du Bois (1916) and Livingston and Lee (2001), used to estimate body surface area (BSA) and its impact on predicting appendicular skeletal muscle mass (ASMM) in adults, using a model based on the Reference Man (Fuller et al. 1992). Subjects were 666 Caucasian women (44.3+/-15.2 years, 63.7+/-10.5 kg, 1.57+/-0.07 m, 26.0+/-4.3 kg/m(2)) and 316 Caucasian men (42.8+/-15.4 years, 79.8+/-12.5 kg, 1.72+/-0.07 m, 26.8+/-3.8 kg/m(2)). Dual-energy X-ray absorptiometry was used to assess fat mass and fat-free mass. Du Bois's and Livingston's BSA equations were used to calculate ASMM according to Fuller's method. As compared to the new Livingston equation, Du Bois's equation underestimated ( p<0.05) BSA in women (-0.08 m(2)) and in men (-0.06 m(2)). On the other hand, ASMM was overestimated in the arms, legs, and total body with Du Bois's equation. This effect was of greater magnitude in obese subjects.