Incremental Work Rate Research Articles

EPS1.01 Predicting ‘optimal’ work rate increments for cycle ergometry tests in cystic fibrosis

EPS1.01 Predicting ‘optimal’ work rate increments for cycle ergometry tests in cystic fibrosis

Evaluation of Surgical N95 Respirators Covered With Combinations of Masks and Face Shield.

The aim of the study is to evaluate the metabolic demands and internal breathing environments when covering an N95 with a surgical mask, cloth mask, and/or FS. Three N95 models approved by the National Institute for Occupational Safety and Health were evaluated under six covering conditions using the National Institute for Occupational Safety and Health Automated Breathing and Metabolic Simulator. All conditions used one trial with each N95 for six incremental 5-minute work rates. Inhaled oxygen and carbon dioxide concentrations, peak inhaled and exhaled pressures, and inhaled wet-bulb and dry-bulb temperatures were measured continuously and averaged across all work rates and covering conditions. Results suggest that metabolic demands and internal breathing environments are significantly impacted by all combinations of coverings tested when compared to N95 only.

Steep ramp test protocol for preoperative risk assessment and short-term high-intensity interval training to evaluate, improve, and monitor cardiorespiratory fitness in surgical oncology.

Steep ramp test protocol for preoperative risk assessment and short-term high-intensity interval training to evaluate, improve, and monitor cardiorespiratory fitness in surgical oncology.

Efficacy of 12weeks oral beta-alanine supplementation in patients with chronic obstructive pulmonary disease: a double-blind, randomized, placebo-controlled trial.

BackgroundBeta‐alanine (BA) supplementation increases muscle carnosine, an abundant endogenous antioxidant and pH buffer in skeletal muscle. Carnosine loading promotes exercise capacity in healthy older adults. As patients with chronic obstructive pulmonary disease (COPD) suffer from elevated exercise‐induced muscle oxidative/carbonyl stress and acidosis, and from reduced muscle carnosine stores, it was investigated whether BA supplementation augments muscle carnosine and induces beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress in patients with COPD.MethodsIn this double‐blind, randomized, placebo (PL)‐controlled trial (clinicaltrials.gov identifier: NCT02770417), 40 patients (75% male) with COPD (mean ± standard deviation: age 65 ± 6 years; FEV1% predicted 55 ± 14%) were assigned to 12 weeks oral BA or PL supplementation (3.2 g/day). The primary outcome, i.e. muscle carnosine, was quantified from m. vastus lateralis biopsies obtained before and after intervention. Co‐primary outcomes, i.e. incremental and constant work rate cycle capacity, were also assessed. Linear mixed model analyses were performed. Compliance with and side effects of supplement intake and secondary outcomes (quadriceps strength and endurance, and muscle oxidative/carbonyl stress) were also assessed.ResultsBeta‐alanine supplementation increased muscle carnosine in comparison with PL in patients with COPD (mean difference [95% confidence interval]; +2.82 [1.49–4.14] mmol/kg wet weight; P < 0.001). Maximal incremental cycling capacity (VO2peak: +0.5 [−0.7 to 1.7] mL/kg/min; P = 0.384, Wpeak: +5 [−1 to 11] W; P = 0.103) and time to exhaustion on the constant work rate cycle test (+28 [−179 to 236] s; P = 0.782) did not change significantly. Compliance with supplement intake was similar in BA (median (quartile 1–quartile 3); 100 (98–100)%) and PL (98 (96–100)%) (P = 0.294) groups, and patients did not report side effects possibly related to supplement intake. No change was observed in secondary outcomes.ConclusionsBeta‐alanine supplementation is efficacious in augmenting muscle carnosine (+54% from mean baseline value) without side effects in patients with COPD in comparison with PL. However, accompanied beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress were not observed.

A NIRS‐derived Skeletal Muscle Oxygen Consumption Method Accurately Reflects the Gold Standard Direct Fick Method during Single‐leg Knee Extension Exercise

BackgroundQuantifying the oxygen consumption (V̇O2) of skeletal muscle, which represents the largest metabolically‐active tissue mass, is an important assessment in exercise physiology. The gold standard for quantifying muscle V̇O2 in the exercising human is the direct Fick method, however, technical challenges (e.g. arterial catheter insertion) preclude the widespread use of this technique, justifying the need for alternative approaches for the quantification of muscle V̇O2. Recently, we developed a noninvasive method of quantifying muscle V̇O2 using Doppler ultrasound measurements of blood flow (Q̇) and near‐infrared spectroscopy (NIRS)‐derived deoxygenated‐[Heme] in a modified Fick method calculation, but, to date, this has not been validated against the gold standard method.Purpose and HypothesesTherefore, the purpose of this investigation was to compare NIRS‐derived and direct Fick quantification of muscle V̇O2 at multiple levels of single‐leg knee‐extensor exercise. We tested the hypotheses that: 1) the muscle V̇O2 assessed by direct Fick and the NIRS‐derived muscle V̇O2 would not be statistically different from each other across work rates, and 2) the V̇O2 assessed by the two techniques would be strongly related.MethodsSeven healthy young volunteers (3 women, 4 men; 24 ± 5 years) performed an incremental work rate test on a dynamic single‐leg knee‐extensor ergometer. Measurements of femoral artery Q̇ (Doppler ultrasound), vastus lateralis deoxygenated‐[Heme] (NIRS), and femoral artery and vein oxygen content were taken at rest, 0, 5, 10, 15, and 20 Watts (W) and used to estimate direct Fick and NIRS‐derived muscle V̇O­2.ResultsNIRS‐derived V̇O2 was not different from direct Fick V̇O2 at any point (rest: 45 ± 21 vs 25 ± 17 ml/min; 0 W: 153 ± 70 vs 133 ± 68 ml/min; 5 W: 188 ± 81 vs 160 ± 65 ml/min; 10 W: 242 ± 123 vs 214 ± 91 ml/min; 15 W: 279 ± 131 vs 247 ± 89 ml/min; 20 W: 343 ± 163 vs 319 ± 122 ml/min; all P = 0.26 – 0.44). Muscle V̇O2determined by the two techniques was strongly related (r2: 0.97 ± 0.03) with a slope of 1.1 ± 0.3 and Y‐intercept of ‐21 ± 22 ml/min.DiscussionTaken together, these findings indicate that the NIRS‐derived, noninvasive assessment of skeletal muscle V̇O2 accurately reflects the gold standard quantification of muscle V̇O2over a range of work rates (with a constant ≍20 ml/min offset). This investigation provides the first evidence to support the use of the NIRS‐derived muscle V̇O2 estimate during free‐flow conditions (i.e. not using venous or arterial occlusions like previous work), introducing a novel, noninvasive technique to quantify exercising skeletal muscle V̇O2.

Energy expenditure during cardiopulmonary exercise testing

Objectives: To determine energy expenditure during cardiopulmonary exercise testing in healthy adults aged 20-60 years old and to determine the correlation between energy expenditure with the duration and the capacity of physical activity. Methods: Thirty-two healthy volunteers aged 20-60 years old (17 males and 15 females) agreed to participate in our study and performed cardiopulmonary exercise testing: resting phase (4 minutes, work rate 0 w), warming-up phase (4 minutes, work rate 0 w, 50-60 rounds per minute), exercise phase (work rate increment 10 watts per minutes, 50-60 rounds per minute) and recovery phase (3 minutes, work rate 0 w, 10-20 rounds per minute). Results and conclusions: Energy expenditure during CPET was 1,03 ± 0,30 MET, 1,97 ± 0,74 MET, 3,48 ± 1,78 MET, 4,57 ± 2,26 in resting, warming-up, exercise, recovery phase, respectively. Maximum energy expenditure during CPET was 4,75 ± 2,17 MET. Energy expenditure is negatively correlated with the duration of physical activity and positively correlated with the capacity of physical activity at 95% confidence interval.

Cardiorespiratory kinetics in exercise physiology: estimates and predictions using randomized changes in work rate

PurposeKinetics of cardiorespiratory parameters (CRP) in response to work rate (WR) changes are evaluated by pseudo-random binary sequences (PRBS testing). In this study, two algorithms were applied to convert responses from PRBS testing into appropriate impulse responses to predict steady states values and responses to incremental increases in exercise intensity.Methods13 individuals (age: 41 ± 9 years, BMI: 23.8 ± 3.7 kg m−2), completing an exercise test protocol, comprising a section of randomized changes of 30 W and 80 W (PRBS), two phases of constant WR at 30 W and 80 W and incremental WR until subjective fatigue, were included in the analysis. Ventilation (dot{V}_{{text{E}}}), O2 uptake (dot{V}{text{O}}_{2}), CO2 output (dot{V}{text{CO}}_{2}) and heart rate (HR) were monitored. Impulse responses were calculated in the time domain and in the frequency domain from the cross-correlations of WR and the respective CRP.ResultsThe algorithm in the time domain allows better prediction for dot{V}{text{O}}_{2} and dot{V}{text{CO}}_{2}, whereas for dot{V}_{{text{E}}} and HR the results were similar for both algorithms. Best predictions were found for dot{V}{text{O}}_{2} and HR with higher (3–4%) 30 W steady states and lower (1–4%) values for 80 W. Tendencies were found in the residuals between predicted and measured data.ConclusionThe CRP kinetics, resulting from PRBS testing, are qualified to assess steady states within the applied WR range. Below the ventilatory threshold, dot{V}{text{O}}_{2} and HR responses to incrementally increasing exercise intensities can be sufficiently predicted.

Energy expenditure during cardiopulmonary exercise testing

Objectives: To determine energy expenditure during cardiopulmonary exercise testing in healthy adults aged 20-60 years old and to determine the correlation between energy expenditure with the duration and the capacity of physical activity. Methods: Thirty-two healthy volunteers aged 20-60 years old (17 males and 15 females) agreed to participate in our study and performed cardiopulmonary exercise testing: resting phase (4 minutes, work rate 0 w), warming-up phase (4 minutes, work rate 0 w, 50-60 rounds per minute), exercise phase (work rate increment 10 watts per minutes, 50-60 rounds per minute) and recovery phase (3 minutes, work rate 0 w, 10-20 rounds per minute). Results and conclusions: Energy expenditure during CPET was 1,03 ± 0,30 MET, 1,97 ± 0,74 MET, 3,48 ± 1,78 MET, 4,57 ± 2,26 in resting, warming-up, exercise, recovery phase, respectively. Maximum energy expenditure during CPET was 4,75 ± 2,17 MET. Energy expenditure is negatively correlated with the duration of physical activity and positively correlated with the capacity of physical activity at 95% confidence interval.

Sex differences in post‐inspiratory inspiratory activity and evolution of net respiratory muscle pressures during incremental exercise

The respiratory muscle pressure (Pmus) waveform allows observation of net inspiratory andexpiratory muscle recruitment under a wide variety of conditions, including mechanical ventilation, spontaneous breathing, and during exercise. Observation of the Pmus waveform during incremental and constant work rate cycling reveals that inspiratory and expiratory muscle recruitment systematically increase with rising minute ventilations. Additionally, measuring Pmus allows one to assess the post-inspiratory inspiratory muscle activity (PIIA), whereby the inspiratory muscles “brake” some or all of expiration to allow for a smoother transition in muscle recruitment. In recent years, it has become increasingly evident that the work of breathing is systematically higher for women compared with men at a given minute ventilation during exercise. It is possible that a greater evolution of net respiratory pressures, as well as longer PIIA duration, may be a contributing factor to the greater work of breathing observed in women during exercise. However, to date, no study has examined the potential sex differences in Pmus, nor PIIA, during exercise. Thus, a comprehensive assessment of the Pmus and PIIA during exercise between sexes is warranted. PURPOSE To compare PIIA and inspiratory and expiratory Pmus between men and women during incremental cycling. METHODS Fifteen women (21 ± 2 yrs; 167 ± 7 cm; 62 ± 7 kg) and 19 men (24 ± 4 yrs; 182 ± 5 cm; 81 ± 10 kg) visited the laboratory on two separate occasions. The first occasion was used to obtain informed consent and to screen participants for normal pulmonary function (>85% age-predicted). On the second visit, participants were instrumented with an esophageal balloon catheter to estimate variations in pleural pressure (Ppl). Quasi-static relaxation curves were obtained to measure chest wall recoil pressure (Pcw). Participants then completed an incremental cycling protocol until volitional exhaustion. Pmus was calculated at given minute ventilations during the exercise protocol as follows: Pmus = Pcw – Ppl. RESULTS Total Pmus (sum of average inspiratory and expiratory Pmus) was greater in women than men (P < 0.05). Peak inspiratory Pmus was similar between sexes, but peak expiratory Pmus was greater in women. The average rates of change (slope) in Pmus during inspiration and expiration were significantly faster in women than men at a given minute ventilation (P < 0.05). Finally, the duration of PIIA (expressed as a fraction of expiratory time) gradually decreased with increasing minute ventilation during exercise in both sexes (P < 0.05), but the decrease was comparable between sexes (P > 0.05). CONCLUSION The primary finding of this study was that the pattern of respiratory muscle recruitment was different between sexes during incremental cycling, given that women displayed systematically faster rates, and greater magnitude, of net inspiratory and expiratory pressure-development compared with men at matched ventilations. Additionally, the duration of PIIA was similar in both women and men, which implies no difference in the pattern of transition from inspiration to expiration between sexes.

Dynamic exercise changes in venous pressure and liver stiffness in Fontan patients: effects of Treprostinil.

Systemic venous hypertension and low cardiac output are believed to be important mediators of liver injury after the Fontan procedure. Pulmonary vasodilators have the potential to improve such haemodynamics. The aim of this study was to assess the acute effects of exercise on liver stiffness and venous pressures and to assess the impact of inhaled Treprostinil on this response. In this prospective, double-blind, placebo-controlled, crossover trial, 14 patients with a Fontan circulation were randomised to inhalation of placebo and Treprostinil. Incremental and constant work rate exercise tests were performed to assess the effect of Treprostinil on exercise tolerance. Venous pressures were measured throughout and liver stiffness at rest and immediately after peak exercise. Mean age was 27.8 ± 7.9 years and 66% were females. Exercise acutely increased liver stiffness by 30% (mean shear wave speed: 2.38 ± 0.71 versus 2.89 ± 0.51 ms, p = 0.02). Peripheral venous pressures increased acutely during both incremental (12.1 ± 2.4 versus 22.6 ± 8.0 mmHg, p < 0.001) and constant work rate exercise (12.5 ± 2.5 versus 23.4 ± 5.2 mmHg, p < 0.001). Overall, Treprostinil failed to attenuate exercise-induced increases in liver stiffness. Compared with placebo, Treprostinil did not significantly impact venous pressure responses, VO2peak, nor exercise endurance times. Peripheral venous pressure increased acutely during exercise by an average of 88% above baseline and was not altered by administration of inhaled Treprostinil. Liver stiffness measured immediately post-exercise increased acutely by an average of 30%, with no attenuation following Treprostinil inhalation.

Sex differences in the evolution of net respiratory muscle pressures during incremental exercise

The respiratory muscle pressure (Pmus) waveform lends insight into the patterns of net inspiratory v expiratory muscle recruitment under a wide variety of conditions, including mechanical ventilation, spontaneous breathing, and during exercise. On this last point, inspection of the Pmus waveform during incremental and constant work rate cycling reveals that inspiratory and expiratory muscle recruitment systematically increase with rising minute ventilations, and that the duration of post‐inspiratory inspiratory activity (PIIA) gradually disappears from low to high levels of respiratory motor output. In recent years, it has become increasingly evident that the work of breathing is systematically higher for women compared with men at a given minute ventilation during exercise. Yet, no study has examined the potential sex differences in the evolution of Pmus (and its components; e.g., PIIA) during exercise. Thus, a comprehensive assessment of the Pmus waveform during exercise between sexes is warranted.PurposeTo compare the evolution of inspiratory and expiratory Pmus between men and women during incremental cycling.MethodsThirteen men (21 ± yrs; 181 ± 5 cm; 82 ± 11 kg) and 10 women (21 ± 1 yrs; 165 ± 6 cm; 62 ± 6 kg) visited the laboratory on two separate occasions. The first occasion was used to obtain informed consent and to screen participants for normal pulmonary function (&gt;85% age‐predicted). On the second visit, participants were instrumented with an esophageal balloon catheter to estimate variations in pleural pressure (Ppl). Quasi‐static relaxation curves were obtained to measure chest wall recoil pressure (Pcw). Participants then completed an incremental cycling protocol until volitional exhaustion. Pmus was calculated at given minute ventilations during the exercise protocol as follows: Pmus = Pcw – Ppl.ResultsThe peak inspiratory Pmus were significantly greater in females compared with men at a given minute ventilation during incremental cycling (P &lt; 0.05), yet peak expiratory Pmus was similar between sexes. The average rates of change (slope) in Pmus during inspiration &amp; expiration were significantly faster in females than males at a given minute ventilation (P &lt; 0.05). Finally, the duration of PIIA (expressed as a fraction of expiratory time) gradually decreased with increasing minute ventilation during exercise (P &lt; 0.05). This reduction in PIIA was however similar between men and women.ConclusionThe primary finding of this study was that the pattern of respiratory muscle recruitment was different between sexes during incremental cycling, insofar as women displayed systematically larger inspiratory Pmus, and faster rates of net inspiratory &amp; expiratory pressure‐development compared with men at matched ventilations. However, no differences in PIIA between sexes were observed.Support or Funding InformationThis research was funded by preliminary data funds provided by Northern Arizona University (JWD). TJC was supported by the Irene Diamond Fund/American Federation for Aging Research Postdoctoral Transition Award during the time of this study.

Translating Ramp V˙O2 into Constant Power Output: A Novel Strategy that Minds the Gap.

This study aimed to model the dissociation in the V˙O2/power output (PO) relationship between ramp incremental (RI) and constant work rate (CWR) exercise and to develop a novel strategy that resolves this gap and enables an accurate translation of the RI V˙O2 response into a constant PO. Nine young men completed two RI tests (30 and 15 W·min) and CWR tests at seven intensities across exercise intensity domains. The V˙O2/PO relationship for RI and CWR exercise was modeled, and the dissociation was compared in terms of PO. The accuracy of three translation strategies was tested in the moderate-intensity (i.e., zone 1) and heavy-intensity (i.e., zone 2) domain. Strategy 1 comprised a simple mean response time correction, whereas strategies 2 and 3 accounted for the loss of mechanical efficiency in zone 2 by applying an extra correction that was based on, respectively, the difference between s2 - CWR and s2 - ramp and the ratio s2/s1. For all intensities, differences in PO were found between CWR and RI exercise (P < 0.001). Overall, these differences were smaller for the 15-W·min compared with the 30-W·min protocol (P = 0.012). Strategy 1 was accurate for PO selection in zone 1 (bias = 0.4 ± 7.3 W), but not in zone 2 (bias = 17.1 ± 15.9 W). Only strategy 2 was found to be accurate for both intensity zones (bias = 2.2 ± 14.2 W) (P = 0.107). This study confirmed that a simple mean response time correction works for PO selection in the moderate-intensity but not in the heavy-intensity domain. A novel strategy was tested and validated to accurately prescribe a constant PO based on the RI V˙O2 response in a population of young healthy men.

ERS statement on standardisation of cardiopulmonary exercise testing in chronic lung diseases.

The objective of this document was to standardise published cardiopulmonary exercise testing (CPET) protocols for improved interpretation in clinical settings and multicentre research projects. This document: 1) summarises the protocols and procedures used in published studies focusing on incremental CPET in chronic lung conditions; 2) presents standard incremental protocols for CPET on a stationary cycle ergometer and a treadmill; and 3) provides patients' perspectives on CPET obtained through an online survey supported by the European Lung Foundation. We systematically reviewed published studies obtained from EMBASE, Medline, Scopus, Web of Science and the Cochrane Library from inception to January 2017. Of 7914 identified studies, 595 studies with 26 523 subjects were included. The literature supports a test protocol with a resting phase lasting at least 3 min, a 3-min unloaded phase, and an 8- to 12-min incremental phase with work rate increased linearly at least every minute, followed by a recovery phase of at least 2-3 min. Patients responding to the survey (n=295) perceived CPET as highly beneficial for their diagnostic assessment and informed the Task Force consensus. Future research should focus on the individualised estimation of optimal work rate increments across different lung diseases, and the collection of robust normative data.

Validation Of Gas Analysis Over Incremental Work Intensities - A Comparison Of Two Metabolic Measurement Systems

Indirect calorimetry is a practical and accurate method of measuring metabolic gas exchange rate, specifically volume of oxygen and carbon dioxide (V̇O2 and V̇CO2). Commercial stationary and mobile systems typically include automated metabolic gas analyses. Metabolic cart systems are considered the standard; however, they pose limitations due to cost and portability. PURPOSE: To compare the accuracy of a commercially available mobile system (CareFusion Oxycon Mobile®, OXYCON) to a criterion stationary cart system (ParvoMedics TrueOne 2400®, PARVO). METHODS: Fifteen volunteers (13 Male, 2 Female; 24 ± 6 y (mean ± SD), 77 ± 13 kg BW, VO2peak 3.9 ± 0.7 L∙min-1) completed four trials over two non-consecutive study days. Trials consisted of a rest period, followed by three incremental treadmill work rates: walk (23-36% VO2peak), jog (49-67% VO2peak), and run (60-76% VO2peak) in controlled laboratory conditions (20 ± 0.5 °C; 45 ± 22 % RH). Metabolic system order was randomized and data collected was averaged over 3-4 minute steady-state periods from each work intensity. Correlation coefficients and systematic bias were used to evaluate the agreement between the systems. RESULTS: Measurements of V̇O2 from the OXYCON and PARVO were highly correlated (R2= 0.99). The OXYCON showed some positive bias (0.18 ± 0.16 L∙min-1) that increased with work intensity: rest (V̇O2 0.05 ± 0.06 L∙min-1), walk (V̇O2 0.15 ± 0.09 L∙min-1), jog (V̇O2 0.26 ± 0.16 L∙min-1), and run (V̇O2 0.31 ± 0.16 L∙min-1). CONCLUSION: The mobile OXYCON is an acceptable alternative to stationary metabolic cart systems for measuring metabolic gas exchange rate during rest and low intensity exercise. Clinicians may consider alternative devices for assessments at higher work intensities.

The prediction of endurance performance from work rates at fixed blood lactate concentrations is a mathematical not a physiological phenomenon - a novel hypothesis

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Work Performed Above The Respiratory Compensation Point Is Not Equivalent To W′

The hyperbolic power-time relationship for severe-intensity cycling exercise is defined by two physiological parameters: (i) the asymptote, critical power (CP); and (ii) the curvature constant, W′. Recently, we reported that the respiratory compensation point (RCP) displays poor measurement agreement with the CP. However, it is unknown whether the amount of supra-RCP mechanical work (RCP′) performed during ramp-incremental cycling is similar to that performed above the CP (i.e., W′). PURPOSE: We sought to determine the measurement agreement between W′ and RCP′ obtained during incremental cycling of varying ramp slopes. METHODS: Twelve male cyclists completed three separate ramp-incremental cycling protocols, where the work rate increment was slow (SR, 15 W[BULLET OPERATOR]min-1), medium (MR, 30 W[BULLET OPERATOR]min-1), or fast (FR, 45 W[BULLET OPERATOR]min-1). Initially, the RCP (adjusted for mean response time) was obtained using the ventilatory equivalent for CO method. To assess RCP′, we calculated the power–time integral between the RCP and the instantaneous power output observed at exercise termination for each ramp-incremental test, separately. W′ was determined via Morton’s model for ramp-incremental exercise. The assumption that W′ and RCP′ occur at equivalent kilojoule (kJ) values was assessed by one-way repeated- measures ANOVA and by evaluating the concordance correlation coefficient (CCC) and typical error (root-mean-square error [RMSE]) for each ramp-incremental test, separately. RESULTS:RCP′ decreased with increases in the ramp-incremental slope (P < 0.05). RCP′ in SR (21.5 ± 6.5 kJ), MR (16.8 ± 5.6 kJ) and FR (13.3 ± 4.3 kJ) were not different from W′ (15.7 ± 6.9 kJ). The degree to which the relationship between W′ and RCP′ approximated the line of identity was poor for SR (CCC = -0.09 and RMSE = 11.3 kJ), MR (CCC = 0.23 and RMSE = 7.5 kJ) and FR (CCC = 0.37 and RMSE = 6.5 kJ). CONCLUSION: Our data demonstrate that RCP′ is lower when the ramp-incremental slope is increased. Furthermore, despite occurring at similar kJ values, we observed poor measurement agreement between W′ and RCP′, as evidenced by the low CCC and the large RMSE values, irrespective of the ramp-incremental protocol. Together, these findings indicate that RCP′ obtained during ramp-incremental cycling is not equivalent to W′.

The Respiratory Compensation Point is Not a Valid Surrogate for Critical Power.

It is unclear whether the respiratory compensation point (RCP) may be used as a valid surrogate for critical power (CP). Accordingly, we sought to determine the measurement agreement between the CP and the RCP obtained during incremental cycling of varying ramp slopes. Eleven recreationally active men completed three separate ramp-incremental cycling protocols, where the work rate increment was slow (SR, 15 W·min), medium (MR, 30 W·min), or fast (FR, 45 W·min). The RCP was obtained using the ventilatory equivalent for CO2 output method. The CP was determined via Morton's model for ramp-incremental exercise. The assumption that the RCP and the CP occur at equivalent external work rates was assessed by one-way repeated-measures ANOVA and by evaluating the concordance correlation coefficient (CCC) and typical error (root-mean-square error [RMSE]) for each ramp protocol, separately. The external work rate corresponding to the RCP increased with increases in the ramp-incremental slope (P < 0.05). The RCP values in MR (268 ± 37 W) and FR (292 ± 41 W), but not SR (243 ± 35 W), were different (P < 0.05) from CP (247 ± 43 W). The degree to which the relationship between the CP and the RCP approximated the line of identity was relatively poor for SR (CCC = 0.73 and RMSE = 28 W), MR (CCC = 0.63 and RMSE = 36 W), and FR (CCC = 0.42 and RMSE = 55 W). Our data confirm that the external work rate associated with the RCP is labile and that these power outputs display poor measurement agreement with the CP. Taken together, these findings indicate that the RCP does not provide an accurate estimation of CP.

The Respiratory Compensation Point Is Not A Valid Surrogate Of Critical Power

There is a growing opinion in the literature that Critical Power (CP) may be confidently estimated from the respiratory compensation point (RCP) obtained during incremental cycling. Opponents of this view argue that any reported correspondence between the RCP and CP is coincidental. It is known that the RCP is labile: i.e., its manifestation defers to higher work rates during fast compared with slow incremental protocols. PURPOSE: We sought to examine the agreement between CP and the work rates corresponding to the RCP obtained during incremental cycling protocols of varying ramp slopes. METHODS: 11 recreationally-active men (23 ± 1 yr; 75 ± 2 kg; 179 ± 2 cm; peak O2 uptake: 53 ± 2 ml·kg-1·min-1) completed 3 separate incremental protocols, where the work rate increment was slow (SR: 15 W·min-1), medium (MR: 30 W·min-1) and fast (FR: 45 W·min-1). Protocol order was randomised. The gas-exchange threshold (GET) and RCP were obtained via computerised analysis of the relationships between O2 uptake and CO2 output, and CO2 output and expired ventilation, respectively. CP was determined via the 3-min “all-out” cycling test. The assumption that the RCP and CP occur at equivalent work rates was assessed by evaluating the concordance correlation coefficient (CCC), and root-mean square error (RMSE), between RCP and CP for each protocol, separately. RESULTS: The GET was similar across ramp protocols (pooled average: 149 ± 8 W). RCP augmented (P < 0.05) with increasing ramp slope (SR = 237 ± 9 W; MR = 253 ± 10 W; FR: 271 ± 10 W). The RCP work rates determined during each ramp protocol were not different from the group-mean CP (249 ± 8 W). The degree to which the relationship between RCP and CP approximated the “line-of-identity” was relatively poor for SR (CCC = 0.589; RMSE = 31 W), MR (CCC = 0.587; RMSE = 32 W) and FR (CCC = 0.438; RMSE = 30 W). CONCLUSIONS: Our findings agree with those of previous studies in that the work rate at RCP augments with increasing ramp slope during incremental cycling. Moreover, despite occurring at similar mean work rates, the relatively poor CCC and large RMSE between CP and RCP for each ramp protocol suggests that the RCP should not be considered a valid surrogate of the CP.

Thresholds in ventilation, cerebral and muscle oxygenation, and muscle activity during incremental cycling exercise

Introduction: Cycle time-trial performance is a function of the highest sustainable power output. The first (VT-1) and second (VT-2) ventilatory thresholds are practical tools for coaches and athletes to set training zones and exercise intensity. Specifically, VT-2 is closely linked to critical power, a primary determinant of endurance performance. The cascade of physiological events in the organs responsible for power production accompanying these respiratory thresholds remains contentious and yet to be fully characterized. Electromyographic (EMG) thresholds have been identified in leg muscles during incremental exercise while near infrared spectroscopy (NIRS) has revealed thresholds in both muscle deoxygenation and cerebral oxygenation towards the end of an incremental exercise test. However, the relative timing of the different muscle and brain oxygenation and muscle electrical activity responses to each other is unclear. Purpose: The aim of the present study was to examine the thresholds of cerebral and muscle oxygenation, along with muscle electrical activity during a ramp exercise test in relation to VT-1 and VT-2. Methods: Twenty-five recreational cyclists (mean±SD: age 37±8yrs, body mass 78±13kg, height 178±8cm, VO 2 max 53±8mL/kg/min) completed a ramp exercise test to exhaustion on an electromagnetically braked cycle-ergometer with a work rate increment of 25 W/min. Throughout the test, continuous measures of expired gas (breath-by-breath), prefrontal cortex and vastus lateralis (VL) oxygenation via NIRS, and EMG Root Mean Square activity for the VL, rectus femoris (RF), and biceps femoris (BF) muscles were recorded. Thresholds were defined by a double-linear model. Results: The results are summarized in Figure 1. VT-1 and VT-2 occurred at 57 ± 6% and 81 ± 6% of the exercise, respectively. There was a threshold in both cerebral deoxyhaemoglobin and oxyhaemoglobin (56±13% and 56±8% of exercise, respectively) which were not significantly different from VT-1 ( P >0.86, cohens d 0.8). Only one threshold could be identified for muscle parameters with a threshold in muscle oxyhaemoglobin (78±9% of exercise), attenuation in muscle deoxyhaemoglobin (80±8% of exercise), and increase in EMG activity of VL, RF and BF (89±5%, 82±14% and 85±9% of exercise, respectively). The thresholds in BF and VL EMG activity occurred after VT-2 ( P 0.6). Conclusion: The threshold in cerebral oxygenation parameters occurred at both VT-1 and VT-2. Conversely, the present investigation failed to support a role for VL muscle oxygenation and electrical activity at VT-1, but did display a threshold at or after VT-2. The changes in cerebral oxygenation and in BF and VL electrical activity occurred after VT-2, suggesting that the metabolic and ventilatory events characterizing this latter cardiorespiratory threshold may affect both cerebral and muscle oxygenation levels and subsequent muscle recruitment responses. These physiological mechanisms are important factors in describing key training concepts and performance capability; for instance critical power. Any marked rise in muscle recruitment above VT-2 or critical power will result in early onset of fatigue and limit exercise performance.

Acceptance and commitment therapy improves exercise tolerance in sedentary women.

To test the efficacy of an acute intervention derived from acceptance and commitment therapy (ACT) for increasing high-intensity constant work rate (CWR) cycle exercise tolerance in a group of low-active women age 18-45 yr. The secondary goals were to examine whether ACT would reduce perceived effort and improve in-task affect during exercise and increase postexercise enjoyment. In a randomized controlled trial, 39 women were randomized to either the experimental (using ACT-based cognitive techniques and listening to music during the CWR exercise tests) or a control group (listening to music during the CWR exercise tests). Before (CWR-1) and after the intervention (CWR-2), participants completed a CWR cycle exercise test at 80% of maximal incremental work rate (Wmax) until volitional exhaustion. On average, ACT (n = 18) and control (n = 21) groups were matched for age, body mass index, weekly leisure activity scores, and Wmax (all P > 0.05). Exercise tolerance time (ETT) increased by 15% from CWR-1 to CWR-2 for the ACT group (392.05 ± 146.4 vs 459.39 ± 209.3 s; mean ± SD) and decreased by 8% (384.71 ± 120.1 vs 353.86 ± 127.9 s) for the control group (P = 0.008). RPE were lower (e.g., by 1.5 Borg 6-20 scale units at 55% of ETT, P ≤ 0.01) during CWR-2 in the ACT versus that in the control group. By contrast, ACT had no effect on in-task affect. Exercise enjoyment was higher after CWR-2 in the ACT group versus that in the control group (P < 0.001). An acute ACT intervention increased high-intensity ETT and postexercise enjoyment and reduced perceived effort in low-active women. Further investigations of ACT as an effective intervention for enhancing the established health benefits of high-intensity exercise need to be provided.