Measurement Of Oxygen Uptake Research Articles

Dead tired: evaluating the physiological status and survival of neonatal reef sharks under stress.

Marine protected areas (MPAs) can protect shark populations from targeted fisheries, but resident shark populations may remain exposed to stressors like capture as bycatch and environmental change. Populations of young sharks that rely on shallow coastal habitats, e.g. as nursery areas, may be at risk of experiencing these stressors. The purpose of this study was to characterize various components of the physiological stress response of neonatal reef sharks following exposure to an exhaustive challenge under relevant environmental conditions. To accomplish this, we monitored markers of the secondary stress response and measured oxygen uptake rates ( ) to compare to laboratory-derived baseline values in neonatal blacktip reef (Carcharhinus melanopterus) and sicklefin lemon sharks (Negaprion acutidens). Measurements occurred over three hours following exposure to an exhaustive challenge (gill-net capture with air exposure). Blood lactate concentrations and pH deviated from baseline values at the 3-h sample, indicating that both species were still stressed 3 h after capture. Evidence of a temperature effect on physiological status of either species was equivocal over 28-31°C. However, aspects of the physiological response were species-specific; N. acutidens exhibited a larger difference in blood pH relative to baseline values than C. melanopterus, possibly owing to higher minimum . Neither species experienced immediate mortality during the exhaustive challenge; although, single instances of delayed mortality were documented for each species. Energetic costs and recovery times could be extrapolated for C. melanopterus via respirometry; sharks were estimated to expend 9.9 kJ kg-1 (15% of energy expended on daily swimming) for a single challenge and could require 8.4 h to recover. These data suggest that neonatal C. melanopterus and N. acutidens are resilient to brief gill-net capture durations, but this was under a narrow temperature range. Defining species' vulnerability to stressors is important for understanding the efficacy of shark conservation tools, including MPAs.

Deconditioning, fatigue and impaired quality of life in long-term survivors after allogeneic hematopoietic stem cell transplantation.

Long-term survivors after allogeneic hematopoietic stem cell transplantation (allo-HSCT) are at high risk for treatment-related adverse events, that may worsen physical capacity and may induce fatigue and disability. The aims of this prospective study were to evaluate exercise capacity in allotransplant survivors and its relationship with fatigue and disability. Patient-reported outcomes and exercise capacity were evaluated in 71 non-relapse patients 1 year after allo-HSCT, using validated questionnaires, cardiopulmonary exercise testing (CPET) with measure of peak oxygen uptake (peakVO2) and deconditioning, pulmonary function testing, echocardiography and 6-min walk test. A high proportion (75.4%) of allo-HSCT survivors showed abnormal cardiopulmonary exercise testing parameters as compared to predicted normal values, including 49.3% patients who exhibited moderate to severe impairment in exercise capacity and 37.7% patients with physical deconditioning. PeakVO2 values were not accurately predicted by 6-min walk distances (r = 0.53). Disability and fatigue were strongly associated with decreased peakVO2 values (p = 0.002 and p = 0.008, respectively). Exercise capacity was reduced in most allo-HSCT long-term survivors. Because reduced exercise capacity was associated with fatigue, disability and a decrease in quality of life, cardiopulmonary exercise testing should be performed in every patient who reports fatigue and disability.

Bisphenol A, phthalate metabolites and glucose homeostasis in healthy normal-weight children.

IntroductionBisphenol A and several of the most commonly used phthalates have been associated with adverse metabolic health effects such as obesity and diabetes. Therefore, we analyzed these man-made chemicals in first morning urine samples from 107 healthy normal-weight Danish children and adolescents.MethodThis was a cross-sectional study. Participants were recruited as part of the Copenhagen Puberty Study. The subjects were evaluated by an oral glucose tolerance test (OGTT), a dual-energy X-ray absorptiometry (DXA) scan, direct oxygen uptake measurement during cycle ergometry and fasting blood samples. First morning urine was collected and phthalate metabolites and BPA were measured by liquid chromatography-tandem mass spectrometry (LC–MS/MS) with prior enzymatic deconjugation. Individual chemical concentrations were divided into tertiles and analyzed in relation to biological outcome.ResultsChildren in the lowest tertile of urinary BPA had significantly higher peak insulin levels during OGTT (P = 0.01), lower insulin sensitivity index (P < 0.01), higher leptin (P = 0.03), triglyceride (P < 0.01) and total cholesterol levels (P = 0.04), lower aerobic fitness (P = 0.02) and a tendency toward higher fat mass index (P = 0.1) compared with children in the highest tertile for uBPA. No significant differences in anthropometrics, body composition or glucose metabolism were associated with any of the phthalate metabolites measured.ConclusionThis pilot study on healthy normal-weight children suggests an inverse association between BPA and insulin resistance. Our findings contrast other cross-sectional studies showing a positive association for BPA, which may be due to confounding or reverse causation because diet is an important source of both BPA exposure and obesity.

Open-circuit respirometry: a historical review of portable gas analysis systems.

Scientists such as physiologists, engineers, and nutritionists have often sought to estimate human metabolic strain during daily activities and physical pursuits. The measurement of human metabolism can involve direct calorimetry as well as indirect calorimetry using both closed-circuit respirometry and open-circuit methods that can include diluted flow chambers and laboratory-based gas analysis systems. For field studies, methods involving questionnaires, pedometry, accelerometery, heart rate telemetry, and doubly labelled water exist, yet portable metabolic gas analysis remains the gold standard for most field studies on energy expenditure. This review focuses on research-based portable systems designed to estimate metabolic rate typically under steady-state conditions by critically examining each significant historical innovation. Key developments include Zuntz's 1906 innovative system, then a significant improvement to this purely mechanical system by the widely adopted Kofranyi-Michaelis device in the 1940s. Later, a series of technical improvements: in electronics lead to Wolf's Integrating Motor Pneumotachograph in the 1950s; in polarographic O2 cells in 1970-1980's allowed on-line oxygen uptake measures; in CO2 cells in 1990s allowed on-line respiratory exchange ratio determination; and in advanced sensors/computing power at the turn of the century led to the first truly breath-by-breath portable systems. Very recent significant updates to the popular Cosmed and Cortex systems and the potential commercial release of the NASA-developed 'PUMA' system show that technological developments in this niche area are still incrementally advancing.

Sex and maturity status affected the validity of a submaximal cycle test inadolescents.

This study assessed the validity and reliability of the Ekblom-Bak (EB) submaximal cycle test in adolescents and identified any sex- or maturity-related factors for prediction errors. We recruited 50 healthy subjects through a public announcement in Stockholm, Sweden, in 2016. The 27 boys and 23 girls were aged 10-15 years and in Tanner stages I-IV. They performed an EB test and incremental treadmill running test for direct measurement of maximal oxygen uptake (VO2 max). The estimation error of VO2 max was 0.09L/min. The correlation (r) was 0.86, and the standard error of the estimate (SEE) was 0.29L/min. The largest overestimation was seen in prepubertal boys (0.49L/min). The best precision of the EB test was achieved when boys in Tanner stages I and II were re-calculated using the prediction equationdeveloped for adult women. This yielded a mean difference of -0.05L/min, r=0.92 and SEE 0.23L/min, in the entire sample. The prediction error was lowered in boys, but not girls, with increasing pubertal maturity. The EB test was reasonably valid in adolescents, seemed to be related to sex and maturity status, and our findings support its use.

Development of a bacterial propionate-biosensor for anaerobic digestion monitoring.

Monitoring anaerobic digestion (AD) leachate for changes in acetate and propionate concentrations is essential for effective AD operation. In this paper the development of a novel propionate cell-based biosensor is described. A previously designed E. coli mutant (IMD Wldgy) that could selectively determine acetate concentrations in synthetic leachates, based on oxygen uptake measurements, was used as a starting point in the development of a propionate biosensor. However, the propionate-grown IMD Wldgy cells exhibited extremely low propionate:acetate O2 consumption ratios (1:2.4). Screening for alternative propionate-grown E. coli strains naturally possessing a more favourable propionate:acetate O2 consumption ratio identified strain IMD 1, which exhibited a positive ratio (1.6:1). To improve the selectivity of the strain, successive gene knockouts were performed generating the IMD 1 hldgyep mutant. However, propionate-grown IMD 1hdlgyep's O2 consumption ratio was deemed too low to be considered as a propionate detecting bio-element. It was reasoned that the mechanisms by which E. coli activates acetate had to be removed. Deleting acs (acetyl-CoA synthesase) and ackA (acetate kinase) from IMD Wldgyep, resulted in an E. coli IMD Wldgyepak knockout mutant that, when grown on propionate, produced a mean propionate:acetate O2 consumption ratio of approx. 13:1. The resulting IMD Wldgyep and IMD Wldgyepak strains, which formed the acetate- and propionate-biosensor, respectively, were capable of detecting acetate and propionate concentrations ranging from 0.05mM to 4.5mM within two-phase AD synthetic leachates.

Kinetic analysis of oxygen dynamics under a variable work rate

Measurements of oxygen uptake are central to methods for the assessment of physical fitness and endurance capabilities in athletes. Two important parameters extracted from such data of incremental exercise tests are the maximal oxygen uptake and the critical power. A commonly accepted model of the dynamics of oxygen uptake during exercise at a constant work rate comprises a constant baseline oxygen uptake, an exponential fast component, and another exponential slow component for heavy and severe work rates. We have generalized this model to variable load protocols with differential equations that naturally correspond to the standard model for a constant work rate. This provides the means for predicting the oxygen uptake response to variable load profiles including phases of recovery. The model parameters have been fitted for individual subjects from a cycle ergometer test, including the maximal oxygen uptake and critical power. The model predictions have been validated by data collected in separate tests. Our findings indicate that the oxygen kinetics for a variable exercise load can be predicted using the generalized mathematical standard model. Such models can be applied in the field where the constant work rate assumption generally is not valid.

Metabolic heterogeneity and plasticity of glioma stem cells in a mouse glioblastoma model.

Glioblastomas have been shown to rely on glycolysis as an energy source. However, recent evidence suggests that at least a subset of glioma cells with stem cell-like properties can thrive on oxidative phosphorylation. It remains unclear whether both metabolic phenotypes support tumor propagation, if they are independent, and how stable they are. The present study investigated these questions with the use of isogenic murine glioma stem cells (GSCs). GSCs were established from tumors formed by Ink4a/Arf-null, H-RasV12-expressing glioma-initiating cells that differed in extracellular acidification potential. Metabolic characteristics of GSCs were determined by measurement of glucose, oxygen, and glutamine uptake, ATP content, and lactate production. Effects of metabolic inhibitors and changes in oxygen or nutrient availability on lactate production and tumorsphere growth were also determined. GSCs were found either to consume more glucose and produce more lactate or to consume more oxygen and maintain a higher ATP content depending on the metabolic characteristics of the tumor cells of origin. The latter, mitochondrial-type GSCs increased lactate production after treatment with the oxidative phosphorylation inhibitor oligomycin or phenformin. Exposure to hypoxia also increased lactate production and expression of glycolysis-related enzymes and metabolites in mitochondrial-type GSCs in a reversible manner. Both glycolytic and mitochondrial-type energy production can sustain tumor propagation by isogenic GSCs. Whereas both phenotypes can be independent and stable, cells that rely on oxidative phosphorylation can also switch to a more glycolytic phenotype in response to metabolic stress, suggesting that plasticity is a further characteristic of GSC metabolism.

Reply to Pettitt and Jamnick's letter in reference to: Measurement of the maximum oxygen uptake V̇o2max: V̇o2peak is no longer acceptable.

to the editor: We appreciate Drs. Pettitt and Jamnick’s endorsement of our CORP and their recommendations for helping standardize the ramp test duration. We cited precedence for a maximal ramp test duration of 8–12 min ([1][1], [5][2]) to optimize extraction of four key parameters of aerobic

Short-term arrival strategies for endurance exercise performance at moderate altitude.

For sea level-based endurance athletes who compete at moderate and high altitudes, many are not logistically able to arrive at altitude weeks before the event to fully acclimatize. For those who can only arrive at altitude the night before competition, we asked if there is a physiological and performance advantage in reducing altitude exposure time to 2 h before competition. On three separate visits, 10 cyclists completed overnight laboratory exposures of: 1) a 14-h exposure to normobaric hypoxia (16.2% O2, simulating 2,500 m; 14H), 2) a 12-h exposure to normoxia, then a 2-h hypoxic exposure (2H), and 3) a 14-h exposure to normoxia (CON). Immediately following each exposure, subjects completed a 20-km cycle ergometry time trial in normoxia (CON) or 16.2% O2 (14H and 2H). Measures of plasma volume changes, sleep quality, ventilatory acclimatization, perceived exertion, oxygen uptake, and 20-km time were collected. No significant differences were observed in performance measures or perceived exertion between hypoxic trials. Plasma volume loss was significantly greater during 14H than 2H and CON. No differences in ventilatory acclimatization or sleep quality were observed between trials. Although some divergent 20-km performance responses were observed between 14H and 2H, they were not explained by the physiological measures completed. The data suggest that endurance athletes who are logistically restricted from arriving at altitude more than the evening before competition would not gain an advantage by delaying their arrival until a few hours before the competition, although unique individual responses may ultimately influence optimal arrival strategy.NEW & NOTEWORTHY For athletes who cannot arrive at altitude multiple days before an endurance competition to properly acclimatize, this study asked if shortening hypoxic exposure time to 2 h before a competition was more advantageous than arrival at altitude the evening before competition. Our data suggest that athletes who cannot arrive at altitude with adequate time for complete acclimatization can choose the short-term arrival strategy that best fits with the logistics of their travel.

The metabolic costs of walking and running up a 30-degree incline: implications for vertical kilometer foot races.

Vertical kilometer (VK) races, in which runners gain 1000m of elevation in<5000m of distance, are becoming popular. However, few studies on steep uphill running (>25°) exist. Previously, we determined that~30° is the optimal angle for uphill running, costing the least amount of metabolic energy for a specific vertical velocity. To inform the training and strategy of VK racers, we quantified the metabolic cost of walking and running at various velocities up a 30° incline. At 30°, 11 experienced runners (7M, 4 F, 30.8±7.9years, 1.71±0.08m, 66.7±9.4kg) walked and ran for 5-min trials with 5-min rest between. Starting at 0.3ms-1, we increased treadmill velocity by 0.1ms-1 for each trial until subjects could not maintain the set velocity. We measured oxygen uptake (ml O2kg-1min-1) and metabolic power (W kg-1=metabolic energy per unit time per unit body mass) and calculated metabolic costs of walking (C w) and running (C r) per unit distance (Jkg-1m-1). Oxygen uptake and metabolic power increased linearly with velocity. Between 0.3 and 0.7ms-1, C w<C r. At 0.8ms-1 there was no difference and extrapolation suggests that at faster velocities, running likely costs less than walking. On a 30° incline, metabolic power increases linearly with velocity. At speeds slower than 0.7ms-1, walking requires less metabolic power than running (Wkg-1) suggesting most VK racers should walk rather than run.

Relationship between oxygen cost of walking and level of walking disability after stroke: An experimental study.

Since physical inactivity is the major risk factor for recurrent stroke, it is important to understand how level of disability impacts oxygen uptake by people after stroke. This study investigated the nature of the relationship between level of disability and oxygen cost in people with chronic stroke. Level of walking disability was measured as comfortable walking speed using the 10-m Walk Test reported in m/s with 55 ambulatory people 2years after stroke. Oxygen cost was measured during 3 walking tasks: overground walking at comfortable speed, overground walking at fast speed, and stair walking at comfortable speed. Oxygen cost was calculated from oxygen uptake divided by distance covered during walking and reported in ml∙kg-1 ∙m-1 . The relationship between level of walking disability and oxygen cost was curvilinear for all 3 walking tasks. One quadratic model accounted for 81% (95% CI [74, 88]) of the variance in oxygen cost during the 3 walking tasks: [Formula: see text] DISCUSSION: The oxygen cost of walking was related the level of walking disability in people with chronic stroke, such that the more disabled the individual, the higher the oxygen cost of walking; with oxygen cost rising sharply as disability became severe. An equation that relates oxygen cost during different walking tasks according to the level of walking disability allows clinicians to determine oxygen cost indirectly without the difficulty of measuring oxygen uptake directly.

Simulation of oxygen uptake and leg joint reaction force during ergometer exercise under altered gravity.

Ergometers are safe devices for patients and elderly individuals, as the exercise intensity can be controlled. Moreover, ergometer exercises, which remove the load from body weight on the leg joint, would better reflect training conditions in locations where the force of gravity is lower than that on Earth, such as the International Space Station or on the surface of Mars. The purpose of this study was not only to validate an ergometer exercise model for measuring oxygen uptake and knee joint reaction force by comparison with experimental results, but also to consider a strategy for electrically stimulating leg joint muscles to modulate them under altered gravity.

An Effective, Versatile, and Inexpensive Device for Oxygen Uptake Measurement.

In the last ten years, the use of fluorescent probes developed to measure oxygen has resulted in several marketed devices, some unreasonably expensive and with little flexibility. We have explored the use of the effective, versatile, and inexpensive Redflash technology to determine oxygen uptake by a number of different biological samples using various layouts. This technology relies on the use of an optic fiber equipped at its tip with a membrane coated with a fluorescent dye (www.pyro-science.com). This oxygen-sensitive dye uses red light excitation and lifetime detection in the near infrared. So far, the use of this technology has mostly been used to determine oxygen concentration in open spaces for environmental studies, especially in aquatic media. The oxygen uptake determined by the device can be easily assessed in small volumes of respiration medium and combined with the measurement of additional parameters, such as lactate excretion by intact cells or the membrane potential of purified mitochondria. We conclude that the performance of by this technology should make it a first choice in the context of both fundamental studies and investigations for respiratory chain deficiencies in human samples.

Aerobic fitness and metabolic health in children: A clinical validation of directly measured maximal oxygen consumption versus performance measures as markers of health.

High aerobic fitness is consistently associated with a favorable metabolic health profile in children. However, measurement of oxygen uptake, regarded as the gold standard for evaluating aerobic fitness, is often not feasible. Thus, the aim of the present study was to perform a clinical validation of three measures of aerobic fitness (peak oxygen consumption [VO2peak] and time to exhaustion [TTE] determined from a graded treadmill protocol to exhaustion, and the Andersen intermittent running test) with clustered metabolic health in 10-year-old children. We included 93 children (55 boys and 38 girls) from Norway during 2012–2013 in the study. Associations between aerobic fitness and three different composite metabolic health scores (including lipoprotein subgroup particle concentrations, triglyceride, glucose, systolic blood pressure, and waist-to-height ratio) were determined by regression analyses adjusting for sex. The relationships among the measures of aerobic fitness were r = 0.78 for VO2peak vs. TTE, r = 0.63 for VO2peak vs. the Andersen test, and r = 0.67 for TTE vs. the Andersen test. The Andersen test showed the strongest associations across all markers of metabolic health (r = − 0.45 to − 0.31, p < 0.002), followed by VO2peak (r = − 0.35 to − 0.12, p < 0.256), and TTE (r = − 0.28 to − 0.10, p < 0.334). Our findings indicate that indirect measures of aerobic fitness do not stand back as markers of metabolic health status in children, compared to VO2peak. This is of great importance as good field tests provide opportunities for measuring aerobic fitness in many settings where measuring VO2peak are impossible.

Standard metabolic rate of juvenile triploid brook charr, Salvelinus fontinalis

The standard metabolic rates of similarly sized juvenile diploid and triploid brook charr were estimated by using intermittent-flow respirometry to measure oxygen uptake over a 10-day fasting period. Initial oxygen uptake rates did not differ between ploidies, but the rate of decline was slower in triploids, resulting in higher final oxygen uptake rates and, therefore, higher estimated standard metabolic rates. Based on other studies that have shown no effect of triploidy on maximum metabolic rate, this implies reduced aerobic scope in triploids.

Validity And Reliability Of A Low-cost System To Measure Oxygen Uptake During Submaximal Exercise

Measuring oxygen uptake (VO2) is the gold standard method for assessing cardiorespiratory fitness. Metabolic systems that assess VO2 require a significant financial investment. A low-cost VO2 system would increase the availability to measure cardiorespiratory fitness. PURPOSE: To assess the validity and reliability of a low-cost VO2 system consisting of a Vernier O2 sensor, CO2 sensor, spirometer, and a modified 2L BioChamber 2000 versus the Vmax Encore metabolic system (Care Fusion). METHODS: One healthy adult (55 years, 70.5kg) completed a submaximal graded exercise test on a cycle ergometer that began at a 50-Watt workload and increased by 25 Watts every 3 minutes to a maximum of 175 Watts. The participant’s expired air was captured simultaneously by the low-cost VO2 system and Vmax system. Both instruments measured flow rate (L/s), O2 (%), and CO2 (%) and were used to calculate ventilation (VE) and relative VO2. For the low-cost VO2 system, VO2 was calculated as the difference between the inspired and expired O2 fraction multiplied by VE (L/min). VE was corrected to Standard Temperature and Pressure, Dry. An independent t-test was used to test validity and an Intraclass Correlation Coefficient (ICC 3,2) was used to test reliability between the low-cost VO2 system and Vmax system. Significance was set at p <0 .05. A Bland-Altman plot was used to illustrate the individual difference scores between the low-cost VO2 system and Vmax system. RESULTS: There was no significant difference between low-cost VO2 system VO2 (21.1+10.3 ml/kg/min) and Vmax system (19.61+9.5 ml/kg/min) p = 0.388, 95% CI [-4.72, 1.85]. The low-cost VO2 system demonstrated excellent reliability across 71 measures with an average measures ICC=0.986, 95% CI [0.941,0.994] p<0.01. CONCLUSION: Findings support that a low-cost system provides valid and reliable measures of VO2 at rest and submaximal exercise conditions compared to the Vmax system. This project was not funded.

Toxicological interactions of ibuprofen and triclosan on biological activity of activated sludge

The growing use of pharmaceutical and personal care products increases their concentrations in the wastewater entering treatment plants and their levels into biological reactors. The most extended biological wastewater treatment is the activated sludge process. The toxicity of ibuprofen and triclosan, individually and combined, was studied by tracking the biological activity of the activated sludge measuring oxygen uptake rate and the inhibition of the esterase activity. Short-term exposure produced significant inhibition in oxygen uptake, with lower damage to enzymatic activity. Median effect values for oxygen uptake inhibition were 64±13mgL−1 and 0.32±0.07mgL−1 for ibuprofen and triclosan respectively using 125mgL−1 activated sludge. For the inhibition of enzymatic activity values were 633±63mgL−1 for ibuprofen and 1.94±0.32mgL−1 for triclosan. Results indicated that oxygen uptake, related to primary activity of microorganisms, was more strongly affected than the enzymatic activity associated to energy consumption. Toxicity interactions were determined using the Combination Index-isobologram method. Results showed antagonism at lower values of affected population, after which the mixtures tended to additivity and synergism. For the case of enzymatic activity, the antagonism was less marked and the additivity range was higher.

Effects of Aerobic Capacity on Arterial Stiffness in Individuals with Multiple Sclerosis

INTRODUCTIONIndividuals with Multiple Sclerosis (MS) exhibit a greater risk of cardiovascular disease than individuals without MS, and increased arterial stiffness is one possible risk factor. Higher aerobic capacity has been associated with lower arterial stiffness in healthy individuals and helps explain lower risk profiles. Individuals with MS in general have low aerobic capacities and the effect of MS may abolish expected relationships between fitness and arterial stiffness.PURPOSETo determine the relationship between peak oxygen consumption (VO2peak) and carotid arterial stiffness in individuals with MS.METHODSThirteen individuals with MS (43 ± 9 yrs; 25.0 ± 3.7 kg/m2) underwent an individualized incremental treadmill test to volitional exhaustion with measures of oxygen uptake. Carotid arterial stiffness was measured by ultrasonography prior to the treadmill test, and echo‐tracking software was used to calculate the β‐stiffness index, pressure‐strain elasticity modulus (Ep) and arterial compliance (AC). Bivariate correlations were implemented to examine the linear relationship between VO2peak and carotid arterial stiffness. Partial correlations were performed to control for body weight.RESULTSNegative correlations were observed between absolute VO2peak and β‐stiffness index, (p&lt;0.05) and Ep (p&lt;0.05), whereas a positive correlation was found with AC (p&lt;0.05). However, the significance between VO2peak and carotid stiffness variables was eliminated when controlling for body weight.CONCLUSIONThe findings suggest that aerobic capacity is negatively associated with carotid arterial stiffness and positively associated with arterial compliance, while body weight influences these relationships in an expected manner. Thus, aerobic training and/or weight loss might be an effective treatment to decrease arterial stiffness and consequently risk of cardiovascular disease in a population with MS. Arterial Stiffness Variables Absolute VO2peak Bivariate Correlation Absolute VO2peak Partial Correlation β‐stiffness index −0.604* −0.421 Ep (kPa) −0.682* −0.529 AC (mm22/kPa) 0.672* 0.508 Significant correlation: p&lt;0.05

Lower Percent Leg Muscle Mass is Associated with Reduced Ventilatory Efficiency in Sedentary Adults

A high ventilatory equivalent to carbon dioxide production (VE/VCO2) slope, or reduced ventilatory efficiency, is associated with disease severity and is a strong predictor of mortality in patients with heart failure (HF). We have demonstrated that a high VE/VCO2 slope during exercise is associated with lower %leg muscle mass in HF. This association was abolished with inhibition of skeletal muscle afferent feedback by lumbar fentanyl injections, demonstrating an important link between muscle mass, afferent feedback and VE/VCO2 slope. We hypothesized that %leg muscle mass would be associated with VE/VCO2 slope in sedentary adults.ObjectiveDetermine the relationship between %leg muscle mass and VE/VCO2 slope in sedentary (SED) and trained (TR) adults.MethodsFor 38 adults (23 SED [6M/17F], 31±8 yrs and 15 TR [9M/6F], 29±6 yrs (mean±SD)) measures of gas exchange and ventilation were collected during a treadmill maximal oxygen uptake (VO2max) test and measures of total fat, regional fat and muscle mass were done by dual X‐ray absorptiometry (DXA). Participants were classified as trained by self‐report of aerobic exercise training for at least 30 min/day, 5 days/week.ResultsIn the SED group, men had greater %leg muscle mass and VO2max, and less %leg fat mass than women (all p&lt;0.05). In the TR group, VO2max and %leg fat were similar (p&gt;0.05), but men had greater %leg muscle mass than women (p&lt;0.05). Percent leg muscle mass was greater in TR than SED (80±8 vs. 58±9%, respectively, p&lt;0.01), while %leg fat mass was lower in TR than SED (20±9 vs. 42±9%, respectively, p&lt;0.01). VO2max was greater in TR than SED (55±10 vs. 29±6 ml/kg/min, p&lt;0.01). When the TR and SED groups were combined, VO2max was associated with %leg muscle mass (r= 0.85, p&lt;0.01). The VE/VCO2 slope was similar between TR and SED groups (25±3 vs. 24±3, p=0.10), without any sex‐specific differences (p&gt;0.05). Specific to the SED group, VE/VCO2 slope was inversely associated with %leg muscle mass (r= −0.51, p=0.01) indicating the lower the %leg muscle mass, the steeper the VE/VCO2 slope. This relationship persisted with sex‐specific analysis (men: r= −0.80, p=0.05 and women: r= −0.57, p=0.02). The relationship between VE/VCO2 slope and %leg muscle mass not was not observed in the TR group overall or with sex‐specific analysis (p&gt;0.05).ConclusionsThese findings suggest that in sedentary adults, lower %leg muscle mass may contribute to a reduced ventilatory efficiency during exercise.Support or Funding InformationNIH 1R01DK098203‐01