Relative VO2 Research Articles

Analysis ofUSAWR Wheelmill VO2 Max Testing Between Classes

PURPOSE: Little is known about how elite level training can affect the Maximum Aerobic Capacity (Max VO2) testing for all functional classifications of national wheelchair rugby athletes. The primary purpose of this study was to review existing Max VO2 data between Higher Classification (HC) and Lower Classification (LC) players on the USA Wheelchair Rugby Team (USAWR). METHODS: Data was collected during the April training camp (camp1) and August training camp (camp2) at Lakeshore Foundation during the 2017 season. All athletes followed an individualized high intensity workout plan between camp1 and camp2. Athletes (n = 12) had to perform a graded VO2 max test on a unique Wheelmill ergometer during both camps to be included. Variables tested for significance included absolute VO2 (aVO2), relative VO2 (rVO2), Respiratory Exchange Ratio (RER), Heart Rate (HR), Ventilatory Equivalent (VE), and Rate of Perceived Exertion (RPE). International Wheelchair Rugby Federation classifications are set by functional ability starting at 0.5 and progress up in 0.5 increments to a max level of 3.5. For this study, classifications were grouped into those whose roles were primarily as a blocker (Class 0.5 – 1.5) and those whose roles were primarily ball handlers (class 2.0 – 3.5). RESULTS: Means for the whole team were tested for significant change between camp1 and camp2, and then between HC and LC using 2-tailed T-test (95% confidence interval). Despite whole team mean aVO2 and mean rVO2 was not significantly changed, whole team mean VE significantly increased from camp1 to camp2 (64.92 L/min + 9.5601, p=0.0146), as did RER (1.0750 + 0.0636, p=0.0387). Significant rVO2 Max changes occurred among LC athletes (17.9300 mL/kg/min + 1.1172, p=0.0246) and with aVO2 Max (1.5000 L/min + 0.0990, p=0.0346), but no significant changes occurred among HC group. CONCLUSION: Analysis results showed significant improvements in maximum achieved VE and RER variables between camp1 and camp2 in elite wheelchair rugby athletes. When separated into LC and HC groups, only LC showed significant improvements in rVO2 and aVO2. This could indicate that elite USAWR training methods are more effectively improving performance in athletes with lower classifications than in their higher classification counterparts.

Application Of The ActiGraph GT9X IMU For The Assessment Of Turning During Walking And Running

Rotational movements, such as turning, can significantly increase energy expenditure (EE) during ambulatory activity. Gyroscope and magnetometer sensors can quantify rotational motion, which provides additional information on movement beyond linear acceleration that is provided by only using an accelerometer. PURPOSE: The purpose of this study was to examine the use of the ActiGraph GT9X gyroscope and magnetometer for detecting turns and quantifying turn degree during walking and running. METHODS: Participants (N=17) completed pivot trials, treadmill walking and running (TM; 3 to 6 mph) and four turn conditions (i.e. 45°, 90°, 135°, and 180°) during over- ground walking and running (OG). Pivot and TM trials were completed for 1-min and 6-min, respectively. Turn frequency was constant (10 turns/min) for all OG trials. A GT9X was placed on the left hip and a Cosmed K4b2 was used to measure EE. Raw GT9X gyroscope and magnetometer data were processed through various low-pass filter frequencies (0.25 Hz to 2.0 Hz). TM and pivot trials were used to develop thresholds for turn detection using the gyroscope and magnetometer data and the OG trials were used for cross-validation. K4b2 data (VO2) were averaged over 30-s periods and converted to relative VO2 (ml/kg.min). Linear mixed models were used to compare actual and predicted number of turns, measured and predicted turn degree, and differences in VO2 across OG conditions. RESULTS: There were no main effects for speed or turn condition on turn detection when filtering the gyroscope at 0.25 Hz (p>0.05). A speed main effect was present when filtering the magnetometer at 0.75 Hz (p<0.001). 0.25 Hz (gyroscope) and 0.75 Hz (magnetometer) filters resulted in 100.5%±4.4% and 96.9%±45.4% of turns detected, respectively. Using the gyroscope, turn degree was estimated to within approximately 2.2° for all turn conditions (p<0.001). In general, the VO2 of walking and running was significantly greater during 135° and 180° turn conditions compared to 0-90° turn conditions (p<0.05). CONCLUSION: The GT9X gyroscope, when low-pass filtered at 0.25 Hz, can be used to detect the number of turns and estimate turn degree. The magnetometer was only useful for detecting the number of turns. Future work should explore the gyroscope use for turn detection during activities other than walking and running.

Children with severe burn injury do not display sex differences for exercise capacity and exercise induced training adaptations

BackgroundChildren with severe burn injury sometimes undergo exercise training as part of their rehabilitation. Others have reported that females have a 50% increased risk of death from burn injury compared to males. However, whether exercise capacity and exercise induced training adaptations differ between boys and girls is unknown.PurposeThis project tested the hypothesis that girls with burn injury would have lower strength and aerobic exercise capacity compared to burned boys, and that exercise training rehabilitation (RET) adaptations would likewise differ between groups.MethodsSeverely burned girls (n=25) and boys (n=26) were matched for age, body morphology (means±SD; 13±3 yrs, 150±15 cm, 53±14 kg; each P≥0.71) and for burn injury (54±20% total body surface area burn, P=0.82). Strength (peak torque) and cardiorespiratory fitness (peak VO2) were normalized to lean body mass (LBM) and analyzed as a relative percentage of age‐sex matched non‐burned children (girls 13 yrs, n=25, boys 13 yrs, n=26). Submaximal oxygen uptake (VO2) and heart rate (HR) were expressed as a percentage of peak values and compared to their sex‐ matched non‐burned counterpart during the first 4 stages of the modified Bruce protocol. At discharge (DC) and after an aerobic and resistance rehabilitation exercise training (RET) program, 2‐way factorial ANOVA assessed interaction and main effects of group × time for peak exercise and group × stage for submaximal exercise, with significance set at P&lt;0.05.ResultsGirls had longer length of hospital stay (41±23 vs. 29±13 days, P=0.02). At DC and post‐RET, LBM was lower in burned and increased similarly after RET (DC 87.3% of non‐burned values, post‐RET 92.8%; Main effect, Time P=0.017). Peak torque was not different at DC and increased similarly after RET in both groups (DC, 56±17; after RET, 77±20%; Main effect, Time P&lt;0.0001). Likewise, the improvement in peak VO2 was not different from DC to after RET between both groups (DC, 54±12 to RET, 67±13%; Main effect, Time; P&lt;0.0001). Burned children exercise at greater percentage of their peak VO2 and peak HR during submaximal exercise compared to non‐burned children (Interaction, Group × Stage, P&lt;0.0001; see Figure 1).ConclusionThese data indicate that the initial burn injury at DC or after RET does not have sex‐dependent effects on LBM, submaximal or peak exercise capacity. Exercise capacity is improved after exercise training but remains lower than non‐burned children. Differences in relative peak VO2 and peak HR may suggest the need for burn specific exercise programs for improving the efficacy and progress of a rehabilitation exercise program.Support or Funding InformationThis study was supported in part or totally by awards from NIH P50‐GM060338, NIH R01‐GM56687, R01 HD049471, 3R01HD049471‐12S1, SHC 84080, 71008, 84090, NIDILRR 90DP0043‐01‐00This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Physiological demands of daily riding gaits in jockeys.

Jockeys should maintain a high level of physical fitness to meet the physical demands of horse racing. The aim of this study was to determine the physiological requirements of the riding gaits used regularly in training. Eleven trainee jockeys performed a maximal incremental Wattbike cycle ergometer test. Mean absolute and relative oxygen uptake (VO2) and heart rate (HR) were recorded for the steady-state period during a walk, trot and canter. Energy expenditure (EE) and associated metabolic equivalent (MET) were also estimated. During a walk, trot and canter, relative mean VO2 corresponded to 15±4%, 38±6%, 47±9% of VO2peak and mean HR corresponded to 48±6%, 60±6%, 71±7% of HRpeak respectively. Mean VO2 and mean HR were significantly different amongst gaits; P≤0.001. Walking required the lowest estimated EE of 2.25±0.6 kcal.min-1 (P≤0.001; 2.4 METs;) and it was significantly lower than trotting at 5.72±1.0 kcal.min-1 (P≤0.001; 6.2 METs) and cantering at 7.10±1.8 kcal.min-1 (P≤0.001; 7.7 METs). These riding activities are associated with relatively low physiological demand and alternate modes of exercise are recommended for trainee jockeys to ensure the demands of racing are met. Future research should investigate the physical training, both riding-specific and general conditioning, jockeys perform in preparation for racing.

Using a site-specific technical error to establish training responsiveness: a preliminary explorative study.

BackgroundEven though cardiorespiratory fitness (CRF) training elicits numerous health benefits, not all individuals have positive training responses following a structured CRF intervention. It has been suggested that the technical error (TE), a combination of biological variability and measurement error, should be used to establish specific training responsiveness criteria to gain further insight on the effectiveness of the training program. To date, most training interventions use an absolute change or a TE from previous findings, which do not take into consideration the training site and equipment used to establish training outcomes or the specific cohort being evaluated. The purpose of this investigation was to retrospectively analyze training responsiveness of two CRF training interventions using two common criteria and a site-specific TE.MethodsSixteen men and women completed two maximal graded exercise tests and verification bouts to identify maximal oxygen consumption (VO2max) and establish a site-specific TE. The TE was then used to retrospectively analyze training responsiveness in comparison to commonly used criteria: percent change of >0% and >+5.6% in VO2max.ResultsThe TE was found to be 7.7% for relative VO2 max. χ2 testing showed significant differences in all training criteria for each intervention and pooled data from both interventions, except between %Δ >0 and %Δ >+7.7% in one of the investigations. Training nonresponsiveness ranged from 11.5% to 34.6%.ConclusionFindings from the present study support the utility of site-specific TE criterion to quantify training responsiveness. A similar methodology of establishing a site-specific and even cohort specific TE should be considered to establish when true cardiorespiratory training adaptations occur.

Children with severe burns display no sex differences in exercise capacity at hospital discharge or adaptation after exercise rehabilitation training

Background and objectiveFemales have a 50% increased risk of death from burn injury compared to males. However, whether exercise capacity and exercise induced training adaptations differ between burned boys and girls is unknown. This project tested the hypothesis that girls with burns have lower exercise capacity and different exercise induced training adaptations. MethodsTwenty-five girls were matched to 26 boys (mean, 95%CI; years 13 [12,14], cm 151 [143,161], kg 54 [45,63]; each P>0.05) for burn injury (% total body surface area burn, 54 [45,62]; P=0.82). Lean body mass (LBM), strength (peak torque) and cardiorespiratory fitness (peak VO2) were normalized to kg LBM and compared as a percentage of age–sex matched non-burned children (n=26 boys, years 13 [12,14]; n=25 girls, years 13 [12,14]) at discharge (DC) and after aerobic and resistance rehabilitation exercise training (RET). ResultsUsing a 2-way factorial ANOVA (group×time), we found both groups had similar 11% change in LBM (87.3% of non-burned values [82.2,92.3]) and after the RET (92.8% [87.2,98.3]; main effect, time P<0.0001). Peak torque increased similarly by 16% in both groups (% of age–sex matched non-burned DC, 55.9 [51.3,60.5]; after RET, 77.5 [72.1,82.9]; main effect, time P<0.0001). Likewise, peak VO2 increased in both groups by 15% (% of age–sex matched non-burned DC, 56.8 [52.4,61.2] to RET, 72.2 [67.6,76.8]; main effect, time; P<0.0001). Burned children exercise at greater percentage of their peak VO2 and peak HR compared to non-burned children (Interaction, group×time, P<0.0001). ConclusionThe burn injury does not have sex-dependent effects on LBM or exercise capacity in severely burn injured children. Differences in relative peak VO2 and peak HR suggest the need for burn specific exercise programs for improving the efficacy of a rehabilitation program.

The Effect of Lower-Body Positive Pressure on the Cardiorespiratory Response at Rest and during Submaximal Running Exercise.

Anti-gravity treadmills facilitate locomotion by lower-body positive pressure (LBPP). Effects on cardiorespiratory regulation are unknown. Healthy men (30 ± 8 y, 178.3 ± 5.7 cm, 70.3 ± 8.0 kg; mean ± SD) stood upright (n = 10) or ran (n = 9) at 9, 11, 13, and 15 km.h−1 (5 min stages) with LBPP (0, 15, 40 mmHg). Cardiac output (CO), stroke volume (SV), heart rate (HR), blood pressure (BP), peripheral resistance (PR), and oxygen uptake (VO2) were monitored continuously. During standing, LBPP increased SV [by +29 ± 13 (+41%) and +42 ± 15 (+60%) ml, at 15 and 40 mmHg, respectively (p < 0.05)] and decreased HR [by −15 ± 6 (−20%) and −22 ± 9 (−29%) bpm (p < 0.05)] resulting in a transitory increase in CO [by +1.6 ± 1.0 (+32%) and +2.0 ± 1.0 (+39%) l.min−1 (p < 0.05)] within the first seconds of LBPP. This was accompanied by a transitory decrease in end-tidal PO2 [by −5 ± 3 (−5%) and −10 ± 4 (−10%) mmHg (p < 0.05)] and increase in VO2 [by +66 ± 53 (+26%) and +116 ± 64 (+46%) ml.min−1 (p < 0.05)], suggesting increased venous return and pulmonary blood flow. The application of LBPP increased baroreflex sensitivity (BRS) [by +1.8 ± 1.6 (+18%) and +4.6 ± 3.7 (+47%) at 15 and 40 mmHg LBPP, respectively P < 0.05]. After reaching steady-state exercise CO vs. VO2 relationships remained linear with similar slope and intercept for each participant (mean R2 = 0.84 ± 0.13) while MAP remained unchanged. It follows that (1) LBPP affects cardiorespiratory integration at the onset of exercise; (2) at a given LBPP, once reaching steady-state exercise, the cardiorespiratory load is reduced proportionally to the lower metabolic demand resulting from the body weight support; (3) the balance between cardiovascular response, oxygen delivery to the exercising muscles and blood pressure regulation is maintained at exercise steady-state; and (4) changes in baroreflex sensitivity may be involved in the regulation of cardiovascular parameters during LBPP.

Oxygen uptake kinetics to assess cardiorespiratory fitness in obese patients

The evaluation of cardiorespiratory fitness (RCC) using maximal or peak oxygen consumption (VO2), requires a high level of effort in obese patients. We propose a method to evaluate RCC using constant and moderate loads, called VO2 kinetics (tau). To determine the relationship between tau and peak VO2 in patients with obesity. Forty patients (87% females) aged 37 ± 12 years and with a body mass index (BMI) of 34.6 ± 4.0 kg/m2, were divided into two groups according to the applied workload (0.5 and 0.8 Watts/kg body mass) using a cycle ergometer and Cortex Metalyzer 3b equipment. The protocol was started with 6 minutes at constant load and then increments of 20-25 Watts every two min were made until determination of the peak VO2. The tau value was 51.8 ± 17.6 s, the absolute peak VO2 was 2.0 ± 0.7 L/min and the relative peak VO2 was 26.6 ± 30.0 ml/kg/min. There was a significant difference of tau medians between the group that used 0.5 and 0.8 Watts/kg (p = 0.002) and a significant inverse correlation between the absolute peak VO2 and the tau value for a load of 0.5 Watts/kg (rho = -0.415, p = 0.0327). The higher tau value, the lower the peak VO2 of an obese patient. It is suggested to apply loads of 0.5 Watts/kg for a VO2 kinetics test in obese patients or in subjects who do not wish to carry out higher physiological demands with a non-invasive and low risk procedure.

Study with a Portable Gas Analyzer of the 6-Minute Walk Test in Heart Failure with Normal Ejection Fraction

Abstract Background: Few studies have used portable gas analyzers during the 6-minute walk test (6MWT) in patients with heart failure and normal ejection fraction (HFNEF). Objectives: To analyze the kinetics of hemodynamic, ventilatory, and metabolic variables in patients with HFNEF during the T6m using a portable gas analyzer. Methods: Prospective, analytical study with an intentional, non-probabilistic, convenience sample. In total, 24 patients with HFNEF and past hospital admissions due to a clinical diagnosis of heart failure (HF) were included using the 2007 criteria established by the European Society of Cardiology. Three assessments were performed: 6MWT familiarization, 6MWT with the portable gas analyzer, and cardiopulmonary exercise test (CPET). Results: The heart rates (HRs) and the peak VO2 at the end of the 6MWT corresponded to 85.7% and 86.45% of the values obtained during the CPET. The final HRs after the T6m were equivalent to those obtained at the CPET anaerobic threshold (AT), with relative VO2 values at the end of the 6MWT above the VO2 of the CPET AT. There was no difference between the maximum respiratory quotient (RQ) values in these two tests, which were both above 1.0. The VE/VO2 slope descended initially and then ascended significantly after the fifth minute of the test, estimating the identification of the AT. Conclusions: In patients with HFNEF, the 6MWT represents an almost maximum effort, and is performed above the CPET AT and 85% above the maximum HR and the CPET peak VO2, with a maximum RQ similar to that in the CPET.

The Obesity Factor: How Cardiorespiratory Fitness is Estimated More Accurately in People with Obesity.

Cardiopulmonary exercise testing is clinically used to estimate cardiorespiratory fitness (CRF). The relation to total body mass (TBM) leads to an underestimation of CRF in people with obesity and to inappropriate prognostic and therapeutic decisions. This study aimed to determine body composition-derived bias in the estimation of CRF in people with obesity. Two hundred eleven participants (58.8% women; mean BMI 35.7 kg/m2 [± 6.94; 20.7-58.6]) were clinically examined, and body composition (InBody720; InBody Co., Ltd., Seoul, South Korea) and spiroergometrical peak oxygen consumption (VO2 peak) were assessed. The impacts of TBM, lean body mass (LBM), and skeletal muscle mass (SMM) on CRF estimates were analyzed by the application of respective weight models. Linear regression and plotting of residuals against BMI were performed on the whole study population and two subgroups (BMI < 30 kg/m2 and BMI ≥ 30 kg/m2 ). For every weight model, Δmean VO2 peak (expected - measured) was positive. LBM and SMM had a considerable impact on VO2 peak demand (P = 0.001; ΔR2 = 2.3%; adjusted R2 = 56% and P = 0.001; ΔR2 = 2.7%; adjusted R2 = 56%), whereas TBM did not. Confounding of body composition on VO2 peak did not differ in LBM and SMM. TBM-adjusted overestimation of relative VO2 demand is much higher in people with obesity than in those without. LBM or SMM adjustment may be superior alternatives, although small residual body composition-derived bias remains.

Cardiorespiratory responses during aquatic treadmill exercise and land treadmill exercise in older adults with type 2 diabetes.

The purpose of this study was to compare the effect of aquatic treadmill exercise (ATM) to land treadmill exercise (LTM) in adults with and without type 2 diabetes (T2D). Five participants with T2D (4 females, 1 male; age=51±3 years; height=170±3 cm; weight=96±11 kg; body fat=32±1%) and five participants without T2D (4 females, 1 male; age=51±3 years; height=170±3 cm; weight=71±15 kg; body fat=27±2%) completed the study. Participants completed three, 5-minute stages of exercise at 3.2 km/h, 4.8 km/h and 6.4 km/h with 0% grade on land and aquatic treadmills. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), absolute and relative oxygen consumption (VO2), and energy expenditure were measured at rest and during steady-state exercise at each intensity. A 2x2x4 Mixed Factorial ANOVA and Bonferroni post-hoc test with a significance level of 0.05 was used. All variables increased as speed increased (P<0.05) independent of group or mode. The HR value was higher on the LTM versus the ATM independent of group and treadmill stage (P=0.002) and SBP was higher in the T2D group versus no T2D independent of treadmill mode and stage (P=0.01). Relative VO2 was higher in the group without T2D compared to the T2D group at 6.4 km/h independent of treadmill mode (P=0.032). Although there is some evidence for the varying effects of aquatic and land exercise when comparing those with and without T2D, cardiorespiratory and metabolic variables are similar in both groups during locomotion on land and in an aquatic environment.

EXERCISE TRAINING-INDUCED CHANGES ON DNA METHYLATION IN MILD COGNITIVELY IMPAIRED OLDER AFRICAN AMERICANS: GEMS STUDY

DNA methylation at CpG sites is an important epigenetic modification of the human genome that can affect gene expression and potentially influence health outcomes. Notably, aging and physical exercise have been shown to influence epigenetic modification with during minimal exercise, inducing hypomethylation of the entire genome within muscle cells. However, there is paucity of data on exercise-induced training adaptation on DNA methylation in mild cognitively impaired (MCI) older African American (AA) undergoing well-characterized and supervised exercise intervention. Objective of Study: We explored the effects of a six-month aerobic and stretch exercise intervention on the epigenetic modifications and genome-wide DNA methylation of enrolled participants. Twenty-nine older AAs volunteers confirmed to be MCI, were randomly, assigned into a six-month program of either aerobic or stretch exercise. Participants underwent 40 minutes of supervised training 3 times/week. The maximal oxygen consumption (VO2Max) was determined at baseline and repeated after subjects completed the 6-month exercise program. Genome-wide methylation levels at CpG sites from 19 participants at baseline and a 6-month exercise training were profiled by using the Infinium HumanMethylation450 BeadChip assay. We examined the association between the change in CpG sites intensities and VO2 Max after 6 months of exercise adjusting for Age, APOE4 carrier status and randomization group. The participants averaged ∼71 years old in age, were 67.86% female and similar in mean relative VO2 Max (Stretch=24.72 (8.68) vs. Aerobic=22.74 (2.69); p = 0.715) at baseline. In total, we obtained DNA methylation data or 485,513 CpG sites from blood of 19 participants at baseline and after the exercise adaptation. Overall, six CpG sites demonstrated significant training-induced changes in methylation profile: p-values below 5 x 10-5 (cg06648780, cg06120404, cg08733824, cg14318197, cg26580761, cg24583624) with the first two CpG sites located on the ALCAM (leukocyte adhesion molecule) and C1orf88 (primary cilia formation) genes. We provide a genome-wide DNA methylation patterns associated with training-induced changes after a 6-month exercise adaptation. Whereas, efforts to understand the implications of these changes are ongoing, future studies should inform the relationships of changes in DNA methylation to mRNA expression in a predominantly AA sample, and correlate such changes with the MCI clinical phenotype.

Is respiratory exchange ratio an alternative to estimate anaerobic threshold in trained runners?

DOI: http://dx.doi.org/10.5007/1980-0037.2017v19n1p108 Several studies showed that respiratory exchange ratio (RER) have been used as an alternative to evaluate the aerobic capacity in a single incremental test. However, few studies have investigated trained runners. The aim of this study was to verify if the respiratory exchange ratio (RER) could be used as an alternative criterion for estimating anaerobic threshold (AT) in long-distance runners. Nineteen male long-distance runners volunteered to participate in the study. An incremental treadmill test was performed with initial speed of 10 km·h-1 with increments of 1 km·h-1 every 1 min until voluntary exhaustion. The variables measured were oxygen uptake (VO2), first and second ventilatory thresholds (VT1 and VT2, respectively), intensity corresponding to RER level of1.0 (iRER1.0), peak velocity (PV), heart rate (HR), and rate of perceived exertion (RPE). One-way repeated measure analysis variance was used, following Bonferroni post hoc test. Agreement between parameters was evaluated by Pearson correlation and dispersion error. There were no significant differences between iRER1.0 and VT2 parameters. The correlations were significant between iRER1.0 and VT2 parameters for absolute and relative VO2, speed, and HR (r=0.95; r=0.60; r=0.72; r=0.81, respectively). A small mean error (-0.2 km·h-1) was observed between iRER1.0 and VT2. However, it was also observed an overestimation trend for high speeds. In conclusion, iRER1.0 can be used as an alternative method to detect AT in long distance runners. However, its use is limited in runners with high aerobic capacity.

Patterning Of Physiological And Perceptual Responses To Exercise

The rating of perceived exertion (RPE), a subjective indicator of exercise intensity, is becoming increasingly popular for monitoring and prescribing exercise intensity in clinical populations. It remains unclear whether the relationship between RPE and oxygen uptake (VO2) is affected by perturbations to the sympathetic nervous system. PURPOSE: To determine whether acute sympathetic blockade alters the relationship between heart rate (HR), RPE and VO2 during incremental exercise. METHODS: Eleven healthy adults completed two graded exercise tests (GXT) on a motorized treadmill, under a β2 receptor antagonist and placebo. Treadmill speed increased by 2 km·h-1 every 2 min and participants reported their RPE (Borg 6-20 RPE Scale) each min until exhaustion. The VO2 and HR were measured continuously. Linear regression modelled the growth of individual participant relationships of RPE and HR with VO2. To account for differences in peak HR between conditions, values were expressed relative to the peak HR from each GXT. Paired sample t-tests assessed differences in the slope (b) of the individual regression models between conditions. RESULTS: The VO2peak and HRpeak were lower during β-blockade (51.9±5.3 vs 48.6±7.5 mL·kg-1·min-1, p<0.05; 192.7±8.2 vs 156.0±23.1 b·min-1, p<0.01, respectively). As expected, the slope for the relationship between HR and VO2 was greater during β-blockade (b 0.37±0.03 vs 0.48±0.07, p<0.01), however, there was no significant difference in the slope of the RPE:VO2 relationship (b 3.34±0.71 vs 3.30±0.77, respectively p>0.05) and no significant difference in b when HR was expressed relative to the peak HR during the GXT (b 0.71±0.07 vs 0.73±0.07, p>0.05). CONCLUSION: Despite a marginally lower VO2peak, the relationship between RPE and VO2 remains unchanged by sympathetic blockade, whereas the absolute HR:VO2 relationship is significantly altered. This means that RPE can be used in place of HR to determine metabolic work or estimate fitness sub-maximally in individuals taking β-blockade.

Comparison Of Cardiorespiratory Responses During Body Weight-supported Treadmill And Standard Treadmill Exercise

Treadmills that partially support body weight are used in some rehabilitation settings. Cardiorespiratory responses to this type of exercise have been reported in very few published studies. PURPOSE: To determine the cardiorespiratory response to graded exercise on a standard treadmill (ST) and body weight-supported treadmill (BWST). METHODS: In random order, 20-36 yr old adults (n = 6 males, 4 females) performed BWST and ST trials. Identical exercise sessions were performed on each treadmill except 25% of body weight was supported by the BWST. On each treadmill a two-minute warm up was performed at 2 mph and 0% grade, followed by 6 minutes of exercise at 3% grade at each of the following treadmill velocities: 3, 4.5, and 6 mph. Expired respiratory gases were analyzed each minute. Steady state heart rate, VO2, VCO2 and RER were calculated as the average value during the final three minutes of each 6 min exercise stage. Blood pressure and RPE were recorded during the final minute of each stage. A 2x3 repeated measures ANOVA was used to determine significant differences at the p<.05 level, and the LSD method for post hoc analyses. RESULTS: There was a significant difference (p<.05) in absolute VO2 between ST and BWST at 4.5 mph (2.14±.39 v 1.42±.27 l[BULLET OPERATOR]min-1) and 6 mph (2.75±.58 v 1.79±.40 l[BULLET OPERATOR]min-1). Relative VO2 was significantly different (p<.05) at each exercise intensity between treadmills (ST v BWST: 16.0±1.1 v 13.6±1.2; 31.2±2.0 v 20.6±2.4; 39.8±1.9 v 25.8±2.9 ml[BULLET OPERATOR]kg-1[BULLET OPERATOR]min-1). There was a significant difference (p<.05) in VCO2 between the ST and BWST at 4.5 mph (2.10±.43 v 1.32±.26 l[BULLET OPERATOR]min-1) and 6 mph (2.88±.63 v 1.68±.39 l[BULLET OPERATOR]min-1). There was a significant difference (p<.05) in RER between the ST (1.05±.08) and BWST (.94±.06) at 6 mph. The HR was significantly different (p<.05) between ST and BWST at 4.5 mph (162±17 v 128±17 bpm) and 6 mph (182±13 v 146±17 bpm). There was a significant increase (p<.05) in SBP on the ST (144±20 v 163±25 v 175±22 mmHg) and BWST (128±11 v 143±13 v 155±16 mmHg) at each exercise intensity. There were no significant differences in DBP at any point during exercise. There was a significant difference (p<.05) in RPE on the ST at 6 mph (15±1), 4.5 mph (12±1), and 3 mph (9±1). CONCLUSION: There appears to be a lower cardiorespiratory response during body weight-supported exercise and traditional treadmill exercise.

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.

Exercise Training Improves Ventilatory Efficiency in Patients With Small Abdominal Aortic Aneurysm

PURPOSE: To investigate the effects of exercise training on ventilatory efficiency and other physiological responses to submaximal exercise in subjects with small abdominal aortic aneurysm (AAA). METHODS: Sixty five patients (72.3±7.0 yr) were randomized to exercise training (n=33) or usual care groups (n=32). Exercise subjects participated in a training program for 3 months. Cardiopulmonary exercise testing was performed before and after the study period and peak VO2, the ventilatory threshold (VT), the oxygen uptake efficiency slope (OUES) and the VE/CO2 slope were identified. Baseline work rates at VT were matched to examine cardiopulmonary responses before and after training. ANOVA was used to assess time by group interactions. RESULTS: Significant interactions indicating improvements in the exercise group were observed for time (p<0.01), VO2 (p<0.01), and work rate (p<0.01) at the VT. At peak effort, significant interactions were noted for time (p<0.01) and work rate (p<0.01), while borderline significance was noted for absolute (p=0.07) and relative (p=0.04) VO2. Significant interactions were observed for the OUES both when using all exercise test data (Exercise: 2.03 to 2.16, and Usual care: 2.10 to 1.98; p for interaction =0.04) and when calculated up to the VT (Exercise: 2.07 to 2.23, and Usual care: 2.13 to 1.95; p for interaction <0.01). For the VE/VCO2 slope, significance was only noted when calculated up to the VT (Exercise: 30.4 to 29.5, and Usual care: 29.2 to 30.3; p for interaction=0.04). After training, heart rate (104.5 to 97.3 bpm), VE (34.2 to 32.0 L/min), VCO2 (1013.6 to 910.6 ml/min) and respiratory exchange ratio (0.85 to 0.82) were significantly attenuated for the same baseline workrate in the exercise group (all p<0.01), but no changes were observed in the usual care group. CONCLUSIONS: Exercise training improves ventilatory efficiency in patients with small AAA. In addition, exercised patients exhibited less demanding cardiorespiratory responses to submaximal effort, with potential clinical significance for activities of daily living.

Muscle Deoxygenation during Incremental Exercise is Delayed in Children Compared to Young Adults

The mechanisms regulating O2 delivery and utilization during endurance exercise differ with maturation and are incompletely understood. This is important to understand the development of cardiovascular and neuromuscular diseases that originate early in life. Time-resolved near-infrared spectroscopy (TRS-NIRS) provides a quantitative non-invasive measurement of deoxy- hemoglobin + myoglobin concentration ([HHb]) at the muscle, an indicator of muscle deoxygenation during exercise. PURPOSE: To compare [HHb] dynamics during incremental ramp exercise in healthy early pubertal children and young adults. METHODS: 23 early pubertal children (16 F; 7-11 years) and 15 young adults (7 F; 21-35 years) underwent an incremental ramp exercise test on a cycle ergometer. Pulmonary gas exchange was measured breath-by-breath (Vmax, Carefusion). Vastus lateralis [HHb] was quantified by TRS-NIRS (TRS-21, Hamamatsu Photonics). RESULTS: Peak VO2 was not different between children and adults normalized to body mass (46.7±8.1 vs. 48.9±7.7 mL/min/kg). Absolute [HHb] was not different between children and adults during unloaded pedaling (23.5±5.5 vs 26.8±10.0 uM, p=0.20) but adults had a higher peak exercise [HHb] (32.0±8.2 vs 44.4±22.6 uM, p=0.01). Two way RM-ANOVA of relative HHb dynamics revealed an effect of age (F(1,36) = 6.895, p=0.013) and interaction with % peak power (p=0.001, Figure). Post-hoc, relative HHb was lower at 60% peak power in children vs adults (57±10% vs 68±13%, p=0.0006), while VO2 did not differ (33.5±4.9% vs 30.6±6.2%, p=0.12). CONCLUSION: Muscle deoxygenation is both attenuated and delayed during incremental exercise in children compared to adults, despite similar relative VO2. This is consistent with a closer matching of muscle microvascular O2 delivery to utilization over a greater range of aerobic power in children. The mechanisms contributing to this improved regulation of muscle blood flow during exercise in children warrant further study.Figure

Effects of Bodyweight Exercise on Excess Post-exercise Oxygen Consumption and Metabolic Expenditure

INTRODUCTION: Body weight exercises (BWE; push-ups, squats, lunges) are popular modes of exercise, yet little is known regarding their effects on caloric expenditure. Classic hypertrophy training results in up to four-hour excess post-exercise oxygen consumption (EPOC) and elevated 24-hour resting metabolic rate (RMR). The purpose of this study was to determine if BWE 1) alters the length and amount of EPOC and 2) increases 24-hour RMR. METHODS: Four healthy adult volunteers (3 males, 1 female; age:22±2y, height:168±11 cm, mass:74.7±18.6 kg, body fat:27.8±4.7%) consumed standard diets and underwent two RMR measures [pre- (morning) and post- (following morning) BWE]. Three hours following pre-RMR, participants completed a BWE bout [4 sets of push-ups (~9 reps), squats (~14 reps), and lunges (~14 reps)], followed by a 4 hour EPOC test. To standardize the work done participants performed 1-repetition maximum tests for bench-press and leg-press (to determine number of repetitions for BWE). RESULTS: It was found that a bout of BWE elevated relative VO2 (rVO2; ml/kg/min) and energy expenditure post-exercise. When comparing pre-RMR to EPOC there was a significant difference at minute 15 in both rVO2 (p<0.02) and caloric expenditure (p<0.05). Yet, there was no significant difference in both rVO2 and caloric expenditure when pre-RMR and post-RMR were compared. CONCLUSIONS: As expected, we found that EPOC occurs after BWE, but is only elevated up to 30 minutes after exercise. This shows that BWE is an efficient and practical way to elevate metabolic rate, leading to increased caloric expenditure while potentially saving time and money. More participants are needed to fully understand the physiological implications of BWE related to caloric expenditure in healthy adults.

Is There an Oxygen Pulse Threshold During Treadmill Running?

It has been suggested there are two separate breakpoints in the oxygen pulse (O2 pulse = VO2/heart rate) versus workload relationship during incremental cycle ergometry, corresponding to the first and second turn points in the blood lactate response. It is still unclear if these O2 pulse breakpoints can be detected during treadmill running, and if detected, where these thresholds may be located relative to the gas exchange threshold (GET) and respiratory compensation point (RCP). PURPOSE: This study examined the relationship between O2 pulse and exercise intensity to determine if O2 pulse thresholds could be detected during treadmill running, and, if detected, to compare these O2 pulse thresholds to the GET and RCP. METHODS: Twelve, moderately trained runners (6 men and 6 women; age = 23 ± 3 years; height = 175 ± 8 cm; weight = 71 ± 12 kg) completed an incremental treadmill test to exhaustion for the measurement of gas exchange, ventilation, and heart rate parameters, as well as the determination of VO2 peak. The GET and RCP were determined from the breakpoint in the VCO2 versus VO2 and VE versus VCO2 relationships, respectively. The O2 pulse was plotted against VO2 for each subject and the relationship between these two variables was examined using polynomial regression models (linear and quadratic) at an alpha level of p ≤ 0.05. RESULTS: The mean (± SD) VO2 peak was 3.475 ± 0.959 L·min-1 (48.33 ± 7.30 mL·kg-1·min-1). The GET (2.289 ± 0.617 L·min-1) and RCP (3.029 ± 0.867 L·min-1) occurred at 67 ± 5% and 88 ± 4 % of VO2 peak, respectively. The O2 pulse versus VO2 relationship was best explained by a linear fit (r2 = 0.976 - 1.000) for 9 and a quadratic fit (R2 = 0.985 - 0.996) for 3 of the 12 subjects. Only 1 of the 3 subjects with a quadratic fit for the O2 pulse versus VO2 relationship displayed a response consistent with a plateau in the O2 pulse. CONCLUSIONS: The highly linear relationship between O2 pulse and VO2 for 75% of the subjects indicated that O2 pulse thresholds could not be detected during treadmill running using the O2 pulse versus VO2 relationship. These findings do not support the use of the O2 pulse as a non-invasive measure of fatigue thresholds.