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.

Zaqout M; Vandekerckhove K; De Wolf D; Panzer J; Bové T; François K; De Henauw S; Michels N;

Pediatric cardiology [Pediatr Cardiol] 2021 Jan 23. Date of Electronic Publication: 2021 Jan 23.

The aim of this study was to determine factors associated with physical fitness (PF) in children who underwent surgery for congenital heart disease (CHD). Sixty-six children (7-14 years) who underwent surgery for ventricular septal defect (n = 19), transposition of great arteries (n = 22), coarctation of aorta (n = 10), and tetralogy of Fallot (n = 15) were included. All children performed PF tests: cardiorespiratory fitness, upper- and lower-limb muscle strength, speed, balance, and flexibility. Cardiac evaluation was done via echocardiography and cardiopulmonary exercise test. Factors related to child’s characteristics, child’s lifestyle, physical activity motivators/barriers, and parental factors were assessed. Linear regression analyses were conducted. The results showed no significant differences in physical activity (PA) level by CHD type. Boys had better cardiorespiratory fitness (difference = 1.86 ml/kg/min [0.51;3.22]) and were more physically active (difference = 19.40 min/day [8.14;30.66]), while girls had better flexibility (difference = - 3.60 cm [- 7.07;- 0.14]). Physical activity motivators showed an association with four out of six PF components: cardiorespiratory fitness, coefficient = 0.063 [0.01;0.11]; upper-limb muscle strength, coefficient = 0.076 [0.01;0.14]; lower-limb muscle strength, coefficient = 0.598 [0.07;1.13]; and speed, coefficient = 0.03 [0.01;0.05]. Age, sex, and motivators together reached a maximum adjusted R ²  = 0.707 for upper-limb strength. Adding other possible determinants did not significantly increase the explained variance. Apart from age and sex as non-modifiable determinants, the main target which might improve fitness would be the introduction of an intervention which increases the motivation to be active.

Tagashira S; Kurose S; Kimura Y;

Heart and vessels [Heart Vessels] 2021 Jan 23. Date of Electronic Publication: 2021 Jan 23.

Anaerobic threshold (AT) from cardiopulmonary exercise tests (CPX) is the standard for measuring exercise intensity among patients with cardiovascular disease in Japan. However, it remains controversial whether AT represents the safety limit for exercise intensity in patients with cardiovascular disease. The purpose of this study was to investigate cardiac rehabilitation (CR) efficacy and safety with exercise intensities above the AT and at a traditional AT in a randomized trial. The participants included 57 patients who were admitted to the outpatient CR unit with a diagnosis of acute myocardial infarction. The participants were randomly divided as follows: 25 patients in the AT group, who performed aerobic exercises with an intensity at the AT; and 32 patients in the “Over AT” group, who performed exercises at an intensity higher than the AT. The following components were measured: maximum oxygen uptake (peak VO ₂ ), oxygen uptake at the AT (AT VO ₂ ), increase in oxygen uptake during exercise (ΔVO ₂ /ΔWR) during the CPX, vascular endothelial function test (%FMD: the percentage of flow-mediated dilation), and isometric knee extension strength. The measurements were obtained at the start of the exercise therapy and after 2, 3, and 4 months. They were compared within and between groups, and the correlation between the rates of improvement was investigated. Peak VO ₂ , AT VO ₂ , ΔVO ₂ /ΔWR, and %FMD had significantly improved after 3 months in both groups. The isometric knee extension strength had improved in the “Over AT” group after 2 months. Interactions were observed with peak VO ₂ , ΔVO ₂ /ΔWR, and isometric knee extension strength. However, %FMD was not significantly different between the groups. In the “Over AT” group, the rate of improvement in peak VO ₂ was positively correlated with the improvement in the isometric knee extension strength (r = 0.61, p < 0.001), but not with %FMD. These data suggest that exercise at an intensity above the AT improved exercise tolerance faster than that at the AT, and this improvement rate was associated with changes in isometric knee extension strength.

Herrod PJJ; Blackwell JEM; Boereboom CL; Atherton PJ; Williams JP; Lund JN; Phillips BE;

Aging medicine (Milton (N.S.W)) [Aging Med (Milton)] 2020 Sep 17; Vol. 3 (4), pp. 245-251. Date of Electronic Publication: 2020 Sep 17 (Print Publication: 2020).

Objective: High-intensity interval training (HIIT) has been shown to be more effective than moderate continuous aerobic exercise for improving cardiorespiratory fitness (CRF) in a limited time frame. However, the length of time required for HIIT to elicit clinically significant improvements in the CRF of older adults is currently unknown. The aim of this study was to compare changes in the CRF of older adults completing identical HIIT protocols of varying durations.
Methods: Forty healthy, community-dwelling older adults completed a cardiopulmonary exercise test (CPET) before and after 2, 4, or 6 weeks of fully supervised HIIT on a cycle ergometer, or a no-intervention control period.
Results: Anaerobic threshold (AT) was increased only after 4 (+1.9 [SD 1.1] mL/kg/min) and 6 weeks (+1.9 [SD 1.8] mL/kg/min) of HIIT (both P  < 0.001), with 6-week HIIT required to elicit improvements in VO ₂ peak (+3.0 [SD 6] mL/kg/min; P  = 0.04). Exercise tolerance increased after 2 (+15 [SD 15] W), 4 (+17 [SD 11] W), and 6 weeks (+16 [SD 11] W) of HIIT (all P  < 0.001), with no difference in increase between the groups. There were no changes in any parameter in the control group.
Conclusion: Improvements in exercise tolerance from HIIT precede changes in CRF. Just 4 weeks of a well-tolerated, reduced-exertion HIIT protocol are required to produce significant changes in AT, with a further 2 weeks of training also eliciting improvements in VO ₂ peak.

Baumbach P; Schmidt-Winter C; Hoefer J; Derlien S; Best N; Herbsleb M; Coldewey SM;

Frontiers in medicine [Front Med (Lausanne)] 2020 Dec 21; Vol. 7, pp. 585462. Date of Electronic Publication: 2020 Dec 21 (Print Publication: 2020).

Background: Mitochondria are the key players in aerobic energy generation via oxidative phosphorylation. Consequently, mitochondrial function has implications on physical performance in health and disease ranging from high performance sports to critical illness. The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) allows in vivo measurements of mitochondrial oxygen tension (mitoPO ₂ ). Hitherto, few data exist on the relation of mitochondrial oxygen metabolism and ergospirometry-derived variables during physical performance. This study investigates the association of mitochondrial oxygen metabolism with gas exchange and blood gas analysis variables assessed during cardiopulmonary exercise testing (CPET) in aerobic and anaerobic metabolic phases. Methods: Seventeen volunteers underwent an exhaustive CPET (graded multistage protocol, 50 W/5 min increase), of which 14 were included in the analysis. At baseline and for every load level PpIX-TSLT-derived mitoPO ₂ measurements were performed every 10 s with 1 intermediate dynamic measurement to obtain mitochondrial oxygen consumption and delivery (mito V . O ₂ , mito D . O ₂ ). In addition, variables of gas exchange and capillary blood gas analyses were obtained to determine ventilatory and lactate thresholds (VT, LT). Metabolic phases were defined in relation to VT1 and VT2 (aerobic: <VT1, aerobic-anaerobic transition: ≥VT1 and <VT2 and anaerobic: ≥VT2). We used linear mixed models to compare variables of PpIX-TSLT between metabolic phases and to analyze their associations with variables of gas exchange and capillary blood gas analyses.
Results: MitoPO ₂ increased from the aerobic to the aerobic-anaerobic phase followed by a subsequent decline. A mitoPO ₂ peak, termed mitochondrial threshold (MT), was observed in most subjects close to LT2. Mito D . O ₂ increased during CPET, while no changes in mito V . O ₂ were observed. MitoPO ₂ was negatively associated with partial pressure of end-tidal oxygen and capillary partial pressure of oxygen and positively associated with partial pressure of end-tidal carbon dioxide and capillary partial pressure of carbon dioxide. Mito D . O ₂ was associated with cardiovascular variables. We found no consistent association for mito V . O ₂ .
Conclusion: Our results indicate an association between pulmonary respiration and cutaneous mitoPO ₂ during physical exercise. The observed mitochondrial threshold, coinciding with the metabolic transition from an aerobic to an anaerobic state, might be of importance in critical care as well as in sports medicine.

Dayton JD; Ford K; Carroll SJ; Flynn PA; Kourtidou S; Holzer RJ;

Pediatric cardiology [Pediatr Cardiol] 2021 Jan 04. Date of Electronic Publication: 2021 Jan 04.

The COVID-19 pandemic has had devastating direct consequences on the health of affected patients. It has also had a significant impact on the ability of unaffected children to be physically active. We evaluated the effect of deconditioning from social distancing and school shutdowns implemented during the COVID-19 pandemic on the cardiovascular fitness of healthy unaffected children. This is a single-center, retrospective case-control study performed in an urban tertiary referral center. A cohort of 10 healthy children that underwent cardiopulmonary exercise testing after COVID-19 hospital restrictions were lifted was compared to a matched cohort before COVID-19-related shutdowns on school and after-school activities. Comparisons of oxygen uptake (VO ₂ ) max and VO ₂ at anaerobic threshold between the pre- and post-COVID-19 cohorts were done. The VO ₂ max in the post-COVID cohort was significantly lower than in the pre-COVID cohort (39.1 vs. 44.7, p = 0.031). Only one out of ten patients had a higher VO ₂ max when compared to their matched pre-COVID control and was also the only patient with a documented history of participation in varsity-type athletics. The percentile of predicted VO ₂ was significantly lower in the post-COVID cohort (95% vs. 105%, p = 0.042). This study for the first time documented a significant measurable decline in physical fitness of healthy children as a result of the COVID-19 pandemic and its associated restrictions. Measures need to be identified that encourage and facilitate regular exercise in children in a way that are not solely dependent on school and organized after-school activities.