VO2 Measurements Research Articles

Características morfo-funcionales y motoras en jóvenes futbolistas como criterio de orientación y selección deportiva

Se realizó un estudio descriptivo, comparativo y transversal para identificar características morfo-funcionales y motoras de 193 futbolistas (14-20 años) de Millonarios (Bogotá) y América (Cali), con el fin de establecer criterios de orientación y selección deportiva. Se conformaron tres grupos: G1 (n=52) nacidos entre 1991 – 1990; G2 (n=72) entre 1992 - 1993 y G3 (n=69) entre 1994 – 1995.
 El componente morfológico evaluó: dimen­siones corporales totales, somatotipo (Heath-Carter) y composición corporal (Mateigka). Para el componente motor se valoró test de Leger, Sprint (Bangsbo), salto largo, Wells, y velocidad (20-30-50 metros). El componente funcional se estableció con medición indirecta del VO2 máx, registro de FC (en reposo, para cada escalón del test de Leger y la inicial y final en cada repetición del test de Sprint).
 Los jugadores americanos presentaron un mejor desempeño en componente morfológico, con promedios superiores en todas las variables. Los componentes motor y funcional evidencian algunas diferencias en variables relacionadas con mecanismo anaeróbico a favor de América, mientras que el aeróbico sólo fue superior en G3 a favor de Millonarios.

Estimation, Rather Than Direct Measurement, of Resting Oxygen Consumption Yields Inaccurate Hemodynamic Measurements during Right Heart Catheterization

Oxygen consumption (VO2) is typically estimated rather than measured during right heart catheterization (RHC). Recent development of small portable metabolic carts has made direct measurement of resting VO2 possible. We hypothesized that estimation of VO2 might lead to significant errors in hemodynamic calculations. In this study, we compared measured and estimated VO2 and analyzed the impact on cardiac output (CO) and pulmonary vascular resistance (PVR) in patients undergoing RHC. Resting VO2 was measured in 10 transplant and 3 heart failure patients using the Innocor device at the time of right heart catheterization (VO2 ). Breath-by-breath data were averaged over 2 minutes after a 50 second equilibration period. VO2 was also estimated from the LaFarge equation (VO2 ). CO was calculated by the Fick equation using both VO2 IN (CO) and VO2 LF (CO). CO was also measured by the thermodilution method (CO). PVR was calculated utilizing CO, CO, and CO. Measured VO2 IN and calculated VO2 LF did not correlate (r5 0.42; p5 0.18). In most patients, VO2 LF significantly underestimated VO2 IN by 840% (235 6 43 vs 280 6 67 ml/min; p ! 0.05). CO was significantly higher than both CO and CO (p ! 0.05 for both). Importantly, PVR calculated using CO was significantly lower than PVR calculated using both CO and CO (p ! 0.05 for both). Portable technology allows a convenient and accurate measurement of VO2 during RHC. Estimation of VO2 yields inaccurate CO and PVR, which could adversely affect clinical decision making in patients with advanced heart failure being evaluated for heart transplantation.

The Relationship Of Cardiorespiratory And Muscular Fitness To Quality Of Life In Patients Prior To Breast Cancer Treatment

The General Functional Assessment of Cancer Therapy (FACT-G) questionnaire is a frequently used quality of life metric in patients with cancer. Evidence describing the association between measures of physical fitness and quality of life is lacking. PURPOSE: We describe the relationship between the FACT-G and its sub-components with measures of fitness in women with breast cancer prior to receiving adjuvant cancer therapies. METHODS: We recruited 22 patients (mean + SD: age 57 + 11 years, BMI 34 + 9 kg m-1, peak VO2 18.8 ml kg-1 min-1) in the ExCITE (Exercise and Cancer: Integrative Therapies and Education) trial at Henry Ford Hospital between 10/08 and 8/09. Measures of peak VO2, muscular endurance, peak torque, and leg extension one-repetition maximum (1-RM) were correlated with the total FACT-G score and its four sub-components. Pearson correlation coefficients were performed to examine the various relationships. RESULTS: Significant correlations (r) were observed between the selected fitness measures and the physical sub-component (Phy) of FACT-G (table 1). A weak, non-significant relationship was observed between these fitness measures and the social (Soc), emotional (Emo), or functional (Func) subcomponents. CONCLUSION: The physical sub-component of the FACT questionnaire has a moderately strong relationship with both peak VO2 and muscular strength. Future studies are needed to describe this relationship over the course of adjuvant cancer therapies.Table 1

Oxygen Consumption and Heart Rate Responses in Graded Exercise during Long-Duration Space Flight

Astronauts routinely perform submaximal graded exercise testing using cycle ergometry before and during International Space Station (ISS) missions. Aerobic capacity has been estimated from linear extrapolation of heart rate (HR) response and submaximal oxygen consumption (VO2). The elevated HR response to standardized exercise work rates during ISS flight typically has been interpreted as aerobic deconditioning. However, until recently VO2 has not been measured during these tests. PURPOSE: To determine if submaximal VO2 and HR measured during exercise tests on the ISS differ from preflight values as a function of time on board and of exercise intensity. METHODS: Astronauts (n=7) performed exercise tests before flight on a standard cycle ergometer and during flight on the ISS cycle ergometer. In-flight exercise tests were conducted at intervals between days 21 and 149 of the missions. The protocol for submaximal exercise tests consisted of three 5-minute stages at work rates prescribed to elicit 25, 50, and 75% of preflight peak VO2. HR was obtained from ECG and VO2 from metabolic gas analysis. Mixed modeling was used to examine the mean differences between preflight and in-flight measurements of VO2 and of HR over time and at each work rate. RESULTS: During flight, VO2 was significantly lower during the 25% and higher during the 75% exercise stages but did not differ from preflight VO2 at the 50% stage. These differences were consistent across in-flight time points. HR was unchanged from preflight HR at the 25% stage of exercise, although the HR at this stage tended to lower as flight duration increased. At the 50% and 75% stages, HR was elevated early during the missions but did not differ from preflight values later during flight. CONCLUSIONS: The preflight relationship between VO2 and work rate is not maintained during flight, perhaps because of microgravity and/or differences between the ergometers. The changing HR responses across mission duration, some of which do not parallel the VO2 findings, may indicate an acute adaptation early during flight that normalizes later during the missions, and/or an exercise training effect during flight. Thus, estimating aerobic capacity during flight by using only HR responses to submaximal work rates may result in erroneous conclusions. Supported by NASA Contract NAS 9-02078

Influence of priming exercise on muscle [PCr] and pulmonary O2 uptake dynamics during ‘work-to-work’ knee-extension exercise

Metabolic transitions from rest to high-intensity exercise were divided into two discrete steps (i.e., rest-to-moderate-intensity (R-->M) and moderate-to-high-intensity (M-->H)) to explore the effect of prior high-intensity 'priming' exercise on intramuscular [PCr] and pulmonary VO₂ kinetics for different sections of the motor unit pool. It was hypothesized that [PCr] and VO₂ kinetics would be unaffected by priming during R-->M exercise, but that the time constants (tau) describing the fundamental [PCr] response and the phase II VO₂ response would be significantly reduced by priming for M-->H exercise. On three separate occasions, six male subjects completed two identical R-->M/M-->H 'work-to-work' prone knee-extension exercise bouts separated by 5min rest. Two trials were performed with measurement of pulmonary VO₂ and the integrated electromyogram (iEMG) of the right m. vastus lateralis. The third trial was performed within the bore of a 1.5-T superconducting magnet for (31)P-MRS assessment of muscle metabolic responses. Priming did not significantly affect the [PCr] or VO₂ tau during R-->M ([PCr] tau Unprimed: 24+/-16 vs. Primed: 22+/-14s; VO₂ tau Unprimed: 26+/-8 vs. Primed: 25+/-9s) or M-->H transitions ([PCr] tau Unprimed: 30+/-5 vs. Primed: 32+/-7s; VO₂ tau Unprimed: 37+/-5 vs. Primed: 38+/-9s). However, it did reduce the amplitudes of the [PCr] and VO₂ slow components by 50% and 46%, respectively, during M-->H (P<0.05 for both comparisons). These effects were accompanied by iEMG changes suggesting reduced muscle fiber activation during M-->H exercise after priming. It is concluded that the tau for the initial exponential change of muscle [PCr] and pulmonary VO₂ following the transition from moderate-to-high-intensity prone knee-extension exercise is not altered by priming exercise.

Elucidating the sources of enhanced oxygen consumption during early reperfusion following skeletal muscle ischemia in the rat spinotrapezius muscle

Prolonged skeletal muscle ischemia is disruptive to cellular respiration. Upon reperfusion, the metabolic rate of the affected tissue is altered in a fashion dependent on the duration and totality of ischemia. This can be used as an indicator of the changes undergone in cellular metabolism. We have employed Phosphorescence Quenching Microscopy in conjunction with a flow‐arrest technique to assess the influences of external, pressure‐induced 1‐ to 30‐min focal ischemic durations on interstitial oxygenation (PO2) and the consumption of oxygen (VO2) in spinotrapezius muscles of SD rats. VO2 was assessed by the rate of PO2 decline during brief flow‐arrest compressions during reperfusion. Our tests of this intermittent compression technique have indicated that 5 s of flow‐arrest followed by 15 s of flow restoration allow for measurement of VO2 without compromising baseline or reperfusion recovery of interstitial PO2. Our preliminary studies show a ~5‐fold increase in VO2 following 30 min of ischemia, which then follows an exponential decay over several minutes back to baseline levels. Chemical modification of mitochondrial function, [NO], and [ROS] are expected to reveal the sources of this VO2 spike and how they influence the return to baseline. As hypoxia is central to I/R injury, a description of mitochondrial function during this insult will be helpful.

Energy cost of walking: A comparison of two recognised methods for defining steady state in a group of unimpaired children and children with cerebral palsy

Measurement of VO 2 based ‘energy cost of walking’ indices provide quantitative information that can be used clinically to ascertain progress and relative functional impairment in pathology. The accuracy and validity of these indices relies on being able to identify periods of steady state conditions, since it is only in steady state that there is a direct and predictable relationship between VO 2 consumption and energy expenditure. This paper presents a comparison of two new mathematically based approaches that have recently gained recognition as methods for identifying steady state during an energy cost assessment. The first applies a mathematically defined threshold for steady state within a (non-treadmill) walking trial. This method is compared with a statistically based approach that relies on the calculation of the correlation coefficient, Kendall's Tau to define steady state data. To examine the impact of both methods on the calculation of the energy cost of walking, each was applied to the calculation of two oxygen based energy cost of walking parameters, the non-dimensional net oxygen cost and the net oxygen cost with speed normalised to height in a cohort of unimpaired subjects and children with cerebral palsy. The results revealed that overall there were no clinically significant differences between the two methods. It is suggested that the methods can be used interchangeably to calculate the energy cost of walking.

Comparison of the Cosmed K4b2 Portable Metabolic System in Measuring Steady-State Walking Energy Expenditure

Background and AimsRecent introduction of the Cosmed K4b2 portable metabolic analyzer allows measurement of oxygen consumption outside of a laboratory setting in more typical clinical or household environments and thus may be used to obtain information on the metabolic costs of specific daily life activities. The purpose of this study was to assess the accuracy of the Cosmed K4b2 portable metabolic analyzer against a traditional, stationary gas exchange system (the Medgraphics D-Series) during steady-state, submaximal walking exercise.MethodsNineteen men and women (9 women, 10 men) with an average age of 39.8 years (±13.8) completed two 400 meter walk tests using the two systems at a constant, self-selected pace on a treadmill. Average oxygen consumption (VO2) and carbon dioxide production (VCO2) from each walk were compared.ResultsIntraclass Correlation Coefficient (ICC) and Pearson correlation coefficients between the two systems for weight indexed VO2 (ml/kg/min), total VO2 (ml/min), and VCO2 (ml/min) ranged from 0.93 to 0.97. Comparison of the average values obtained using the Cosmed K4b2 and Medgraphics systems using paired t-tests indicate no significant difference for VO2 (ml/kg/min) overall (p = 0.25), or when stratified by sex (p = 0.21 women, p = 0.69 men). The mean difference between analyzers was – 0.296 ml/kg/min (±0.26). Results were not significantly different for VO2 (ml/min) or VCO2 (ml/min) within the study population (p = 0.16 and p = 0.08, respectively), or when stratified by sex (VO2: p = 0.51 women, p = 0.16 men; VCO2: p = .11 women, p = 0.53 men).ConclusionThe Cosmed K4b2 portable metabolic analyzer provides measures of VO2 and VCO2 during steady-state, submaximal exercise similar to a traditional, stationary gas exchange system.

Recommendations for Improved Data Processing from Expired Gas Analysis Indirect Calorimetry

There is currently no universally recommended and accepted method of data processing within the science of indirect calorimetry for either mixing chamber or breath-by-breath systems of expired gas analysis. Exercise physiologists were first surveyed to determine methods used to process oxygen consumption ((.)VO2) data, and current attitudes to data processing within the science of indirect calorimetry. Breath-by-breath datasets obtained from indirect calorimetry during incremental exercise were then used to demonstrate the consequences of commonly used time, breath and digital filter post-acquisition data processing strategies. Assessment of the variability in breath-by-breath data was determined using multiple regression based on the independent variables ventilation (VE), and the expired gas fractions for oxygen and carbon dioxide, FEO2 and FECO2, respectively. Based on the results of explanation of variance of the breath-by-breath (.)VO2 data, methods of processing to remove variability were proposed for time-averaged, breath-averaged and digital filter applications. Among exercise physiologists, the strategy used to remove the variability in (.)VO2 measurements varied widely, and consisted of time averages (30 sec [38%], 60 sec [18%], 20 sec [11%], 15 sec [8%]), a moving average of five to 11 breaths (10%), and the middle five of seven breaths (7%). Most respondents indicated that they used multiple criteria to establish maximum ((.)VO2 ((.)VO2max) including: the attainment of age-predicted maximum heart rate (HR(max)) [53%], respiratory exchange ratio (RER) >1.10 (49%) or RER >1.15 (27%) and a rating of perceived exertion (RPE) of >17, 18 or 19 (20%). The reasons stated for these strategies included their own beliefs (32%), what they were taught (26%), what they read in research articles (22%), tradition (13%) and the influence of their colleagues (7%). The combination of VE, FEO2 and FECO2 removed 96-98% of (.)VO2 breath-by-breath variability in incremental and steady-state exercise (.)VO2 data sets, respectively. Correction of residual error in (.)VO2 datasets to 10% of the raw variability results from application of a 30-second time average, 15-breath running average, or a 0.04 Hz low cut-off digital filter. Thus, we recommend that once these data processing strategies are used, the peak or maximal value becomes the highest processed datapoint. Exercise physiologists need to agree on, and continually refine through empirical research, a consistent process for analysing data from indirect calorimetry.

Peak Oxygen Consumption Measured during the Stair-Climbing Test in Lung Resection Candidates

Background: The stair-climbing test is commonly used in the preoperative evaluation of lung resection candidates, but it is difficult to standardize and provides little physiologic information on the performance. Objective: To verify the association between the altitude and the VO_2peak measured during the stair-climbing test. Methods: 109 consecutive candidates for lung resection performed a symptom-limited stair-climbing test with direct breath-by-breath measurement of VO_2peak by a portable gas analyzer. Stepwise logistic regression and bootstrap analyses were used to verify the association of several perioperative variables with a VO_2peak <15 ml/kg/min. Subsequently, multiple regression analysis was also performed to develop an equation to estimate VO_2peak from stair-climbing parameters and other patient-related variables. Results: 56% of patients climbing <14 m had a VO_2peak <15 ml/kg/min, whereas 98% of those climbing >22 m had a VO_2peak >15 ml/kg/min. The altitude reached at stair-climbing test resulted in the only significant predictor of a VO_2peak <15 ml/kg/min after logistic regression analysis. Multiple regression analysis yielded an equation to estimate VO_2peak factoring altitude (p < 0.0001), speed of ascent (p = 0.005) and body mass index (p = 0.0008). Conclusions: There was an association between altitude and VO_2peak measured during the stair-climbing test. Most of the patients climbing more than 22 m are able to generate high values of VO_2peak and can proceed to surgery without any additional tests. All others need to be referred for a formal cardiopulmonary exercise test. In addition, we were able to generate an equation to estimate VO_2peak, which could assist in streamlining the preoperative workup and could be used across different settings to standardize this test.

Exercise induced hyperglycaemia in the absence of diabetes

Exercise induced hyperglycaemia in the absence of diabetes

Growth of Metal Oxide Nanowires from Supercooled Liquid Nanodroplets

Nanometer-sized liquid droplets formed at temperatures below the bulk melting point become supercooled as they grow through Ostwald ripening or coalescence and can be exploited to grow nanowires without any catalyst. We used this simple approach to synthesize a number of highly crystalline metal oxide nanowires in a chemical or physical vapor deposition apparatus. Examples of nanowires made in this way include VO(2), V(2)O(5), RuO(2), MoO(2), MoO(3), and Fe(3)O(4), some of which have not been previously reported. Direct evidence of this new mechanism of nanowire growth is found from in situ 2-dimensional GISAXS (grazing incidence small angle X-ray scattering) measurements of VO(2) nanowire growth, which provides quantitative information on the shapes and sizes of growing nanowires as well as direct evidence of the presence of supercooled liquid droplets. We observe dramatic changes in nanowire growth by varying the choice of substrate, reflecting the influence of wetting forces on the supercooled nanodroplet shape and mobility as well as substrate-nanowire lattice matching on the definition of nanowire orientation. Surfaces with defects can also be used to pattern the growth of the nanowires. The simplicity of this synthesis concept suggests it may be rather general in its application.

Relationship between postabsorptive respiratory exchange ratio and plasma free fatty acid concentrations

The relationship between overnight postabsorptive (fasting) respiratory exchange ratio (RER) and plasma FFA concentrations was addressed using data from three separate protocols, each of which involved careful control of the antecedent diet. Protocol 1 examined the relationship between fasting RER and the previous daytime RER. In Protocol 2 fasting, RER and plasma palmitate concentrations were measured in 29 women and 31 men (body mass index <30 kg.m(-2)). Protocol 3 analyzed data from Nielsen et al. (Nielsen, S., Z. K. Guo, J. B. Albu, S. Klein, P. C. O'Brien, M. D. Jensen. 2003. Energy expenditure, sex and endogenous fuel availability in humans. J. Clin. Invest. 111: 981-988.) to understand how fasting RER and palmitate concentrations relate within individuals during four consecutive measurements. The results were as follows: 1) Fasting RER was correlated (r = 0.74, P < 0.001) with the previous day's average RER, and less so with RER variability. 2) Fasting RER was correlated (r = -0.39, P = 0.007) with fasting plasma palmitate concentrations. 3) The pattern of the RER/palmitate relationship was similar within individuals and between individuals; a negative slope was observed significantly more often than a positive slope (chi(2) test; P < 0.001). Our findings suggest that, despite a fixed food quotient, the slight departures from energy equilibrium in a controlled General Clinical Research Center environment can effect plasma FFA concentrations. We suggest that including indirect calorimetry as part of FFA metabolism studies may aid in data interpretation.

Oxygen Consumption, Shuttle Walking Test and the Evaluation of Lung Resection

Background: Assessment of peak oxygen uptake (VO₂) is recommended in the evaluation of patients with borderline pulmonary function as VO₂ is the strongest independent predictor of postoperative pulmonary complications. However, the measurement of VO₂ requires expensive equipment not available in many medical facilities. The shuttle walking test (SWT) has been proposed to be used as a screening tool prior to performing a cardiopulmonary exercise test. Although an association exists between SWT distance and VO₂, only one small study directly measured VO₂ during the SWT. Objectives: The aim of this study was to further validate the VO₂-SWT association by directly measuring VO₂ during SWT in a larger cohort of patients with stable chronic obstructive pulmonary disease (COPD). Methods: Fifty stable COPD patients with mild/severe disease were studied. Each patient performed an SWT while wearing a validated portable metabolic monitor. Results: Mean VO₂ (ml/kg/min) measured after each finalized minute of the SWT was (95% confidence interval): 6 (5–7), 9 (8–10), 11 (10–12), 13 (11–14), 15 (14–16), 18 (16–20) and 21 (18–26) for minutes 1–7, respectively. Patients that completed the British Thoracic Society-recommended 25 shuttles (5 min or 250 m) in the SWT had a mean VO₂ of 15 (14–16). The positive predictive value for walking 25 shuttles (predicting a VO₂ of ≧15ml/kg/min) was 90% and the negative predictive value was 90%. Conclusions: Our findings validate the association between VO₂ and SWT distance and facilitate the interpretation of the test in general practice, particularly when deciding the candidacy of a patient for surgical resection.

Effects of short-term endurance exercise training on vascular function in young males

We investigated effects of 6 days of endurance exercise training [cycling at 65% of peak oxygen consumption (VO(2peak)) for 2 h a day on six consecutive days] on vascular function in young males. Measures of VO(2peak), arterial stiffness, calf vascular conductance and heart rate variability were obtained pre- and post-training. Indices of arterial stiffness were obtained by applanation tonometry to determine aortic augmentation index normalized to a heart rate of 75 bpm (AI(x) at 75 bpm), and central and peripheral pulse wave velocity (CPWV, PPWV). Resting and maximal calf vascular conductances were calculated from concurrent measures of blood pressure and calf blood flow using venous occlusion strain-gauge plethysmography. Time and frequency domain measures of heart rate variability were obtained from recording R-R intervals during supine and standing conditions. Both CPWV (5.9 +/- 0.8 vs. 5.4 +/- 0.8 m/s) and PPWV (9.7 +/- 0.8 vs. 8.9 +/- 1.3 m/s) were reduced following the training program. No significant changes were observed in AI(x) at 75 bpm, vascular conductance, heart rate variability or VO(2peak). These data indicate that changes in arterial stiffness independent of changes in heart rate variability or vascular conductance can be achieved in healthy young males following only 6 days of intense endurance exercise.

Effect Of Moderate Hypoxia On The Power-endurance Relationship

PURPOSE: The asymptote of the hyperbolic power-endurance relationship (Critical Power, CP) has been suggested to represent a sustainable power output using renewable aerobic energy. Work rates above CP would result in blood [lactate] rising until peak VO2 is attained and exhaustion would occur when the curvature of the power-endurance relationship, defined as a fixed Anaerobic Work Capacity (AWC), is totally depleted. Since CP is dependent on aerobic energy supply, we tested the hypothesis that it should be reduced systematically under hypoxia while AWC would remain unaltered. METHODS: Seventeen subjects (8 males; age: 37 ± 3; mass: 71 ± 2 kg) performed a ramp test to determine peak VO2, and three to four constant-load tests to exhaustion in order to model the linear P-t-1 relationship (using a 2-parameter model where CP is the intercept, and AWC the slope). All tests were performed in a random order under moderate hypoxia (FiO2=0.15; pre-exercise SaO2 of 93.5 ± 0.8%) and normoxia (pre-exercise SaO2 of 98.3 ± 0.3%) on a SRM cycle ergometer with VO2 measurement using a breath-by-breath analyzer (Ergocard; Medi-Soft). Paired t-tests were performed to identify differences. Relationships were explored using the Spearman correlation coefficient. The significance was set at P<0.05. RESULTS: Peak VO2 (3.55 ± 0.17 L.min-1vs 3.11 ± 0.15 L.min-1; P<0.01) and CP (225 ± 10W vs 193 ± 8 W; 2.86 ± 0.13 L.min-1 vs 2.45 ± 0.12 L.min-1; P<0.01) were both significantly reduced by hypoxia. The decrease in CP (-14 ± 2%; range from 1 to -26%) and peak VO2 (-12 ± 1% decrease; range from -1 to -21%) were significantly correlated (r=0.82; P<0.05). AWC was not significantly different under hypoxia (11.8 ± 1.2 kJ vs 12.2 ± 0.9 kJ; P>0.05) with the changes in AWC (+12 ± 8%; range from +60 to -36%) being highly correlated with the changes in CP (r=-0.80; P<0.05). CONCLUSION: The present study demonstrates the aerobic nature of the intercept of the P-t-1 relationship. A reduction in the systemic O2 transport systematically affects CP, with 67% of its change being explained by peak VO2 changes. The extreme changes in AWC in individuals whose CP were most affected by hypoxia, challenges the current interpretation of this parameter.

Compendium Of Physical Activities Underestimates Individual Energy Expenditure Of Healthy Participants

PURPOSE: This study evaluated the MET values presented in the CPA for estimating energy expenditure and intensity during laboratory physical activities in a group of fit subjects. METHODS: 10 Subjects, 5 women and 5 men, performed 12 exercise bouts in the laboratory. Activities, including walking and jogging, cycling, and resting assessments, were measured at steady state values. Calisthenics included a specific number of repetitions, but did not reach steady state. Oxygen uptake was measured through indirect calorimetry. RESULTS: Subjects (N=10) represented healthy adults of different ages (28-64 years). The population was in good health, with the average age of 39 years, an average BMI of 24 kg/m2, and an average resting metabolic rate of 3.6 ml/kg/min. The resting metabolic measurements were significantly (P<.000) higher than the CPA prediction of 1.0 MET. Sitting, walking (3.0 mph), jogging (5.0 mph), and cycling (100 watts) had higher measured MET values (P<.000) than CPA. Graded walking measurements matched the CPA "3.5 mph walking uphill" at 3.0 mph and 6% grade, but were much higher at 3.0 mph and 9% grade. Three cycling stages were all higher (P<.000) than similar CPA values (8.7 METs vs 5.5 METs at 100W). For the entire time of steady-state exercise, there was a significantly (p=.015) higher energy expenditure for the group than what was predicted by the CPA (31 kcals in 26 min), but there was a very strong correlation of.959 (P=.000) between the measured and CPA predicted values. CONCLUSIONS: The difference in predicted and measured MET values could be due to individual differences in resting metabolic rate, body composition, and age. Higher METs measured during cycling stages could imply a misclassification of the intensity when using the CPA as a reference. Good correlation between the VO2 measurements and the prediction suggest that using the CPA values could be more accurate in this fit sample if they were corrected for variation in resting metabolic rate. Perhaps the proposed updates to the CPA for specific sub-groups will increase the usability of the CPA for calculating individual energy expenditure.

Development Of A Metabolic Equation For Nustep® Recumbent Stepper Exercise In Older Adults

Exercise professionals frequently rely upon metabolic equations to prescribe exercise intensity and to estimate the energy expenditure of different exercise modalities (Franklin, 2000). To date there has been no research performed to develop accurate prediction equations for the NuStep® (NS) recumbent stepper. PURPOSE: The purpose of this study was to develop an accurate metabolic equation for estimating steady-state VO2 during submaximal NS exercise.FIGUREMETHODS: Forty male and female participants (mean ± SD, age: 64.0 ± 6.5 yr.; height: 170.1 ± 9.1 cm; weight: 85.7 ± 19.9 kg) performed two randomized testing sessions. Each session consisted of six stages with combinations of four workloads (1, 3, 5, and 7) at 3 cadences (60, 80, and 100 steps/ min). Steady-state VO2 measurements from the last 2 min of each workload were used to develop a metabolic prediction equation for NS exercise. RESULTS: Multiple regression analysis to predict steady-state VO2 from NS workload (W), NS steps/min (s/min), and subject body mass resulted in the following model (R2 =.733): Steady-state VO2 = 3.5 - 0.53(W*s/min) + 0.92(s/min) + 0.16(wt). The standard error of the estimate (SEE) and total error (TE) for the prediction of steady-state VO2 under all NS workload conditions were 2.3 mL/kg/min and 2.4 mL/kg/min respectively (see Figure). The correlation coefficient between predicted VO2 and measured VO2 values was significant (p <.05), r = 0.86. CONCLUSION: SEE and TE values for the developed NS metabolic equation are similar to those reported in previous studies investigating the accuracy of metabolic equations for other exercise modalities. These findings support the use of the equation developed in the present study to predict steady-state VO2 for NS exercise.

Fin Swimming Improves Respiratory Gas Exchange

Data in the literature suggest that compared to dry-land exercise fin swimming might delay the activation of the anaerobic metabolism. To verify this hypothesis, we explored indirect indices such as the oxygen pulse (VO(2)/HR), carbon dioxide production (VCO(2)), and ventilatory threshold, comparing fin swimming exercise to dry-land cycling. Thirteen participants, experienced or inexperienced in fin swimming, completed an incremental fin swimming exercise and a maximal exercise on a cycloergometer with breath-by-breath measurements of heart rate (HR), ventilation (VE), tidal volume (VT), VO(2), VCO(2), and VO(2)/HR and determination of the ventilatory threshold and maximal oxygen uptake (VO(2)max). Compared to dry-land cycling exercise, fin swimming resulted in elevated or absent ventilatory threshold. Although VO(2)max did not differ in either condition, in fin swimming the maximal HR value was lower (-18%, p=0.0072), maximal VO(2)/HR higher (+20%, p=0.0325), and maximal VCO(2) lower (-17%, p=0.0071). We also measured significant reduction of VE, VT, and HR variations for the same VO(2) increase. This study suggests that the anaerobic muscle metabolism might be delayed in fin swimming. An attenuated chemoreflex drive to the heart and respiratory centres exerted by muscle metabolites might explain the depressed cardiopulmonary response to fin swimming.

METHODS FOR STUDYING THE PHYSIOLOGY OF KIDNEY OXYGENATION

1. An improved understanding of the regulation of kidney oxygenation has the potential to advance preventative, diagnostic and therapeutic strategies for kidney disease. Here, we review the strengths and limitations of available and emerging methods for studying kidney oxygen status. 2. To fully characterize kidney oxygen handling, we must quantify multiple parameters, including renal oxygen delivery (DO2) and consumption (VO2), as well as oxygen tension (Po2). Ideally, these parameters should be quantified both at the whole-organ level and within specific vascular, tubular and interstitial compartments. 3. Much of our current knowledge of kidney oxygen physiology comes from established techniques that allow measurement of global kidney DO2 and VO2, or local tissue Po2. When used in tandem, these techniques can help us understand oxygen mass balance in the kidney. Po2 can be resolved to specific tissue compartments in the superficial cortex, but not deep below the kidney surface. We have limited ability to measure local kidney tissue DO2 and VO2. 4. Mathematical modelling has the potential to provide new insights into the physiology of kidney oxygenation, but is limited by the quality of the information such models are based on. 5. Various imaging techniques and other emerging technologies have the potential to allow Po2 mapping throughout the kidney and/or spatial resolution of Po2 in specific renal tissues, even in humans. All currently available methods have serious limitations, but with further refinement should provide a pathway through which data obtained from experimental animal models can be related to humans in the clinical setting.