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Davidson P, Trinh H, Vekki S, Müller P. Surrogate Modelling for Oxygen Uptake Prediction Using LSTM Neural Network. SENSORS (BASEL, SWITZERLAND) 2023; 23:2249. [PMID: 36850848 PMCID: PMC9964573 DOI: 10.3390/s23042249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 02/13/2023] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
Oxygen uptake (V˙O2) is an important metric in any exercise test including walking and running. It can be measured using portable spirometers or metabolic analyzers. Those devices are, however, not suitable for constant use by consumers due to their costs, difficulty of operation and their intervening in the physical integrity of their users. Therefore, it is important to develop approaches for the indirect estimation of V˙O2-based measurements of motion parameters, heart rate data and application-specific measurements from consumer-grade sensors. Typically, these approaches are based on linear regression models or neural networks. This study investigates how motion data contribute to V˙O2 estimation accuracy during unconstrained running and walking. The results suggest that a long short term memory (LSTM) neural network can predict oxygen consumption with an accuracy of 2.49 mL/min/kg (95% limits of agreement) based only on speed, speed change, cadence and vertical oscillation measurements from an inertial navigation system combined with a Global Positioning System (INS/GPS) device developed by our group, worn on the torso. Combining motion data and heart rate data can significantly improve the V˙O2 estimation resulting in approximately 1.7-1.9 times smaller prediction errors than using only motion or heart rate data.
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Affiliation(s)
- Pavel Davidson
- Faculty of Information Technology and Communication Sciences, Tampere University, 33720 Tampere, Finland
| | - Huy Trinh
- Faculty of Information Technology and Communication Sciences, Tampere University, 33720 Tampere, Finland
| | - Sakari Vekki
- Faculty of Sport and Health Sciences, University of Jyväskylä, Seminaarinkatu 15, 40014 Jyväskylän yliopisto, Finland
| | - Philipp Müller
- Faculty of Information Technology and Communication Sciences, Tampere University, 33720 Tampere, Finland
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Okamoto T, Kobayashi R, Hashimoto Y, Kikuchi N, Ogoh S. Is individual day-to-day variation of arterial stiffness associated with variation of maximal aerobic performance? BMC Sports Sci Med Rehabil 2021; 13:4. [PMID: 33422135 PMCID: PMC7797097 DOI: 10.1186/s13102-021-00231-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 01/01/2021] [Indexed: 11/10/2022]
Abstract
Background Maximal aerobic capacity, e.g. maximal oxygen uptake (V̇O2max), is not constant, and it has a time-dependent variation based on the condition of individual. On the other hand, arterial properties play an important role in determining aerobic performance, and lower arterial stiffness is associated with higher cardiorespiratory fitness levels. This study examined whether individual variations in maximal aerobic performance are associated with arterial stiffness. Methods Twenty-four (mean age, 19.8 ± 0.2 y) and 10 (mean age, 21.2 ± 0.2 y) recreationally active young men and women participated in Experiment 1 (Ex1) and in Experiment 2 (Ex2), respectively. Aerobic performance was assessed using a graded power test (Ex1) or a 1500-m time trial (Ex2). Simultaneously, brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial stiffness in both Ex1 and Ex2 before the exercise trials. In both experiments, subjects returned for measurement of baPWV and V̇O2max or 1500-m time trial at 1 month after first measurements. Results No significant differences in mean baPWV, V̇O2max or 1500-m run time were seen between first and second visits. Mean baPWV was significantly lower on days when participants showed higher V̇O2max or better 1500-m run time (P = 0.001 each) than on days when participants showed lower V̇O2max or worse 1500-m run time. In addition, a significant relationship was seen between individual changes in baPWV from first to second visits and changes in V̇O2max (P=0.0001) or 1500-m run time (P=0.04). Conclusion These findings suggest that individual day-to-day variations in maximal aerobic performance are associated with variations in arterial stiffness. Supplementary Information The online version contains supplementary material available at 10.1186/s13102-021-00231-1.
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Affiliation(s)
- Takanobu Okamoto
- Department of Exercise Physiology, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508, Japan.
| | - Ryota Kobayashi
- Center for Fundamental Education, Teikyo University of Science, Tokyo, Japan
| | - Yuto Hashimoto
- Department of Exercise Physiology, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508, Japan
| | - Naoki Kikuchi
- Department of Training Science, Nippon Sport Science University, Tokyo, Japan
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Saitama, Japan
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d'Arbeloff T, Cooke M, Knodt AR, Sison M, Melzer TR, Ireland D, Poulton R, Ramrakha S, Moffitt TE, Caspi A, Hariri AR. Is cardiovascular fitness associated with structural brain integrity in midlife? Evidence from a population-representative birth cohort study. Aging (Albany NY) 2020; 12:20888-20914. [PMID: 33082296 PMCID: PMC7655208 DOI: 10.18632/aging.104112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 08/09/2020] [Indexed: 12/31/2022]
Abstract
Improving cardiovascular fitness may buffer against age-related cognitive decline and mitigate dementia risk by staving off brain atrophy. However, it is unclear if such effects reflect factors operating in childhood (neuroselection) or adulthood (neuroprotection). Using data from 807 members of the Dunedin Study, a population-representative birth cohort, we investigated associations between cardiovascular fitness and structural brain integrity at age 45, and the extent to which associations reflected possible neuroselection or neuroprotection by controlling for childhood IQ. Higher fitness, as indexed by VO2Max, was not associated with average cortical thickness, total surface area, or subcortical gray matter volume including the hippocampus. However, higher fitness was associated with thicker cortex in prefrontal and temporal regions as well as greater cerebellar gray matter volume. Higher fitness was also associated with decreased hippocampal fissure volume. These associations were unaffected by the inclusion of childhood IQ in analyses. In contrast, a higher rate of decline in cardiovascular fitness from 26 to 45 years was not robustly associated with structural brain integrity. Our findings are consistent with a neuroprotective account of adult cardiovascular fitness but suggest that effects are not uniformly observed across the brain and reflect contemporaneous fitness more so than decline over time.
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Affiliation(s)
- Tracy d'Arbeloff
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Megan Cooke
- Center for Addiction Medicine, Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - Annchen R Knodt
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Maria Sison
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Tracy R Melzer
- New Zealand Brain Research Institute, Christchurch, New Zealand
- Department of Medicine, University of Otago, Christchurch, New Zealand
| | - David Ireland
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, NZ
| | - Richie Poulton
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, NZ
| | - Sandhya Ramrakha
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, NZ
| | - Terrie E Moffitt
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
- Social, Genetic, and Developmental Psychiatry Research Centre, Institute of Psychiatry, Psychology, and Neuroscience, King’s College London, De Crespigny Park, Denmark Hill, London, UK
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27708, USA
- Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - Avshalom Caspi
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
- Social, Genetic, and Developmental Psychiatry Research Centre, Institute of Psychiatry, Psychology, and Neuroscience, King’s College London, De Crespigny Park, Denmark Hill, London, UK
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27708, USA
- Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - Ahmad R Hariri
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
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d'Arbeloff T. Cardiovascular fitness and structural brain integrity: an update on current evidence. GeroScience 2020; 42:1285-1306. [PMID: 32767221 PMCID: PMC7525918 DOI: 10.1007/s11357-020-00244-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/29/2020] [Indexed: 02/06/2023] Open
Abstract
An aging global population and accompanying increases in the prevalence of age-related disorders are leading to greater financial, social, and health burdens. Aging-related dementias are one such category of age-related disorders that are associated with progressive loss of physical and cognitive integrity. One proposed preventative measure against risk of aging-related dementia is improving cardiovascular fitness, which may help reverse or buffer age-related brain atrophy associated with worse aging-related outcomes and cognitive decline. However, research into the beneficial potential of cardiovascular fitness has suffered from extreme heterogeneity in study design methodology leading to a lack of cohesion in the field and undermining any potential causal evidence that may exist. In addition, cardiovascular fitness and exercise are often conflated, leading to a lack of clarity in results. Here, I review recent literature on cardiovascular fitness, brain structure, and aging with the following goals: (a) to disentangle and lay out recent findings specific to aging, cardiovascular fitness, and brain structure, and (b) to ascertain the extent to which causal evidence actually exists. I suggest that, while there is some preliminary evidence for a link between cardiovascular fitness and brain structure in older adults, more research is still needed before definitive causal conclusions can be drawn. I conclude with a discussion of existing gaps in the field and suggestions for how they may be addressed by future research.
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Affiliation(s)
- Tracy d'Arbeloff
- Laboratory of NeuroGenetics, Department of Psychology & Neuroscience, Duke University, Durham, NC, 27708, USA.
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Buresh R, Hornbuckle LM, Garrett D, Garber H, Woodward A. Associations between measures of health-related physical fitness and cardiometabolic risk factors in college students. JOURNAL OF AMERICAN COLLEGE HEALTH : J OF ACH 2018; 66:754-766. [PMID: 29405878 DOI: 10.1080/07448481.2018.1431910] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 11/17/2017] [Accepted: 01/14/2018] [Indexed: 06/07/2023]
Abstract
OBJECTIVE To determine the influence of health-related fitness on cardiometabolic risk factors in college students. PARTICIPANTS 75 traditional students (33 men and 42 women, 21.8±1.8 years old) at a university in southeastern U.S. METHODS Height, weight, waist circumference, body composition, blood pressure, lipids, glucose, insulin, c-reactive protein, and glucose tolerance were measured. Indices of insulin sensitivity were calculated. Aerobic and muscular fitness were measured. Regression and correlation analyses, and comparisons of cardiometabolic markers in low- vs high-fit participants were performed. RESULTS Men and women with low muscular fitness exhibited higher fasting insulin, and poorer insulin sensitivity index scores than those with high muscular fitness. In addition, women with high body fat percentage exhibited higher fasting and 2-hour insulin levels and lower insulin sensitivity index scores than those with low body fat percentages. CONCLUSIONS College students possessing low levels of health-related physical fitness exhibited less favorable cardiometabolic risk profiles.
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Affiliation(s)
- Robert Buresh
- a Department of Exercise Science and Sport Management , Kennesaw State University , Kennesaw , Georgia , USA
| | - Lyndsey M Hornbuckle
- b Department of Kinesiology , Recreation, and Sport Studies, University of Tennessee Knoxville , Knoxville , Tennessee , USA
| | - Danielle Garrett
- a Department of Exercise Science and Sport Management , Kennesaw State University , Kennesaw , Georgia , USA
| | - Hannah Garber
- a Department of Exercise Science and Sport Management , Kennesaw State University , Kennesaw , Georgia , USA
| | - Andrew Woodward
- a Department of Exercise Science and Sport Management , Kennesaw State University , Kennesaw , Georgia , USA
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Sartor F, Vernillo G, de Morree HM, Bonomi AG, La Torre A, Kubis HP, Veicsteinas A. Estimation of maximal oxygen uptake via submaximal exercise testing in sports, clinical, and home settings. Sports Med 2014; 43:865-73. [PMID: 23821468 DOI: 10.1007/s40279-013-0068-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Assessment of the functional capacity of the cardiovascular system is essential in sports medicine. For athletes, the maximal oxygen uptake [Formula: see text] provides valuable information about their aerobic power. In the clinical setting, the (VO(2max)) provides important diagnostic and prognostic information in several clinical populations, such as patients with coronary artery disease or heart failure. Likewise, VO(2max) assessment can be very important to evaluate fitness in asymptomatic adults. Although direct determination of [VO(2max) is the most accurate method, it requires a maximal level of exertion, which brings a higher risk of adverse events in individuals with an intermediate to high risk of cardiovascular problems. Estimation of VO(2max) during submaximal exercise testing can offer a precious alternative. Over the past decades, many protocols have been developed for this purpose. The present review gives an overview of these submaximal protocols and aims to facilitate appropriate test selection in sports, clinical, and home settings. Several factors must be considered when selecting a protocol: (i) The population being tested and its specific needs in terms of safety, supervision, and accuracy and repeatability of the VO(2max) estimation. (ii) The parameters upon which the prediction is based (e.g. heart rate, power output, rating of perceived exertion [RPE]), as well as the need for additional clinically relevant parameters (e.g. blood pressure, ECG). (iii) The appropriate test modality that should meet the above-mentioned requirements should also be in line with the functional mobility of the target population, and depends on the available equipment. In the sports setting, high repeatability is crucial to track training-induced seasonal changes. In the clinical setting, special attention must be paid to the test modality, because multiple physiological parameters often need to be measured during test execution. When estimating VO(2max), one has to be aware of the effects of medication on heart rate-based submaximal protocols. In the home setting, the submaximal protocols need to be accessible to users with a broad range of characteristics in terms of age, equipment, time available, and an absence of supervision. In this setting, the smart use of sensors such as accelerometers and heart rate monitors will result in protocol-free VO(2max) assessments. In conclusion, the need for a low-risk, low-cost, low-supervision, and objective evaluation of VO(2max) has brought about the development and the validation of a large number of submaximal exercise tests. It is of paramount importance to use these tests in the right context (sports, clinical, home), to consider the population in which they were developed, and to be aware of their limitations.
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Affiliation(s)
- Francesco Sartor
- Personal Health Solutions, Philips Research, High Tech Campus 34, P.O. Box WB61, 5656 AE Eindhoven, The Netherlands.
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Does a 3-min all-out test provide suitable measures of exercise intensity at the maximal lactate steady state or peak oxygen uptake for well-trained runners? Int J Sports Physiol Perform 2014; 9:805-10. [PMID: 24414148 DOI: 10.1123/ijspp.2013-0265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
PURPOSE To examine whether a 3-min all-out test can be used to obtain accurate values for the maximal lactate steady state (vMLSS) and/or peak oxygen uptake (VO2peak) of well-trained runners. METHODS The 15 male volunteers (25 ± 5 y, 181 ± 6 cm, 76 ± 7 kg, VO2peak 69.3 ± 9.5 mL · kg-1 · min-1) performed a ramp test, a 3-min all-out test, and several submaximal 30-min runs at constant paces of vEND (mean velocity during the last 30 s of the 3-min all-out test) itself and vEND +0.2, +0.1, -0.1, -0.2, -0.3, or -0.4 m/s. RESULTS vMLSS and vEND were correlated (r = .69, P = .004), although vMLSS was lower (mean difference: 0.26 ± 0.32 m/s, 95% CI -.44 to -.08 m/s, P = .007, effect size = 0.65). The VO2peak values derived from the ramp and 3-min all-out tests were not correlated (r = .41, P = .12), with a mean difference of 523 ± 1002 mL (95% CI 31 to 1077 mL). CONCLUSION A 3-min all-out test does not provide a suitable measure of vMLSS or VO2peak for well-trained runners.
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ONORATI PAOLO, MARTOLINI DARIO, VALLI GABRIELE, LAVENEZIANA PIERANTONIO, MARINELLI PAOLO, ANGELICI ELENA, PALANGE PAOLO. A Simplified Approach for the Estimation of the Ventilatory Compensation Point. Med Sci Sports Exerc 2012; 44:716-24. [DOI: 10.1249/mss.0b013e318237fb5f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bringard A, Layec G, Micallef JP, Bendahan D, Perrey S. Gas exchange measurements within a magnetic environment: validation of a new system. Respir Physiol Neurobiol 2012; 182:37-46. [PMID: 22366154 DOI: 10.1016/j.resp.2012.02.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 01/31/2012] [Accepted: 02/10/2012] [Indexed: 10/28/2022]
Abstract
Although simultaneous measurements of pulmonary oxygen uptake (VO2) and Phosphorus-31 magnetic resonance spectroscopy ((31)P MRS) is attractive to investigate muscular metabolism during exercise, the superconducting magnet requires the design of specific gas exchange analyser (GEA). Thus, this study aimed to assess the validity of a commercial GEA system (ZAN600) compatible with (31)P MRS measurements. Using nonmagnetic pneumotachograph and prolonged sampling line (from 2m, control condition, to 6.5m) did not alter the proper synchronisation between flow and gas concentration signals. Also, end-expiratory fraction of O2 (FETO2) and CO(2) (FETCO2), and finally the values of steady-state ventilation (V(E)), carbon dioxide production (VCO2) and VO2 kinetics during moderate knee-extension exercise were not significantly different between 2m and 6.5m conditions and between 6.5m condition inside and outside the magnet. These results showed that a prolonged sampling line used inside the superconducting magnet did not affect the accuracy of VO2 measurements of a commercial GEA system; the latter appears suitable for simultaneous measurements of VO2 and (31)P MRS.
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Affiliation(s)
- Aurélien Bringard
- Movement To Health, Montpellier-1 University, Euromov, 700 av du Pic Saint-Loup, 34090 Montpellier, France.
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Onorati P, Martolini D, Ora J, Valli G, Fedeli A, Palange P. Estimation of the exercise ventilatory compensation point by the analysis of the relationship between minute ventilation and heart rate. Eur J Appl Physiol 2008; 104:87-94. [DOI: 10.1007/s00421-008-0777-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2008] [Indexed: 11/28/2022]
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Stephens S, Singh-Grewal D, Bar-Or O, Beyene J, Cameron B, Leblanc CMA, Schneider R, Schneiderman-Walker J, Selvadurai H, Silverman E, Spiegel L, Tse SML, Wright V, Feldman BM. Reliability of exercise testing and functional activity questionnaires in children with juvenile arthritis. ACTA ACUST UNITED AC 2007; 57:1446-52. [DOI: 10.1002/art.23089] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Wisén AGM, Wohlfart B. Aerobic and functional capacity in a group of healthy women: reference values and repeatability. Clin Physiol Funct Imaging 2004; 24:341-51. [PMID: 15522043 DOI: 10.1111/j.1475-097x.2004.00576.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Twenty-five randomly selected, low or moderately fit and healthy women (22-44 years) rated their perceived physical capacity and performed an incremental cycle exercise test with respiratory gas analysis. The aerobic and functional capacity did not decrease with age. However, tauVo(2) increased with age. The mean value of the perceived physical capacity was 10 metabolic equivalents and that of Vo(2max) 2075 ml min(-1). The increasing anaerobic metabolism was determined at three points DX (where the rate of Vco(2) increase just exceeds the rate of Vo(2) increase), PX (where Vco(2)/Vo(2) = 1.0) and PQ (where ventilation increase disproportionately in relation to Vco(2)). The mean Vo(2) (% of Vo(2max)) at DX, PX and PQ were 1263 (63%), 1528 (73%) and 1620 (78%) ml min(-1), respectively. The mean value of deltaVo(2)/deltaW was 10.2 ml min(-1) W(-1) while that of tauVo(2) was 0.578 (age) + 15.6. Ten women performed a test and re-test on two consecutive days, and eight of these performed another re-test 4 weeks later. The repeatability was analysed and the variations were expressed as 2 SD of the differences between the tests. The variation was greater for the 4-week re-test than the day-to-day re-test regarding Vo(2max), o(2) at DX, PX and PQ, deltaVo(2)/deltaW and HR. The variation in Vo(2max), PX and deltaVo(2)/deltaW for the 4-week re-test was more than twice that of the previously reported 4-week variation for men. The considerable variation, especially for 4-week re-testing for women should be considered when evaluating the effects of exercise and rehabilitation.
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Affiliation(s)
- Anita G M Wisén
- Department of Clinical Physiology, Lund University Hospital, SE-221 85 Lund, Sweden.
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Wergel-Kolmert U, Wisén A, Wohlfart B. Repeatability of measurements of oxygen consumption, heart rate and Borg's scale in men during ergometer cycling. Clin Physiol Funct Imaging 2002; 22:261-5. [PMID: 12402448 DOI: 10.1046/j.1475-097x.2002.00428.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The coefficient of repeatability (COR), expressed as 2-SD of differences, was calculated between two measurements of oxygen consumption (V O2), heart rate (HR) and rating of perceived exertion (RPE) during ergometer cycling by men. The two sets of measurements were performed 5 to 6 weeks apart. Nineteen healthy men performed an incremental maximal exercise test on an ergometer cycle. The load started at 50 W and increased by 5 W 20 s-1 until exhaustion was reached. At 40% of the individual maximum load of the pretest, the load was kept constant for 4 min in order to reach steady state. Gas measurements were recorded continuously by computerized instrumentation. The HR was monitored with electrocardiography (ECG) and the perceived exertion was evaluated using Borg's scale. The COR of V O2 at sub-maximal load was 14% and at maximum load 11%. The values in absolute figures were 209 and 332 ml min-1. The corresponding COR of the HR was 16% at sub-maximum load and 6% at maximum load, and an evaluation of the perceived exertion yielded CORs in absolute values of 4.8 and 1.3, respectively. The COR for V O2, HR and ratings of perceived exertion when cycling on an ergometer cycle thus indicate a better agreement between the measurements at maximum load. The COR of the heart at sub-maximal loads must be kept in mind when using HR for estimation of V O2max. The reported findings should be considered when using tests on an ergometer cycle for evaluating exercise capacity.
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