Jonathan Wagner, Max Niemeyer, Denis InfangerID, Timo Hinrichs,Clement Guerra, Christopher Klenk,
Karsten Ko¨nigsteinID, Christian Cajochen, Arno Schmidt-Trucksa, Raphael KnaierID

https://doi.org/10.1371/journal.pone.0245306

Objective
This study compared the robustness of a V_ O2-plateau definition and a verification-phase
protocol to day-to-day and diurnal variations in determining the true V_ O2max. Further, the
additional value of a verification-phase was investigated.
Methods
Eighteen adults performed six cardiorespiratory fitness tests at six different times of the day
(diurnal variation) as well as a seventh test at the same time the sixth test took place (dayto-
day variation). A verification-phase was performed immediately after each test, with a
stepwise increase in intensity to 50%, 70%, and 105% of the peak power output.
Results
Participants mean V_ O2peak was 56 ± 8 mL/kg/min. Gwet’s AC1 values (95% confidence
intervals) for the day-to-day and diurnal variations were 0.64 (0.22, 1.00) and 0.71 (0.42,
0.99) for V_ O2-plateau and for the verification-phase 0.69 (0.31, 1.00) and 0.07 (−0.38, 0.52),
respectively. In 66% of the tests, performing the verification-phase added no value, while, in
32% and 2%, it added uncertain value and certain value, respectively, in the determination
of V_ O2max.
Conclusion
Compared to V_ O2-plateau the verification-phase shows lower reliability, increases costs
and only adds certain value in 2% of cases.

JONATHAN WAGNER, RAPHAEL KNAIER, DENIS INFANGER, KARSTEN KÖNIGSTEIN,
CHRISTOPHER KLENK, JUSTIN CARRARD, HENNER HANSSEN, TIMO HINRICHS,
DOUGLAS SEALS, and ARNO SCHMIDT-TRUCKSÄSS

Med. Sci. Sports Exerc., Vol. 53, No. 1, pp. 26–37, 2021.

Purpose: Cardiopulmonary exercise testing (CPET) is an importantmeasurement in clinical practice,
and its primary outcome, maximal oxygen uptake (V˙O2peak), is inversely associated with morbidity and mortality. The purposes of this study are to provide CPET reference values for maximal and submaximal parameters across the adult age spectrum of a healthy European cohort, to compare V˙O2peak values with other reference data sets, and to analyze the associations between physical activity (PA) levels and CPET parameters.
Methods: In this cross-sectional study, we prospectively recruited 502 participants (47% female) from 20 to 90 yr old. The subjects a CPET on a cycle ergometer using a ramp protocol. PA was objectively and continuously measured over 14 d using a triaxial accelerometer. Quantile curves were calculated for CPET parameters. To investigate the associations between CPET parameters and PA levels, linear regression analysis was performed. Results: V˙O2peak values observed in the group of 20–29 yr were 46.6 ± 7.9 and  39.3 ± 6.5 mL·kg−1⋅min−1 for males and females, respectively. On average, each age category (10-yr increments) showed a 10% lower V˙O2peak relative to the next younger age category. V˙O2peak values of previous studies were on average 7.5 mL·kg−1⋅min−1 (20%) lower for males and 6.5 mL·kg−1⋅min−1 (21%) lower for females. There was strong evidence supporting a positive association between theV˙O2peak (mL·kg−1⋅min−1) and the level of habitual PA performed at vigorous PA (estimate, 0.26; P < 0.001].
Conclusion: Maximal and submaximal CPET reference values over a large age range are novel, and differences to other studies are clinically highly relevant. Objectively measured vigorous-intensity PA showed a strong positive association with higher V˙O2peak and other performance-related CPET parameters, supporting
the implementation of higher-intensity aerobic exercise in health promotion.

Franssen WMA; Keytsman C; Marinus N; Verboven K; Eijnde BO; van Ryckeghem L; Dendale P; Zeevaert R;
Hansen D;

Journal of sport and health science [J Sport Health Sci] 2021 Jan 30. Date of Electronic Publication: 2021 Jan 30.

Background: Adults with obesity may display disturbed cardiac chronotropic responses during cardiopulmonary exercise testing (CPET), which relates to poor cardiometabolic health and an increased risk for adverse cardiovascular events. It is unknown whether cardiac chronotropic incompetence (CI) during maximal exercise is already present in obese adolescents and, if so, how that relates to cardiometabolic health.
Methods: Sixty-nine obese adolescents (body mass index (BMI) standard diviation score (SDS) 2.23 ± 0.32, age: 14.1 ± 1.2 years) and 29 lean adolescents (BMI SDS: -0.16 ± 0.84, age: 14.0 ± 1.5 years) performed a maximal CPET from which indicators for peak performance were determined. The resting heart rate (HR) and peak HR were used to calculate the maximal chronotropic response index. Biochemistry (lipid profile, glycemic control, inflammation, and leptin) was studied in fasted blood samples and during an oral glucose tolerance test within obese adolescents. Regression analyses were applied to examine associations between the presence of CI and blood or exercise capacity parameters, respectively, within obese adolescents.
Results: CI was prevalent in 32 out of 69 obese adolescents (46%) and 3 out of 29 lean adolescents (10%). C-reactive protein was significantly higher in obese adolescents with CI compared to obese adolescents without CI (p = 0.012). Furthermore, peak oxygen uptake and peak cycling power output were significantly reduced (p < 0.05) in obese adolescents with CI vs. obese adolescents without CI. The chronotropic index was independently related to blood total cholesterol (standardized coefficient (SC) β =-0.332; p = 0.012) and C-reactive protein concentration (SC β =-0.269; p = 0.039).
Conclusion: CI is more common in the current cohort of obese adolescents, and is related to systemic inflammation and exercise intolerance.

Terol Espinosa de Los Monteros C; Van der Palen RLF; Hazekamp MG; Rammeloo L; Jongbloed MRM; Blom NA; Harkel ADJT;

Pediatric cardiology [Pediatr Cardiol] 2021 Feb 01. Date of Electronic Publication: 2021 Feb 01.

After the arterial switch operation (ASO) for transposition of the great arteries (TGA), many patients have an impaired exercise tolerance. Exercise tolerance is determined with cardiopulmonary exercise testing by peak oxygen uptake (VO_2peak ). Unlike VO_2peak , the oxygen uptake efficiency slope (OUES) does not require a maximal effort for interpretation. The value of OUES has not been assessed in a large group of patients after ASO. The purpose of this study was to determine OUES and VO_2peak , evaluate its interrelationship and assess whether exercise tolerance is related to ventricular function after ASO. A cardiopulmonary exercise testing, assessment of physical activity score and transthoracic echocardiography (fractional shortening and left/right ventricular global longitudinal peak strain) were performed to 48 patients after ASO. Median age at follow-up after ASO was 16.0 (IQR 13.0-18.0) years. Shortening fraction was normal (36 ± 6%). Left and right global longitudinal peak strain were reduced: 15.1 ± 2.4% and 19.5 ± 4.5%. This group of patients showed lower values for all cardiopulmonary exercise testing parameters compared to the reference values: mean VO _2peak % 75% (95% CI 72-77) and mean OUES% 82(95% CI 77-87); without significant differences between subtypes of TGA. A strong-to-excellent correlation between the VO_2peak and OUES was found (absolute values: R = 0.90, p < 0.001; normalized values: R = 0.79, p < 0.001). No correlation was found between cardiopulmonary exercise testing results and left ventricle function parameters. In conclusion, OUES and VO_2peak were lower in patients after ASO compared to reference values but are strongly correlated, making OUES a valuable tool to use in this patient group when maximal effort is not achievable.

van der Steeg GE; Takken T;

European journal of applied physiology [Eur J Appl Physiol] 2021 Feb 01. Date of Electronic Publication:
2021 Feb 01.

Background: The maximum oxygen uptake (V₂ max) during cardiopulmonary exercise testing (CPET) is considered the best measure of cardiorespiratory fitness.
Aim: To provide up-to-date reference values for the VO ₂ max per kilogram of body mass (VO₂ max/kg) obtained by CPET in the Netherlands and Flanders.
Methods: The Lowlands Fitness Registry contains data from health checks among different professions and was used for this study. Data from 4612 apparently healthy subjects, 3671 males and 941 females, who performed maximum effort during cycle ergometry were analysed. Reference values for the VO₂ max/kg and corresponding centile curves were created according to the LMS method.
Results: Age had a negative significant effect (p < .001) and males had higher values of VO₂ max/kg with an overall difference of 18.0% compared to females. Formulas for reference values were developed: Males: VO₂ max/kg = - 0.0049 × age ²  + 0.0884 × age + 48.263 (R ²  = 0.9859; SEE = 1.4364) Females: VO₂ max/kg = - 0.0021 × age ²  – 0.1407 × age + 43.066 (R ²  = 0.9989; SEE = 0.5775). Cross-validation showed no relevant statistical mean difference between measured and predicted values for males and a small but significant mean difference for females. We found remarkable higher VO₂ max/kg values compared to previously published studies.
Conclusions: This is the first study to provide reference values for the VO₂ max/kg based on a Dutch/Flemish cohort. Our reference values can be used for a more accurate interpretation of the VO₂ max in the West-European population.

Geertje E. van der Steeg · Tim Takken

European Journal of Applied Physiology https://doi.org/10.1007/s00421-021-04596-6

Background The maximum oxygen uptake (VO2max) during cardiopulmonary exercise testing (CPET) is considered the best measure of cardiorespiratory fitness. AimTo provide up-to-date reference values for the VO2max per kilogram of body mass (VO2max/kg) obtained by CPET in the Netherlands and Flanders.
Methods The Lowlands Fitness Registry contains data from health checks among different professions and was used for this study. Data from 4612 apparently healthy subjects, 3671 males and 941 females, who performed maximum effort during cycle ergometry were analysed. Reference values for the VO2max/kg and corresponding centile curves were created according to the LMS method.
Results Age had a negative significant effect (p < .001) and males had higher values of VO2max/kg with an overall difference of 18.0% compared to females. Formulas for reference values were developed:
• Males: VO2max/kg = − 0.0049 × age2 + 0.0884 × age + 48.263 (R2 = 0.9859; SEE = 1.4364)
• Females: VO2max/kg = − 0.0021 × age2 − 0.1407 × age+ 43.066 (R2 = 0.9989; SEE = 0.5775).
Cross-validation showed no relevant statistical mean difference between measured and predicted values for males and a small but significant mean difference for females. We found remarkable higher VO2max/kg values compared to previously published studies.
Conclusions This is the first study to provide reference values for the VO2max/kg based on a Dutch/Flemish cohort. Our reference values can be used for a more accurate interpretation of the VO2max in the West-European population.

Berton DC;  Gass R; Feldmann B; Plachi F; Hutten D; Mendes NBS; Schroeder E; Balzan FM; Peyré-Tartaruga LA; Gazzana MB;

The clinical respiratory journal [Clin Respir J] 2021 Jan; Vol. 15 (1), pp. 26-35. Date of Electronic Publication: 2020 Sep 15.

Introduction: Inspiratory muscle weakness (IMW) is a potential cause of exertional dyspnea frequently under-appreciated in clinical practice. Cardiopulmonary exercise testing (CPET) is usually requested as part of the work-up for unexplained breathlessness, but the specific pattern of exercise responses ascribed to IMW is insufficiently characterized.
Objectives: To identify the physiological and sensorial responses to progressive exercise in dyspneic patients with IMW without concomitant cardiorespiratory or neuromuscular diseases.
Methods: Twenty-three subjects (18 females, 55.2 ± 16.9 years) complaining of chronic daily life dyspnea (mMRC = 3 [2-3]) plus maximal inspiratory pressure < the lower limit of normal and 12 matched controls performed incremental cycling CPET. FEV ₁ /FVC<0.7, significant abnormalities in chest CT or echocardiography, and/or an established diagnosis of neuromuscular disease were among the exclusion criteria.
Results and Conclusion: Patients presented with reduced aerobic capacity (peak V̇O ₂ : 79 ± 26 vs 116 ± 21 %predicted), a tachypneic breathing pattern (peak breathing frequency/tidal volume = 38.4 ± 22.7 vs 21.7 ± 14.2 breaths/min/L) and exercise-induced inspiratory capacity reduction (-0.17 ± 0.33 vs 0.10 ± 0.30 L) (all P < .05) compared to controls. In addition, higher ventilatory response (ΔV̇ _E /ΔV̇CO ₂ = 34.1 ± 6.7 vs 27.0 ± 2.3 L/L) and symptomatic burden (dyspnea and leg discomfort) to the imposed workload were observed in patients. Of note, pulse oximetry was similar between groups. Reduced aerobic capacity in the context of a tachypneic breathing pattern, inspiratory capacity reduction and preserved oxygen exchange during progressive exercise should raise the suspicion of inspiratory muscle weakness in subjects with otherwise unexplained breathlessness.

Chambers DJ; Wisely NA;

BJA education [BJA Educ] 2019 May; Vol. 19 (5), pp. 158-164. Date of Electronic Publication: 2019 Mar 20.

NO ABSTRACT AVAILABLE

Arena R; Myers J; Harber M; Phillips SA; Severin R; Ozemek C; Peterman JE; Kaminsky LA

Journal of cardiopulmonary rehabilitation and prevention [J Cardiopulm Rehabil Prev] 2021 Jan 14. Date of Electronic Publication: 2021 Jan 14.

Purpose: Cardiopulmonary exercise testing (CPX) is the gold standard approach for the assessment of cardiorespiratory fitness (CRF). The primary aim of the current study was to determine reference standards for the minute ventilation/carbon dioxide production (V˙E/V˙CO2) slope in a cohort from the “Fitness Registry and the Importance of Exercise: A National Database” (FRIEND) Registry.
Methods: The current analysis included 2512 tests from 10 CPX laboratories in the United States. Inclusion criteria included CPX data on apparently healthy men and women: (1) age ≥20 yr; and (2) with a symptom-limited exercise test performed on a treadmill. Ventilation and V˙CO2 data, from the initiation of exercise to peak, were used to calculate the V˙E/V˙CO2 slope via least-squares linear regression. Reference values were determined for men and women by decade of life.
Results: On average, V˙E/V˙CO2 slope values were lower in men and increased with age independent of sex. Fiftieth percentile values increased from 27.1 in the second decade to 33.9 in the eighth decade in men and from 28.5 in the second decade to 33.7 in the eighth decade in women. In the overall group, correlations with baseline characteristics and the V˙E/V˙CO2 slope were statistically significant (P < .05) although generally weak, particularly for age and body mass index.
Conclusion: The results of the current study establish reference values for the V˙E/V˙CO2 slope when treadmill testing is performed, and all exercise data are used for the slope calculation. These results may prove useful in enhancing the interpretation of CPX results when assessing CRF.