EURO PEAN SO CIETY O F CARDIOLOGY ®
Original scientific paper
Validation of a brief step-test protocol for estimation of peak oxygen uptake Frank Beutner1,2,*, Romy Ubrich1,*, Silke Zachariae1,3, Christoph Engel1,3, Marcus Sandri2, Andrej Teren1,2 and Stephan Gielen1,4
European Journal of Preventive Cardiology 2015, Vol. 22(4) 503–512 ! The European Society of Cardiology 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/2047487314533216 ejpc.sagepub.com
Abstract Background: Physical exercise capacity has been shown to predict cardiovascular disease incidence and is increasingly measured in epidemiological studies. However, direct measurement of peak oxygen uptake is too time consuming in large-scale studies. We therefore investigated whether a brief 3-minute step-test protocol can be used to estimate peak oxygen uptake in these settings. Design and methods: A group of 97 subjects performed the YMCA step test and a maximal treadmill test with continuous measurement of oxygen uptake. Correlation and linear regression analyses were used to identify VO2peak predictors obtained from the step test and to develop models for VO2peak estimation. Results: The YMCA model, including the 1-minute heart beat count, predicted VO2peak with R ¼ 0.83. A novel simplified model based on the heart rate at 45 s of recovery performed comparable (R ¼ 0.83). However, models based on heart rate measures were only valid in subjects who completed the test according to protocol, but not in subjects who terminated prematurely. For the applicability in subjects with low exercise capacity, a new model including gas exchange analysis enabled prediction of VO2peak (R ¼ 0.89). All models were validated in an independent sample (r ¼ 0.86–0.91). Exercise time of the step test was less than one-hird of standard ergospirometry (treadmill test: 654 151 s, step test: 180 s, p < 0.001). Conclusion: In large-scale epidemiological studies with limited time slots for exercise testing and significant proportions of subjects with low exercise capacity a modified version of the YMCA step test may be used to predict VO2peak.
Keywords step test, maximum oxygen uptake, VO2max, VO2peak, exercise testing Received 7 November 2013; accepted 7 April 2014
Introduction Physical fitness has been identified as a predictor of mortality and cardiovascular events in long-term follow-up studies both among cardiovascular patients and healthy subjects.1–7 However, standard maximal exercise testing using direct measurement of peak oxygen uptake (VO2peak) is time consuming and may therefore not be feasible in certain settings (e.g. largescale epidemiological studies, primary health care, etc.).8 In consequence, there is a clear need for a brief cardiovascular fitness test, which can be performed as part of a multifaceted health assessment battery. Single-stage, fixed-time step tests, such as the commonly used Young Men’s Christian Association (YMCA) step test, could be used to predict VO2peak.9 The step test was originally developed by Kasch in 1961,
using the heart beat count (HBC) after the first minute of recovery to predict maximum oxygen uptake.10,11 1 LIFE – Leipzig Research Center for Civilization Diseases, Medical Faculty, University Leipzig, Leipzig, Germany 2 Heart Center University Leipzig, Department of Internal Medicine/ Cardiology, Leipzig, Germany 3 Institute for Medical Informatics, Statistics and Epidemiology, University Leipzig, Leipzig, Germany 4 Department of Medicine III, Martin Luther University Halle-Wittenberg, University Hospital Halle, Halle/Saale, Germany
*Frank Beutner and Romy Ubrich contributed equally to this paper. Corresponding author: Stephan Gielen, Department of Internal Medicine III, University Hospital, Martin Luther University of Halle/Wittenberg, Ernst-Grube-Strasse 40, 06120 Halle, Germany. Email: [email protected]
504 The National YMCA recognized the test as a simple and time-effective method for categorization of individual fitness levels in the target population of young healthy men and adopted Kasch’s step test as part of the National YMCA Physical Fitness Test Battery. Robust correlations have been repeatedly observed between VO2peak and HBCs obtained from modified step test protocols.12–17 However, alternative cardiorespiratory measures during a step test have never been studied for estimation of individual VO2peak. Thus, the aim of the present study was: 1. to analyse the individual physiological response during the YMCA step test using continuous heart rate monitoring and gas exchange measurement; 2. to compare VO2peak prediction by a model using the standard 1-minute post-exercise HBC with new models using multivariate regression based on additional cardiorespiratory measurements during the step test; and 3. to reflect whether the YMCA step test is suited for VO2peak prediction in population-based studies.
Methods Study sample Subjects were recruited as participants of the LIFE Project (Leipzig Research Center for Civilization Diseases), a combined large-scale population- and disease-based epidemiological cohort study conducted in the city of Leipzig, Germany. LIFE aims to study the interaction between genetic, environmental and individual lifestyle factors on the risk of various civilization diseases. In this feasibility study a total of 111 subjects (55 men, 56 women aged 22–79 years) completed a maximum treadmill test in addition to the selected exercise test battery including step test, hand grip test and physical activity questionnaires. Subjects with ECG abnormalities, severe pulmonary or cardiovascular diseases, orthopaedic disabilities or taking beta blocker medication were excluded from the active exercise studies. The Ethics Committee at the University of Leipzig approved the study protocol. All participants gave their written informed consent prior to study inclusion.
European Journal of Preventive Cardiology 22(4) cardiopulmonary treadmill exercise test with determination of VO2peak (at respiratory exchange rates > 1.1). A minimum period of 2 hours of rest was given between the two exercise tests. Participants were introduced to the programme and familiarized with the test protocols before starting the test battery.
Step test We adopted basic characteristics of the YMCA step test including a 12-inch bench height, a duration of 3 minutes and the metronome-based step frequency (96 beats per minute) of 24 step cycles per minute.9 Instead of counting post-exercise 1-minute HBC manually, we continuously recorded the heart rate using a POLAR single channel ECG chest belt device (RS800CX, POLAR Electro, Germany) starting at 2 minutes prior to stepping and finishing 5 minutes after workload termination. The POLAR system together with a wireless electrode chest belt allows detection of R-R intervals with a resolution of 1 ms.18 POLAR was set to store heart rate in 5 s intervals continuously during all test phases. The test started with a 2-minute resting phase while subjects were seated on a chair in a temperature- and humidity-controlled quiet room. Subjects had to step 72 times in 3 minutes on the prepared box (step upup-down-down). Stepping frequency was indicated by a metronome. Finally, subjects were seated again during a 5-minute recovery phase. Participants were categorized in sets of subjects who finished the step test conforming to protocol, i.e. kept up stepping for 3 minutes and managed to do at least 70 steps (completers) and subjects who terminated the test prematurely or did not achieve 70 steps (noncompleters). The 1-minute heart beat count (1 min-HBC) as defined by the original YMCA step test was approximated calculating the mean of twelve consecutive POLAR heart rate records in 5 s-intervals, starting 5 s after workload termination. Similarly, we calculated continuous HBCs in 5 s intervals from 15 s to 2 minutes of the post-exercise. In order to evaluate the exercise intensity of the YMCA step-test protocol, the oxygen uptake was measured using a breath-by-breath gas exchange analysis system (MasterScreen CPX, CareFusion, Hoechberg, Germany) during the step test.
Study protocol Testing was performed between 7.30 a.m. and 3.30 p.m. Exercise capacity was assessed by (1) the standardized YMCA step test with continuous heart rate monitoring by a single channel ECG and a breath-by-breath analysis of oxygen uptake and (2) a maximal
Standard treadmill cardiopulmonary exercise testing The peak oxygen uptake (VO2peak) was measured using the same breath-by-breath analysis system during an exhaustion-limited treadmill exercise test (MasterScreen CPX, CareFusion, Hoechberg,
Beutner et al. Germany). According to the ACC/AHA guidelines for exercise testing, the treadmill protocol was customized individually to achieve maximal capacity within 6– 12 minutes.19 Self-reported exercise capacity by the Veterans Physical Activity Questionnaire (VSAQ) was used for protocol alignment.20 The Bruce protocol was used for individuals having VSAQ metabolic equivalent (MET) 9 and the modified Bruce protocol was used for individuals having VSAQ MET 6. Individuals having intermediate VSAQ MET 7/8 were assigned to Bruce protocol when step-test criteria were fulfilled; otherwise they were assigned to the modified protocol. The protocol began with a 1-minute warm-up, during which participants walked comfortably at selfpaced speed and at 0% grade. The workload was then increased according to the Bruce or modified Bruce protocol, respectively.21 Oxygen uptake was considered maximal if any two of the following criteria were met: (a) respiratory exchange ratio 1.1; (b) a heart rate at or near agepredicted peak (220-age 10 beats/min); and (c) when further increase in workload did not result in a significant rise in oxygen uptake (60 years, female gender, BMI >29 kgm2, VSAQ score
Original scientific paper
Validation of a brief step-test protocol for estimation of peak oxygen uptake Frank Beutner1,2,*, Romy Ubrich1,*, Silke Zachariae1,3, Christoph Engel1,3, Marcus Sandri2, Andrej Teren1,2 and Stephan Gielen1,4
European Journal of Preventive Cardiology 2015, Vol. 22(4) 503–512 ! The European Society of Cardiology 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/2047487314533216 ejpc.sagepub.com
Abstract Background: Physical exercise capacity has been shown to predict cardiovascular disease incidence and is increasingly measured in epidemiological studies. However, direct measurement of peak oxygen uptake is too time consuming in large-scale studies. We therefore investigated whether a brief 3-minute step-test protocol can be used to estimate peak oxygen uptake in these settings. Design and methods: A group of 97 subjects performed the YMCA step test and a maximal treadmill test with continuous measurement of oxygen uptake. Correlation and linear regression analyses were used to identify VO2peak predictors obtained from the step test and to develop models for VO2peak estimation. Results: The YMCA model, including the 1-minute heart beat count, predicted VO2peak with R ¼ 0.83. A novel simplified model based on the heart rate at 45 s of recovery performed comparable (R ¼ 0.83). However, models based on heart rate measures were only valid in subjects who completed the test according to protocol, but not in subjects who terminated prematurely. For the applicability in subjects with low exercise capacity, a new model including gas exchange analysis enabled prediction of VO2peak (R ¼ 0.89). All models were validated in an independent sample (r ¼ 0.86–0.91). Exercise time of the step test was less than one-hird of standard ergospirometry (treadmill test: 654 151 s, step test: 180 s, p < 0.001). Conclusion: In large-scale epidemiological studies with limited time slots for exercise testing and significant proportions of subjects with low exercise capacity a modified version of the YMCA step test may be used to predict VO2peak.
Keywords step test, maximum oxygen uptake, VO2max, VO2peak, exercise testing Received 7 November 2013; accepted 7 April 2014
Introduction Physical fitness has been identified as a predictor of mortality and cardiovascular events in long-term follow-up studies both among cardiovascular patients and healthy subjects.1–7 However, standard maximal exercise testing using direct measurement of peak oxygen uptake (VO2peak) is time consuming and may therefore not be feasible in certain settings (e.g. largescale epidemiological studies, primary health care, etc.).8 In consequence, there is a clear need for a brief cardiovascular fitness test, which can be performed as part of a multifaceted health assessment battery. Single-stage, fixed-time step tests, such as the commonly used Young Men’s Christian Association (YMCA) step test, could be used to predict VO2peak.9 The step test was originally developed by Kasch in 1961,
using the heart beat count (HBC) after the first minute of recovery to predict maximum oxygen uptake.10,11 1 LIFE – Leipzig Research Center for Civilization Diseases, Medical Faculty, University Leipzig, Leipzig, Germany 2 Heart Center University Leipzig, Department of Internal Medicine/ Cardiology, Leipzig, Germany 3 Institute for Medical Informatics, Statistics and Epidemiology, University Leipzig, Leipzig, Germany 4 Department of Medicine III, Martin Luther University Halle-Wittenberg, University Hospital Halle, Halle/Saale, Germany
*Frank Beutner and Romy Ubrich contributed equally to this paper. Corresponding author: Stephan Gielen, Department of Internal Medicine III, University Hospital, Martin Luther University of Halle/Wittenberg, Ernst-Grube-Strasse 40, 06120 Halle, Germany. Email: [email protected]
504 The National YMCA recognized the test as a simple and time-effective method for categorization of individual fitness levels in the target population of young healthy men and adopted Kasch’s step test as part of the National YMCA Physical Fitness Test Battery. Robust correlations have been repeatedly observed between VO2peak and HBCs obtained from modified step test protocols.12–17 However, alternative cardiorespiratory measures during a step test have never been studied for estimation of individual VO2peak. Thus, the aim of the present study was: 1. to analyse the individual physiological response during the YMCA step test using continuous heart rate monitoring and gas exchange measurement; 2. to compare VO2peak prediction by a model using the standard 1-minute post-exercise HBC with new models using multivariate regression based on additional cardiorespiratory measurements during the step test; and 3. to reflect whether the YMCA step test is suited for VO2peak prediction in population-based studies.
Methods Study sample Subjects were recruited as participants of the LIFE Project (Leipzig Research Center for Civilization Diseases), a combined large-scale population- and disease-based epidemiological cohort study conducted in the city of Leipzig, Germany. LIFE aims to study the interaction between genetic, environmental and individual lifestyle factors on the risk of various civilization diseases. In this feasibility study a total of 111 subjects (55 men, 56 women aged 22–79 years) completed a maximum treadmill test in addition to the selected exercise test battery including step test, hand grip test and physical activity questionnaires. Subjects with ECG abnormalities, severe pulmonary or cardiovascular diseases, orthopaedic disabilities or taking beta blocker medication were excluded from the active exercise studies. The Ethics Committee at the University of Leipzig approved the study protocol. All participants gave their written informed consent prior to study inclusion.
European Journal of Preventive Cardiology 22(4) cardiopulmonary treadmill exercise test with determination of VO2peak (at respiratory exchange rates > 1.1). A minimum period of 2 hours of rest was given between the two exercise tests. Participants were introduced to the programme and familiarized with the test protocols before starting the test battery.
Step test We adopted basic characteristics of the YMCA step test including a 12-inch bench height, a duration of 3 minutes and the metronome-based step frequency (96 beats per minute) of 24 step cycles per minute.9 Instead of counting post-exercise 1-minute HBC manually, we continuously recorded the heart rate using a POLAR single channel ECG chest belt device (RS800CX, POLAR Electro, Germany) starting at 2 minutes prior to stepping and finishing 5 minutes after workload termination. The POLAR system together with a wireless electrode chest belt allows detection of R-R intervals with a resolution of 1 ms.18 POLAR was set to store heart rate in 5 s intervals continuously during all test phases. The test started with a 2-minute resting phase while subjects were seated on a chair in a temperature- and humidity-controlled quiet room. Subjects had to step 72 times in 3 minutes on the prepared box (step upup-down-down). Stepping frequency was indicated by a metronome. Finally, subjects were seated again during a 5-minute recovery phase. Participants were categorized in sets of subjects who finished the step test conforming to protocol, i.e. kept up stepping for 3 minutes and managed to do at least 70 steps (completers) and subjects who terminated the test prematurely or did not achieve 70 steps (noncompleters). The 1-minute heart beat count (1 min-HBC) as defined by the original YMCA step test was approximated calculating the mean of twelve consecutive POLAR heart rate records in 5 s-intervals, starting 5 s after workload termination. Similarly, we calculated continuous HBCs in 5 s intervals from 15 s to 2 minutes of the post-exercise. In order to evaluate the exercise intensity of the YMCA step-test protocol, the oxygen uptake was measured using a breath-by-breath gas exchange analysis system (MasterScreen CPX, CareFusion, Hoechberg, Germany) during the step test.
Study protocol Testing was performed between 7.30 a.m. and 3.30 p.m. Exercise capacity was assessed by (1) the standardized YMCA step test with continuous heart rate monitoring by a single channel ECG and a breath-by-breath analysis of oxygen uptake and (2) a maximal
Standard treadmill cardiopulmonary exercise testing The peak oxygen uptake (VO2peak) was measured using the same breath-by-breath analysis system during an exhaustion-limited treadmill exercise test (MasterScreen CPX, CareFusion, Hoechberg,
Beutner et al. Germany). According to the ACC/AHA guidelines for exercise testing, the treadmill protocol was customized individually to achieve maximal capacity within 6– 12 minutes.19 Self-reported exercise capacity by the Veterans Physical Activity Questionnaire (VSAQ) was used for protocol alignment.20 The Bruce protocol was used for individuals having VSAQ metabolic equivalent (MET) 9 and the modified Bruce protocol was used for individuals having VSAQ MET 6. Individuals having intermediate VSAQ MET 7/8 were assigned to Bruce protocol when step-test criteria were fulfilled; otherwise they were assigned to the modified protocol. The protocol began with a 1-minute warm-up, during which participants walked comfortably at selfpaced speed and at 0% grade. The workload was then increased according to the Bruce or modified Bruce protocol, respectively.21 Oxygen uptake was considered maximal if any two of the following criteria were met: (a) respiratory exchange ratio 1.1; (b) a heart rate at or near agepredicted peak (220-age 10 beats/min); and (c) when further increase in workload did not result in a significant rise in oxygen uptake (60 years, female gender, BMI >29 kgm2, VSAQ score
