Inter-Day Reliability of Resting Metabolic Rate and Maximal Fat Oxidation during Exercise in Healthy Men Using the Ergostik Gas Analyzer

The attainment of high inter-day reliability is crucial to determine changes in resting metabolic rate (RMR), respiratory exchange ratio (RER), maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) after an intervention. This study aimed to analyze the inter-day reliability of RMR, RER, MFO and Fatmax in healthy adults using the Ergostik gas analyzer. Fourteen healthy men (age: 24.4 ± 5.0 years, maximum oxygen uptake (VO2max): 47.5 ± 11.9 mL/kg/min) participated in a repeated-measures study. The study consisted of two identical experimental trials (Day 1 and Day 2) in which the participants underwent an indirect calorimetry assessment at resting and during an incremental exercise test. Stoichiometric equations were used to calculate energy expenditure and substrate oxidation rates. There were no significant differences when comparing RMR (1999.3 ± 273.9 vs. 1955.7 ± 362.6 kcal/day, p = 0.389), RER (0.87 ± 0.05 vs. 0.89 ± 0.05, p = 0.143), MFO (0.32 ± 0.20 vs. 0.31 ± 0.20 g/min, p = 0.776) and Fatmax (45.0 ± 8.6 vs. 46.4 ± 8.4% VO2max, p = 0.435) values in Day 1 vs. Day 2. The inter-day coefficient of variation for RMR, RER, MFO and Fatmax were 4.85 ± 5.48%, 3.22 ± 3.14%, 7.78 ± 5.51%, and 6.51 ± 8.04%, respectively. In summary, the current results show a good inter-day reliability when RMR, RER, MFO and Fatmax are determined in healthy men using the Ergostik gas analyzer.

Withaferin A Promotes White Adipose Browning and Prevents Obesity Through Sympathetic Nerve-Activated Prdm16-FATP1 Axis

The increasing prevalence of obesity has resulted in demands for the development of new effective strategies for obesity treatment. The Withaferin A (WA) shows a great potential for prevention of obesity by sensitizing leptin signaling in the hypothalamus. However, the mechanism underlying the weight- and adiposity-reducing effects of WA remains to be elucidated. Here, we report that WA treatment induced white adipose tissue (WAT) browning, elevated energy expenditure (EE), decreased respiratory exchange ratio (RER), and prevented high-fat diet (HFD)-induced obesity. The sympathetic chemical denervation dampened the WAT browning and also impeded the reduction of adiposity in WA-treated mice. WA markedly up-regulated the levels of Prdm16 and FATP1 (Slc27a1) in the inguinal WAT (iWAT), and this was blocked by sympathetic denervation. Prdm16 or FATP1 knockdown in iWAT abrogated the WAT browning-inducing effects of WA, and restored the weight gain and adiposity in WA-treated mice. Together, these findings suggest that WA induces WAT browning through the sympathetic nerve-adipose axis; and the adipocytic Prdm16-FATP1 pathway mediates the promotive effects of WA on white adipose browning.

Withaferin A Promotes White Adipose Browning and Prevents Obesity Through Sympathetic Nerve-Activated Prdm16-FATP1 Axis

The increasing prevalence of obesity has resulted in demands for the development of new effective strategies for obesity treatment. The Withaferin A (WA) shows a great potential for prevention of obesity by sensitizing leptin signaling in the hypothalamus. However, the mechanism underlying the weight- and adiposity-reducing effects of WA remains to be elucidated. Here, we report that WA treatment induced white adipose tissue (WAT) browning, elevated energy expenditure (EE), decreased respiratory exchange ratio (RER), and prevented high-fat diet (HFD)-induced obesity. The sympathetic chemical denervation dampened the WAT browning and also impeded the reduction of adiposity in WA-treated mice. WA markedly up-regulated the levels of Prdm16 and FATP1 (Slc27a1) in the inguinal WAT (iWAT), and this was blocked by sympathetic denervation. Prdm16 or FATP1 knockdown in iWAT abrogated the WAT browning-inducing effects of WA, and restored the weight gain and adiposity in WA-treated mice. Together, these findings suggest that WA induces WAT browning through the sympathetic nerve-adipose axis; and the adipocytic Prdm16-FATP1 pathway mediates the promotive effects of WA on white adipose browning.

Niacin supplementation impairs exercise performance

Several pre-workout supplements contain niacin, although the exercise performance effects of niacin are poorly understood. The purpose of the present study was to examine the performance effects of niacin versus caffeine as a pre-workout supplement. Twenty-five untrained males were recruited to complete three identical ramped aerobic cycling exercise trials. Participants were administered caffeine (CA) at 5 mg/kg body weight, 1000 mg niacin (NI), or a methylcelluloce placebo (PL) supplement prior to each trial. NI treatment induced significantly higher respiratory exchange ratio (RER) during exercise compared to the CA treatment, but not the PL treatment (PL=0.87±0.08, NI=0.91±0.08, CA=0.87±0.08; p=0.02). Similarly, exercise time to exhaustion (in minutes) was significantly different between the NI treatment and the CA treatment, but not the PL treatment (PL=27.45±4.47, NI=26.30±4.91, CA=28.76±4.86; p<0.01). Habitual caffeine use (p=0.16), habitual aerobic exercise (p=0.60), and habitual resistance exercise (p=0.10) did not significantly affect RER. Similarly, habitual caffeine use (p=0.72), habitual aerobic exercise (p=0.08), and habitual resistance exercise (p=0.39) did not significantly affect total work performed. The elevated RER and decreased time to exhaustion in the NI treatment suggests limited lipid availability during exercise and impaired exercise performance.

Overshoot of the Respiratory Exchange Ratio during Recovery from Maximal Exercise Testing in Kidney Transplant Recipients

The overshoot of the respiratory exchange ratio (RER) during recovery from exercise has been found to be reduced in magnitude among patients with heart failure. The aim of this study is to investigate whether this phenomenon could also be present in patients with peripheral, and not cardiac, limitations to exercise such as kidney transplant recipients (KTRs). In this retrospective cross-sectional study, KTRs were evaluated with maximal cardiopulmonary exercise testing (CPET) assessing the RER overshoot parameters during recovery: the RER at peak exercise, the maximum RER value reached during recovery, the magnitude of the RER overshoot (RER mag = (RER max-peak RER)/peak RER%) and the linear slope of the RER increase after the end of exercise. A total of 57 KTRs were included in the study (16 females), all of them showing a significant RER overshoot (RER mag: 28.4 ± 12.7%). Moreover, the RER mag showed significant correlations with the fitness of patients (peak VO2: ρ = 0.57, p < 0.01) and cardiorespiratory efficiency (VE/VCO2 slope: r = −0.32, p < 0.05; oxygen uptake efficiency slope (OUES): r = 0.48, p < 0.01). Indeed, the RER mag was significantly different between the subgroups stratified by Weber’s fitness class or a ventilatory efficiency class. Our study is the first to investigate recovery of the RER in a population of KTRs, which correlates well with known prognostic CPET markers of cardiorespiratory fitness, determining the RER mag as the most meaningful RER overshoot parameter. Thus, the RER recovery might be included in CPET evaluations to further improve prognostic risk stratifications in KTRs and other chronic diseases.

Correlation of maximal respiratory exchange ratio with anaerobic power and maximal oxygen uptake in anaerobic trained athletes

Background and Study Aim. The respiratory exchange ratio (RER) is the ratio of the amount of carbon dioxide produced (VCO2) to the amount of oxygen uptake (VO2) is important. It indirectly informs about the predominant metabolic pathway to provide the energy needed during exercise. The relationship of maximal RER with aerobic and anaerobic capacity in athletes remains unclear. The purpose of this study was to investigate the relationship between maximal RER and anaerobic power and maximal oxygen uptake (VO2max) in anaerobic trained athletes. Material and Methods. Thirteen male alpine skiers (age 18.1 ± 3.1 years) competing in national and international competitions participated in the study. Athletes first performed an incremental treadmill run test to determine their VO2max (ml/kg/min), maximal RER (VCO2 / VO2) and maximal running speed (km/h). After 48 hours, the athletes performed the Wingate anaerobic test to determine peak power, mean power, minimum power, and fatigue index. Pearson correlation coefficients were used to examine the relations between variables. Results. Maximal RER was positively correlated with peak power (r = 0.587, p < 0.035), mean power (r = 0.656, p < 0.015) and minimum power (r = 0.674, p < 0.012). Maximal RER did not significantly correlate with fatigue index (p > 0.05). Maximal RER was negatively correlated with the VO2max (r = – 0.705, p < 0.007) and maximal running speed (r = – 0.687, p < 0.01). Conclusions. Maximal RER may be useful for evaluating anaerobic capacity in anaerobic-trained athletes. Measuring the maximal RER values of athletes during incremental exercise may provide information about physiological adaptations in response to physical training.

Comparison of Two Metabolic Simulators Used for Gas Exchange Verification in Cardiopulmonary Exercise Test Carts

IntroductionMetabolic simulators (MS) produce simulated human breaths for the purpose of verification of cardiopulmonary exercise test (CPET) equipment. MS should produce consistent identical breaths with known CO2 and O2 gas concentrations over a range of breath rates and tidal volumes. Reliability of a CPET metabolic cart depends on ongoing quality control and maintenance of the device, including intermittent verification with a MS. We compared two MS devices against two standard CPET systems.MethodsThe Vacumed 17056 (Vacumetrics, Ventura, CA) and Relitech (Relitech Systems BV, Nijkerk, The Netherlands) were used with two standard metabolic carts (Vyntus CPX and Vyntus ONE, both Vyaire Medical, Mettawa, IL, United States). Tidal volume (VT) was set at 2 and 3 L and breathing frequency ranged from 20 to 80 breaths per minute for each MS. At each set point, we measured three sets of 40 breaths. Primary outcome parameters collected were VT, oxygen consumption (v.O2), carbon dioxide production (v.CO2), and respiratory exchange ratio (RER).ResultsVT, RER, v.O2, and v.CO2 results as obtained from both MS were all within the limits of acceptability, at both tidal volume settings, and all ventilatory rates. No significant trends were identified for either MS device. The Relitech MS produced tidal volumes that were closer to the target VT for both CPET carts at both VT and all rates, but the results of both MS were within acceptable ranges.ConclusionVerification of CPET equipment using either the VM or RT metabolic simulator, producing highly accurate and predictable simulated breaths of known composition, enabling CPET laboratory managers to rely on subject test data obtained during cardiopulmonary exercise testing.

Relationship Between Physiological Fatigue and Muscular Fatigue Assessed Utilizing Surface Electromyography Wearable Technology

Introduction: The purpose of the study was to assess the relationship between upper leg muscle fatigue and physiological fatigue during a maximal exercise test. Methods: A total of 13, trained athletes participated and were tested for maximal oxygen uptake (VO2peak). Throughout the test, oxygen uptake respiratory exchange ratio (RER), and heart rate (HR) were recorded simultaneously with surface electromyography (sEMG) electrodes utilizing wearable sEMG compression short technology. Results: During the maximal exercise test, there were significant positive relationships between Muscle Load and all physiological measures (p < 0.001 for all) and significant negative relationships between sEMG frequency and Muscle Load and all physiological measures of fatigue (p < 0.001 for all). Conclusions: Using sEMG wearable compression short technology may be a useful way to measure and monitor muscle strain and fatigue, primarily outside of a laboratory setting.