Ramp-incremental Cycle Ergometry Research Articles

Critical Power and Respiratory Compensation Point Are Not Equivalent in Patients with COPD.

Several studies report that pulmonary oxygen uptake (V̇O 2 ) at the respiratory compensation point (RCP) is equivalent to the V̇O 2 at critical power (CP), suggesting that the variables can be used interchangeably to demarcate the threshold between heavy and severe intensity domains. However, if RCP is a valid surrogate for CP, their values should correspond even when assessed in patients with chronic obstructive pulmonary disease (COPD) in whom the "normal" mechanisms linking CP and RCP are impeded. The aim of this study was to compare V̇O 2 at CP with V̇O 2 at RCP in patients with COPD. Twenty-two COPD patients (14 male/8 female; forced expiratory volume in 1 s, 46% ± 17% pred) performed ramp-incremental cycle ergometry to intolerance (5-10 W·min -1 ) for the determination of gas exchange threshold (GET) and RCP. CP was calculated from the asymptote of the hyperbolic power-duration relationship from 3-5 constant-power exercise tests to intolerance. CP was validated with a 20-min constant-power ride. GET was identified in 20 of 22 patients at a V̇O 2 of 0.93 ± 0.18 L·min -1 (75% ± 13% V̇O 2peak ), whereas RCP was identified in just 3 of 22 patients at a V̇O 2 of 1.40 ± 0.39 L·min -1 (85% ± 2% V̇O 2peak ). All patients completed constant-power trials with no difference in peak physiological responses relative to ramp-incremental exercise ( P > 0.05). CP was 46 ± 22 W, which elicited a V̇O 2 of 1.04 ± 0.29 L·min -1 (90% ± 9% V̇O 2peak ) during the validation ride. The difference in V̇O 2 at 15 and 20 min of the validation ride was 0.00 ± 0.04 L, which was not different from a hypothesized mean of 0 ( P = 0.856), thereby indicating a V̇O 2 steady state. In COPD patients, who present with cardiopulmonary and/or respiratory-mechanical dysfunction, CP can be determined in the absence of RCP. Accordingly, CP and RCP are not equivalent in this group.

High Pulse Pressure Decreases Cardiopulmonary Ability among Older Chinese Patients with Primary Hypertension.

There is limited information regarding the reference values for cardiopulmonary exercise testing (CPX) variables in patients with primary hypertension. Our aim was to provide such values. In this single-center, retrospective study, we included 635 patients (male, 53.7%; mean ± standard deviation age, 62.1 ± 12.6 years) who completed maximal ramp incremental CPX using cycle ergometry at the Rui An Hospital of Traditional Chinese Medicine from August 1, 2018, to December 31, 2021. The patients were classified into two groups based on pulse pressure (PP): (1) patients with a low PP ≤ 60 mmHg (n = 324) and (2) patients with a high PP > 60 mmHg (n = 311). Stepwise linear regression was used to fit the equations of the key CPX variables. CPX was self-interrupted owing to fatigue by 64.5% (low PP) and 72.0% (high PP) of patients (χ2 analysis, P = 0.05). The anaerobic threshold (AT) could not be determined in 3.7% and 7.7%, respectively (χ2 analysis, P = 0.038). Peak oxygen consumption (VO2), carbon dioxide production, ventilation/minute, work rate, and VO2 at the AT were associated with age, weight, and sex. Moreover, a high PP was associated with impaired anaerobic exercise ability, as indicated by the reduced peak VO2, peak VE, and absolute peak work rate. Compared with prior research of a healthy population, patients with primary hypertension in this study exhibited impaired cardiopulmonary ability both at rest and during exercise, especially in the high PP group. The reference values and predictive equations for CPX variables provide a framework for interpreting the response to maximal ramp incremental cycle ergometry among older Chinese patients with primary hypertension.

A Comparison Of Critical Power And Respiratory Compensation Point In COPD: Coincidence Or Equivalence?

Power output at the respiratory compensation point (RCP), measured as the breakpoint in the linear ventilation-carbon dioxide output (V̇E-V̇CO2) relationship during ramp-incremental exercise, is proposed to be equivalent to critical power (CP): the asymptote of the hyperbolic power-duration relationship (P-tLIM). For RCP to be used as a valid index of CP, their values should remain equivalent, even under pulmonary mechanical constraint (e.g., in patients with chronic obstructive pulmonary disease [COPD]). PURPOSE: To determine power output (W) and oxygen uptake (V̇O2) at RCP and CP measured using gold-standard protocols in patients with COPD. METHODS: Ten COPD patients (4 female) volunteered (FEV1 = 41 ± 16% predicted). Power output and V̇O2 at gas exchange threshold (GET) and RCP were measured during ramp-incremental cycle ergometry (5-10 W/min). Critical power was estimated from the asymptote of the hyperbolic P-tLIM relationship from 3-4 constant power exercise tests. Oxygen uptake was measured at 15 and 20 min of a constant power ride at CP. RESULTS: Gas exchange threshold was observed in 9/10 patients and occurred at a V̇O2 of 0.91 ± 0.19 L/min (71 ± 28% V̇O2peak). Respiratory compensation point was identified in 1/10 patients and occurred at a V̇O2 of 1.57 L/min (87% V̇O2peak) versus 1.45 L/min at CP (90 W vs. 67 W, respectively). At intolerance, group mean V̇O2peak was 1.15 ± 0.34 L/min and V̇Epeak was 42.7 ± 20.0 L/min (90 ± 15% of estimated MVV). Ramp-incremental V̇O2peak was not different to that obtained in the 3-4 tests used to characterize the P-tLIM relationship (p = 0.419) and with no differences among tests (p = 0.102; mean V̇O2peak = 1.17 ± 0.32 L/min). Critical power was 37 ± 17 W. In the 9/10 patients who completed the 20 min CP validation ride, V̇O2 reached a steady-state (no difference in values at 15 vs. 20 min; p = 0.47) and was calculated as 1.02 ± 0.27 L/min (90 ± 7 % of ramp-incremental V̇O2peak). CONCLUSIONS: CP was identified in all COPD patients, and the steady-state V̇O2 at CP was sub-maximal. The absence of RCP in 9/10 patients, despite exercise gas-exchange responses consistent with a metabolic acidosis, shows that RCP and CP do not occur at equivalent power output or V̇O2 under conditions of abnormal metabolic, respiratory, and/or ventilatory function. RCP should not be used as a valid surrogate for CP.

Characteristics and reference values for cardiopulmonary exercise testing in the adult Chinese population – The Xiangya hospital exercise testing project (the X-ET project)

BackgroundReference values of cardiopulmonary exercise testing (CPX) vary with race/ethnicity. Chinese Americans are the fastest-growing racial/ethnic group in the United States. However, there is limited information about the reference values of cardiopulmonary exercise testing (CPX) variables in the Chinese population. MethodsAs part of the Xiangya Hospital Exercise Testing project (the X-ET project), this cross-sectional study screened 20,696 consecutive CPXs performed by 17,802 unique individuals at Xiangya Hospital of Central South University, China, from January 1, 2002, to December 31, 2019. A total of 964 unique healthy adults/tests (42% female) aged 49 ± 12 who completed a maximal ramp incremental CPX with cycle ergometry were included in this study. The reference values of primary CPX variables were expressed as the lower limit or upper limit of normal. Stepwise linear regression was used to fit the equations of key CPX variables. Predictive accuracy analysis for the equations with a comparison between present and previous studies were performed. ResultsPeak oxygen consumption (V̇O2), carbon dioxide production, ventilation/min, work rate, and V̇O2 at the anaerobic threshold were regressed on age, height, weight, and sex. These predictive equations showed good in- and out-sample predictive accuracy. Comparison with prior research revealed that prediction equations of peak V̇O2 resultant from studies in which populations were entirely or primarily Caucasian had overestimated our subjects' actual values. ConclusionThe reference values and predicted equations of CPX variables in this study may provide a more appropriate framework to interpret the response to maximal ramp incremental cycle ergometry in the Chinese adult population.

A practical approach to assess leg muscle oxygenation during ramp-incremental cycle ergometry in heart failure.

Heart failure is characterized by the inability of the cardiovascular system to maintain oxygen (O2) delivery (i.e., muscle blood flow in non-hypoxemic patients) to meet O2 demands. The resulting increase in fractional O2 extraction can be non-invasively tracked by deoxygenated hemoglobin concentration (deoxi-Hb) as measured by near-infrared spectroscopy (NIRS). We aimed to establish a simplified approach to extract deoxi-Hb-based indices of impaired muscle O2 delivery during rapidly-incrementing exercise in heart failure. We continuously probed the right vastus lateralis muscle with continuous-wave NIRS during a ramp-incremental cardiopulmonary exercise test in 10 patients (left ventricular ejection fraction <35%) and 10 age-matched healthy males. Deoxi-Hb is reported as % of total response (onset to peak exercise) in relation to work rate. Patients showed lower maximum exercise capacity and O2 uptake-work rate than controls (P<0.05). The deoxi-Hb response profile as a function of work rate was S-shaped in all subjects, i.e., it presented three distinct phases. Increased muscle deoxygenation in patients compared to controls was demonstrated by: i) a steeper mid-exercise deoxi-Hb-work rate slope (2.2±1.3 vs 1.0±0.3% peak/W, respectively; P<0.05), and ii) late-exercise increase in deoxi-Hb, which contrasted with stable or decreasing deoxi-Hb in all controls. Steeper deoxi-Hb-work rate slope was associated with lower peak work rate in patients (r=–0.73; P=0.01). This simplified approach to deoxi-Hb interpretation might prove useful in clinical settings to quantify impairments in O2 delivery by NIRS during ramp-incremental exercise in individual heart failure patients.

Power-Velocity and Power-Efficiency Implications in the Limitation of Ramp Incremental Cycle Ergometry: Reply to Morales-Alamo et al.

to the editor: We thank Morales-Alamo et al. ([5][1]) for raising important questions worthy of further discussion. A key concern of both our studies ([3][2], [4][3]) is whether the limit of tolerance (LoT) in ramp-incremental exercise is reached with a reserve in power producing capacity. To this

Exercise oxygen uptake efficiency slope independently predicts poor outcome in pulmonary arterial hypertension

To the Editor: Pulmonary arterial hypertension (PAH) remains a disabling and frequently lethal disease despite remarkable advances in treatment. Cardiopulmonary exercise testing (CPET) has proved a valuable tool to objectively quantify disease severity and estimate prognosis in these patients [1–3]. Exercise intolerance is characteristically multifactorial in PAH. Among its potential contributing mechanisms, increased ventilatory response, deranged pulmonary mechanics, peripheral muscle impairment and reduced oxygen delivery have been more widely investigated [1–5]. In this context, a CPET-derived variable that conflates the effects of increased ventilation and poor O2 transfer and/or peripheral O2 utilisation is the O2 uptake efficiency slope (OUES) [6]. OUES is the slope of the linear relationship between O2 uptake ( V ′O2) and the logarithmic transformation of minute ventilation ( V ′E) during rapidly incremental exercise, i.e. it aims to reflect how effectively O2 is extracted from the atmosphere and taken into the body as exercise progresses. We recently found that a combination of increased sub-maximal exercise V ′E as a function of carbon dioxide output ( V ′CO2) and reduced O2 delivery/utilisation (as suggested by shallow V ′O2–work rate relationship) were independent predictors of negative outcome in PAH of mixed aetiology [7]. These findings prompted the hypothesis that OUES would combine the prognostic information provided separately by those variables, thereby being the single predictor of poor outcome in our cohort. In order to address this question, we revisited our dataset and contrasted OUES prognostic relevance with that of a range of resting and cardiopulmonary exercise responses to ramp-incremental cycle ergometry. In the previous report [7], we described results from a group of 84 patients in whom 16 PAH-related deaths and two …

Acute BDNF and cortisol response to low intensity exercise and following ramp incremental exercise to exhaustion in humans

The effect of short-term aerobic exercise and a following ramp incremental cycle ergometry to exhaustion on the acute response of the serum concentrations of brain derived neurotrophic factor (BDNF) and cortisol (COR) was examined in 8 healthy male athletes. Venous and capillary blood samples were drawn at rest, immediately after a 10 min warm-up period with aerobic exercise and after a ramp test to exhaustion, as well as 3, 6, 10 and 15 min post exercise. Capillary blood lactate (LA) concentration and blood gases as well as serum BDNF and COR concentrations did not change during the warm-up period. LA was increased ( p < 0.05) at the end of the ramp test and during recovery period while bicarbonate concentration, carbon dioxide pressure, pH and base excess were decreased ( p < 0.05) during this period. Serum BDNF was increased at the point of exhaustion ( p < 0.05) while no significant differences were found between values at rest and those during recovery period. At 10 and 15 min post incremental exercise, COR concentrations were increased ( p < 0.05) compared to rest. The present study is the first to demonstrate in humans that in contrast to short duration aerobic exercise immediately after a following short duration high-intensity exercise to exhaustion, there is a transient augmentation of serum BDNF concentration. Short-term response of serum BDNF and COR concentrations differs as BDNF returns to baseline level faster than COR.

A Simplified Strategy for the Estimation of the Exercise Ventilatory Thresholds

To analyze the limits of agreement between exercise ventilatory threshold values (VT1 and VT2) estimated from a combination of pulmonary gas exchange and ventilatory variables (cardiopulmonary exercise testing) and those derived from an alternative approach based on the ventilatory response only (V(E), ventilometry). Forty-two nontrained subjects (24 males, aged 18-48, peak VO(2) = 33.1 +/- 8.6 mL.min(-1).kg(-1)) performed a maximum incremental cardiopulmonary exercise testing on an electromagnetically braked cycle ergometer. The participants breathed through a Pitot tube (Cardio2 System, MGC) and a fixed-resistance ventilometer (Micromed, Brazil), which were connected in series. HR values at the estimated VT (VTHR1 and VTHR2) were obtained by the conventional method (ventilatory equivalents, end-expiratory pressures for O(2) and CO(2), and the V-slope procedure) and an experimental approach (V(E) vs time, V(E)/time vs time, and breathing frequency vs time). There were no significant between-method differences on VT(HR1), VT(HR2), VT(VE1), VT(VE2), and peak V(E) (P > 0.05). After certification of data normality, a Bland-Altman analysis revealed that the mean bias +/- 95% confidence interval of the between-method differences were lower for VT(HR2) than VT(HR1) (2 +/- 9 and 0 +/- 17 bpm, respectively). VT(HR2) according to ventilometry differed more than 10 bpm from the standard procedure in 3 out of 42 subjects (9%). Between-method differences were independent of the level of fitness, as estimated from peak VO(2) (P > 0.05). : A simplified approach, based on the ventilatory response as a function of time, can provide acceptable estimates of the exercise ventilatory thresholds--especially VT2--during ramp-incremental cycle ergometry. This new strategy might prove to be useful for exercise training prescription in nontrained adults.

Non-linear cardiac output dynamics during ramp-incremental cycle ergometry

Published literature asserts that cardiac output (Q(.) = V(.) >O(2)x1/C((a-v))O(2)) increases as a linear function of oxygen uptake with a slope of approximately 5-6 during constant work rate exercise. However, we have previously demonstrated that C((a-v))O(2) has a linear relationship as a function of V(.)O(2) during progressively increasing work rate incremental exercise. Therefore, we hypothesized that Q(.) may indeed have a non-linear relationship with respect to V(.)O(2) during incremental, non-steady state exercise. To investigate this hypothesis, we performed five maximal progressive work rate exercise studies in healthy human subjects. Q(.) was determined every minute during exercise using measured breath-by-breath V(.) >O(2), and arterial and pulmonary artery measurements of PO(2), hemoglobin saturation, and content. Q(.) was plotted as a function of V(.) >O(2) and the linear and non-linear (first order exponential and hyperbolic) fits determined for each subject. Tests for linearity were performed by assessing the significance of the quadratic terms added to the linear relation using least squares estimation in linear regression. Linearity was inadequate in all cases (group P<0.0001). We conclude that cardiac output is a non-linear function of V(.)O(2 )during ramp-incremental exercise; the pattern of non-linearity suggests that while the kinetics of Q(.) > are faster than those of V(.) >O(2) they progressively slow as work rate (and V(.) >O(2)) increases.

Influence of exercise intensity on the on- and off-transient kinetics of pulmonary oxygen uptake in humans.

1. The maximal oxygen uptake (V(O(2),peak)) during dynamic muscular exercise is commonly taken as a crucial determinant of the ability to sustain high-intensity exercise. Considerably less attention, however, has been given to the rate at which V(O(2)) increases to attain this maximum (or to its submaximal requirement), and even less to the kinetic features of the response following exercise. 2. Six, healthy, male volunteers (aged 22 to 58 years), each performed 13 exercise tests: initial ramp-incremental cycle ergometry to the limit of tolerance and subsequently, on different days, three bouts of square-wave exercise each at moderate, heavy, very heavy and severe intensities. Pulmonary gas exchange variables were determined breath by breath throughout exercise and recovery from the continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). 3. For moderate exercise, the V(O(2)) kinetics were well described by a simple mono-exponential function, following a short cardiodynamic phase, with the on- and off-transients having similar time constants (tau(1)); i.e. tau(1,on) averaged 33 +/- 16 s (+/- S.D.) and tau(1,off) 29 +/- 6 s. 4. The on-transient V(O(2)) kinetics were more complex for heavy exercise. The inclusion of a second slow and delayed exponential component provided an adequate description of the response; i.e. tau(1,on) = 32 +/- 17 s and tau(2,on) = 170 +/- 49 s. The off-transient V(O(2)) kinetics, however, remained mono-exponential (tau(1,off) = 42 +/- 11 s). 5. For very heavy exercise, the on-transient V(O(2)) kinetics were also well described by a double exponential function (tau(1,on) = 34 +/- 11 s and tau(2,on) = 163 +/- 46 s). However, a double exponential, with no delay, was required to characterise the off-transient kinetics (i.e. tau(1,off) = 33 +/- 5 s and tau(2,off) = 460 +/- 123 s). 6. At the highest intensity (severe), the on-transient V(O(2)) kinetics reverted to a mono-exponential profile (tau(1,on) = 34 +/- 7 s), while the off-transient kinetics retained a two-component form (tau(1,off) = 35 +/- 11 s and tau(2,off) = 539 +/- 379 s). 7. We therefore conclude that the kinetics of V(O(2)) during dynamic muscular exercise are strikingly influenced by the exercise intensity, both with respect to model order and to dynamic asymmetries between the on- and off-transient responses.