Scandinavian Journal of Clinical & Laboratory Investigation, 2014; 74: 722–724
TECHNICAL NOTE
Comparison of COSMED’S FitMate™ and K4b2 metabolic systems reliability during graded cycling exercise
JEANICK BRISSWALTER1 & MARCUS P. TARTARUGA2 1University
of Nice Sophia Antipolis, Laboratory of Human Motricity, Education Sport and Health, Nice, France, and 2Midwest State University of Paraná, Biomechanics Laboratory, Guarapuava, Brazil Abstract This study compared the reliability of the Cosmed FitMate™ and K4b2 metabolic systems during light to heavy steady state exercise. Expired gas, ventilation were recorded in 50 subjects, using in a random order among four sessions, either the FitMate™ or the Cosmed K4b2. No differences in oxygen consumption were observed between the two systems whatever the intensity. Intraclass correlation were high for both analyzers (respectively for the FitMate™ system and the Cosmed K4b2; ICC: 0.76–0.88 vs. 0.88–0.95). The FitMate™ metabolic system could be a useful reliable and easy-to-use metabolic system in energy expenditure measurement. Key Words: Methodology, energy expenditure, reliability, oxygen consumption, exercise test
Introduction Measurement of oxygen consumption (VO2) is used in laboratory testing of athletes, assessment of the metabolic demand in sports events or in evaluation of therapeutic interventions. Metabolic measurement systems require expensive laboratory equipment that often lack portability. As a result the ability to measure individuals during activities is not only costly but difficult to accomplish in realworld settings. Technological advances have led to the development of portable indirect calorimeters, which are lightweight, battery operated, and capable to measure VO2 in a variety of settings. Therefore there has been a trend towards the use of portable breath-by-breath analyzers, in an attempt to link respiratory variables to metabolic events in the muscle and several portable breath by breath analyzers have been validated [1,2]. However these analyzers are often costly and the faster measurements needed for each inhalation creates possibilities of measurement error that requires attention to record and interpret data [3]. Nieman et al. [4,5], have validated a new small, and easy-to-use metabolic system the FitMate™
(Cosmed, Rome, Italy) compared with the Douglas bag system in measuring VO2 and ventilation (VE) during a graded exercise. One characteristic of this analyzer is that it does not includes a CO2 analyzer but relies on a software paradigm that ramps the respiratory exchange ratio (RER) between 0.8 and 1.2 based on the increase in heart rate. Results from the Nieman et al. studies [4,5] indicate that this analyzer accurately measures oxygen consumption during graded exercise. These studies using a comparison method addressed the first main considerations for gas analyzers that need to be valid. Secondly, information on the reliability of the method is necessary. Reliability is defined as ‘the amount of (test-retest) measurement error that has been deemed acceptable for the effective practical use of a measurement tool’. Yet, reliability studies have not yet been conducted with the FitMate™ for different intensities. The purpose of this study was to assess the reliability of the FitMate™ metabolic system and to compare its reliability with the previously studied portable breath-by-breath analyzers Cosmed K4b2 (Cosmed, Rome, Italy).
Correspondence: Jeanick Brisswalter, University of Nice Sophia Antipolis, Laboratory of Human Motricity, Education Sport and Health, BP 3259, 06205 Nice, France. Tel: ⫹ 33 631 792717. Fax: ⫹ 33 492 296549. E-mail: [email protected] (Received 29 January 2014 ; accepted 30 May 2014 ) ISSN 0036-5513 print/ISSN 1502-7686 online © 2014 Informa Healthcare DOI: 10.3109/00365513.2014.930711
COSMED’S FitMate™ reliability Table I. Characteristics of subjects.
Age (years) Height (m) Weight (kg) Maximal oxygen consumption (l. min⫺1) Power at ventilatory threshold (watts)
Male
Female
20.3 ⫾ 2.1 1.78 ⫾ 0.0 70.1 ⫾ 5.2 3.8 ⫾ 0.3
20.6 ⫾ 2.2 1.67 ⫾ 0.1 60.6 ⫾ 3.4 2.7 ⫾ 0.2
240 ⫾ 30
180 ⫾ 20
723
60 s recovery at the following intensities [6]: light exercise (VT ⫺ 20%), moderate exercise (VT) and heavy exercise (VT ⫹ 20%). During each session expired gas, and ventilation were recorded using, in a random order among the four sessions, either the FitMate™ metabolic system or the Cosmed K4b2 analyzer and heart rate (HR) was recorded with a RS800CX (Polar, Kempele, Finland). Values from the last 3 min of each stage were used for analysis. During testing all participants refrained from any strenuous training exercise.
Mean (⫾ SD) values of 30 males and 20 females are shown.
Methods
Statistical analysis
Subjects University students in physical education including 30 males and 20 females participated in this study (Table I). All subjects had to be free from present or past neuromuscular and metabolic conditions that could affect the recorded parameters. All the procedures were in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 1983. The University local ethics committee approved the study before its initiation and all subjects gave their informed written consent before participation.
VO2, VE and HR were compared amongst the four session and for each intensity by a two-way repeated measures ANOVA (session ⫻ analyzer). A NewmanKeuls post-hoc test was used for multiple comparisons to identify differences between sessions or analyzers. To examine the reliability of the measurements an Intra-class correlation coefficient (ICC, R) and a coefficient of variation (CV) were calculated for each dependent variable. The magnitude of reliability was judged by the R values of ICC as recommended by Munro [7]: 0–0.25: little, 0.26–0.49: low, 0.50–0.69: moderate, 0.70–0.89: high, and 0.9–1.0: very high. The significance level was set at p ⬍ 0.05.
Study design
Results
The study was divided into two phases. During the first phase, subjects were familiarized with procedures to be used, and a preliminary test was performed to determine V02max and power at the first ventilatory threshold (VT), using the Cosmed K4b2 analyzer. This test began with a warm-up lasting 6 min at 100 W, after which the power output was increased by 25 W each minute until the subjects were exhausted. During the second phase, four sessions of cycling were conducted at the same period of the day with at least 2 days between sessions. Each session was composed by a graded exercise including three stages, 6 min in length and interspersed with a
Oxygen consumption and ventilation For each intensity no significant differences were observed in VO2 and VE between the two systems of measurement or between sessions (Table II). The reliability of VO2 using the FitMate™ system was high from light to heavy intensities (ICC: 0.76–0.88, CV: 3.45–4.66%) whereas reliability was high to very high for VE for all intensities (ICC: 0.85–0.93; CV: 1.6– 2.6%). Using the Cosmed K4b2 analyzer reliability of VO2 and VE was high to very high for all intensities (for VO2 and VE [ICC: 0.88–0.95; CV: 1.78–2.36%] and [ICC: 0.82–0.91; CV: 2.0–2.8%]).
Table II. Values for oxygen consumption (VO2) minute ventilation (VE) and heart rate (HR) during sessions. (mean ⫾ SD, n ⫽ 46). Reproducibility determined as an Intraclass correlation R (ICC) and coefficient of variation (CV in %) for the two sessions with each analyzer. FitMate™
VO2 l.min⫺1 VE l.min⫺1 HR bpm
Cosmed K4b2
intensity
Session 1
Session 2
ICC
CV %
Session 1
Session 2
ICC
CV %
light moderate Heavy light moderate Heavy light moderate Heavy
1.75 ⫾ 0.21 2.14 ⫾ 0.24 2.64 ⫾ 0.22 34.8 ⫾ 5.2 41.6 ⫾ 6 65.3 ⫾ 7.5 111 ⫾ 12 139 ⫾ 8 159 ⫾ 11
1.67 ⫾ 0.18 2.04 ⫾ 0.23 2.82 ⫾ 0.26 33.6 ⫾ 4.8 43.1 ⫾ 5.5 66.8 ⫾ 6.4 113 ⫾ 11 140 ⫾ 10 157 ⫾ 10
0.88 0.86 0.76 0.85 0.93 0.88 0.97 0.97 0.92
4.66 3.72 3.45 2.6 2.5 1.6 1.3 0.6 0.9
1.58 ⫾ 0.24 2.19 ⫾ 0.18 2.78 ⫾ 0.31 35.5 ⫾ 6.1 42.9 ⫾ 5.7 66.2 ⫾ 8.2 109 ⫾ 10 141 ⫾ 9 158 ⫾ 12
1.64 ⫾ 0.24 2.12 ⫾ 0.17 2.72 ⫾ 0.27 34.3 ⫾ 5.5 44.6 ⫾ 4.9 68.1 ⫾ 4.8 111 ⫾ 8 143 ⫾ 11 155 ⫾ 11
0.95 0.93 0.88 0.91 0.88 0.82 0.97 0.95 0.90
2.36 2.41 1.78 2.2 2.8 2.0 1.3 1.1 1.6
724
J. Brisswalter & M. P. Tartaruga
Heart rate Heart rate values showed a high reliability among session whatever the speed with ICC values ranging from 0.90–0.97 and CV values from 0.6–1.6%.
Discussion The first finding of this study indicated that VO2 measurements using the FitMate™ system were not statistically different compared to those obtained with the Cosmed K4b2 (i.e. reference system) for light to heavy cycling exercises. The second main finding of this study was that reliability values for the FitMate™ system were high for light to heavy intensity and could be compared with those recorded with the Cosmed K4b2. Reliability values for the Cosmed K4b2 ranging from 0.88–0.95 were in agreement with studies indicating high to very high reliability with ICC ranging from 0.7–0.97 [8–10]. ICC values for the FitMate™ system ranging from 0.76–0.88 for VO2 were slightly lower than those reported for the Cosmed K4b2 but similar to those reported for other systems [2,9]. Whatever the intensity, CV values were higher for VO2 between K4b2 and FitMate™ systems but were not different for VE. Nevertheless CV values calculated in this study were all lower than the 10% accepted as the minimal criteria of reliability [2,11]. For example, during light exercise a CV of 4.6% for VO2 with the FitMate™ system would indicate that a person who expanded 25 mL.kg⫺1.min⫺1 might vary by 1.1 mL.kg-1.min-1 whereas it varied by 0.6 mL.kg⫺1. min⫺1 with the Cosmed K4b2. Results reporting high relibility for light to moderate intensities indicated that the FitMate™ metabolic system could be useful for all measurement of expenditure of locomotion, where validity of the measure depends on the submaximal exercise, such as the evaluation of the efficiency of locomotion for athletes after technical or training strategies [12] and also intervention outcomes with patients undergoing rehabilitation [13], For heavy intensities, even if reliability values were slightly lower than for the Cosmed K4b2, no significant differences were recorded in VO2 values between the two analyzers. This results is in agreement with the study by Nieman et al. [5] indicating that even for intensities above ventilatory threshold,
the FitMate™ system could allow the measure of VO2max. Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper. The authors have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
References [1] McLaughlin JE, King GA, Howley ET, Bassett DR Jr, Ainsworth BE. Validation of the COSMED K4 b2 portable metabolic system. Int J Sports Med 2001;22:280–4. [2] Blessinger J, Sawyer B, Davis C, Irving BA, Weltman A, Gaesser G. Reliability of the VmaxST portable metabolic measurement system. Int J Sports Med 2009;30:22–6. [3] Myers J, Walsh D, Sullivan M, Froelicher V. Effect of sampling on variability and plateau in oxygen uptake. J Appl Physiol 1990;68:404–10. [4] Nieman DC, Austin MD, Benezra L, Pearce S, McInnis T, Unick J, Gross SJ. Validation of Cosmed’s FitMate in measuring oxygen consumption and estimating resting metabolic rate. Res Sports Med 2006;14:89–96. [5] Nieman DC, Lasasso H, Austin MD, Pearce S, McInnis T, Unick J. Validation of Cosmed’s FitMate in measuring exercise metabolism. Res Sports Med 2007;15:67–75. [6] Whipp BJ. The slow component of O2 uptake kinetics during heavy exercise. Med Sci Sports Exerc 1994;26:1319–26. [7] Munro BH. Statistical analysis: understanding the results. Clin Nurse Special 1989;3:113. [8] Duffield R, Dawson B, Pinnington HC, Wong P. Accuracy and reliability of a Cosmed K4b2 portable gas analysis system. J Sci Med Sport 2004;7:11–22. [9] Schrack JA, Simonsick EM, Ferrucci L. Comparison of the Cosmed K4b(2) portable metabolic system in measuring steady-state walking energy expenditure. PloS One 2010; 5:e9292. [10] Lothian F, Farrally MR, Mahoney C. Validity and reliability of the Cosmed K2 to measure oxygen uptake. Can J Appl Physiol 1993;18:197–206. [11] Crouter SE, Antczak A, Hudak JR, DellaValle DM, Haas JD. Accuracy and reliability of the ParvoMedics TrueOne 2400 and MedGraphics VO2000 metabolic systems. Eur J Appl Physiol 2006;98:139–51. [12] Delextrat A, Tricot V, Bernard T, Vercruyssen F, Hausswirth C, Brisswalter J. Drafting during swimming improves efficiency during subsequent cycling. Med Sci Sports Exerc 2003;35:1612–9. [13] Faggiano P, D’Aloia A, Gualeni A, Lavatelli A, Giordano A. Assessment of oxygen uptake during the 6-minute walking test in patients with heart failure: preliminary experience with a portable device. Am Heart J 1997;134:203–6.
Copyright of Scandinavian Journal of Clinical & Laboratory Investigation is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
TECHNICAL NOTE
Comparison of COSMED’S FitMate™ and K4b2 metabolic systems reliability during graded cycling exercise
JEANICK BRISSWALTER1 & MARCUS P. TARTARUGA2 1University
of Nice Sophia Antipolis, Laboratory of Human Motricity, Education Sport and Health, Nice, France, and 2Midwest State University of Paraná, Biomechanics Laboratory, Guarapuava, Brazil Abstract This study compared the reliability of the Cosmed FitMate™ and K4b2 metabolic systems during light to heavy steady state exercise. Expired gas, ventilation were recorded in 50 subjects, using in a random order among four sessions, either the FitMate™ or the Cosmed K4b2. No differences in oxygen consumption were observed between the two systems whatever the intensity. Intraclass correlation were high for both analyzers (respectively for the FitMate™ system and the Cosmed K4b2; ICC: 0.76–0.88 vs. 0.88–0.95). The FitMate™ metabolic system could be a useful reliable and easy-to-use metabolic system in energy expenditure measurement. Key Words: Methodology, energy expenditure, reliability, oxygen consumption, exercise test
Introduction Measurement of oxygen consumption (VO2) is used in laboratory testing of athletes, assessment of the metabolic demand in sports events or in evaluation of therapeutic interventions. Metabolic measurement systems require expensive laboratory equipment that often lack portability. As a result the ability to measure individuals during activities is not only costly but difficult to accomplish in realworld settings. Technological advances have led to the development of portable indirect calorimeters, which are lightweight, battery operated, and capable to measure VO2 in a variety of settings. Therefore there has been a trend towards the use of portable breath-by-breath analyzers, in an attempt to link respiratory variables to metabolic events in the muscle and several portable breath by breath analyzers have been validated [1,2]. However these analyzers are often costly and the faster measurements needed for each inhalation creates possibilities of measurement error that requires attention to record and interpret data [3]. Nieman et al. [4,5], have validated a new small, and easy-to-use metabolic system the FitMate™
(Cosmed, Rome, Italy) compared with the Douglas bag system in measuring VO2 and ventilation (VE) during a graded exercise. One characteristic of this analyzer is that it does not includes a CO2 analyzer but relies on a software paradigm that ramps the respiratory exchange ratio (RER) between 0.8 and 1.2 based on the increase in heart rate. Results from the Nieman et al. studies [4,5] indicate that this analyzer accurately measures oxygen consumption during graded exercise. These studies using a comparison method addressed the first main considerations for gas analyzers that need to be valid. Secondly, information on the reliability of the method is necessary. Reliability is defined as ‘the amount of (test-retest) measurement error that has been deemed acceptable for the effective practical use of a measurement tool’. Yet, reliability studies have not yet been conducted with the FitMate™ for different intensities. The purpose of this study was to assess the reliability of the FitMate™ metabolic system and to compare its reliability with the previously studied portable breath-by-breath analyzers Cosmed K4b2 (Cosmed, Rome, Italy).
Correspondence: Jeanick Brisswalter, University of Nice Sophia Antipolis, Laboratory of Human Motricity, Education Sport and Health, BP 3259, 06205 Nice, France. Tel: ⫹ 33 631 792717. Fax: ⫹ 33 492 296549. E-mail: [email protected] (Received 29 January 2014 ; accepted 30 May 2014 ) ISSN 0036-5513 print/ISSN 1502-7686 online © 2014 Informa Healthcare DOI: 10.3109/00365513.2014.930711
COSMED’S FitMate™ reliability Table I. Characteristics of subjects.
Age (years) Height (m) Weight (kg) Maximal oxygen consumption (l. min⫺1) Power at ventilatory threshold (watts)
Male
Female
20.3 ⫾ 2.1 1.78 ⫾ 0.0 70.1 ⫾ 5.2 3.8 ⫾ 0.3
20.6 ⫾ 2.2 1.67 ⫾ 0.1 60.6 ⫾ 3.4 2.7 ⫾ 0.2
240 ⫾ 30
180 ⫾ 20
723
60 s recovery at the following intensities [6]: light exercise (VT ⫺ 20%), moderate exercise (VT) and heavy exercise (VT ⫹ 20%). During each session expired gas, and ventilation were recorded using, in a random order among the four sessions, either the FitMate™ metabolic system or the Cosmed K4b2 analyzer and heart rate (HR) was recorded with a RS800CX (Polar, Kempele, Finland). Values from the last 3 min of each stage were used for analysis. During testing all participants refrained from any strenuous training exercise.
Mean (⫾ SD) values of 30 males and 20 females are shown.
Methods
Statistical analysis
Subjects University students in physical education including 30 males and 20 females participated in this study (Table I). All subjects had to be free from present or past neuromuscular and metabolic conditions that could affect the recorded parameters. All the procedures were in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 1983. The University local ethics committee approved the study before its initiation and all subjects gave their informed written consent before participation.
VO2, VE and HR were compared amongst the four session and for each intensity by a two-way repeated measures ANOVA (session ⫻ analyzer). A NewmanKeuls post-hoc test was used for multiple comparisons to identify differences between sessions or analyzers. To examine the reliability of the measurements an Intra-class correlation coefficient (ICC, R) and a coefficient of variation (CV) were calculated for each dependent variable. The magnitude of reliability was judged by the R values of ICC as recommended by Munro [7]: 0–0.25: little, 0.26–0.49: low, 0.50–0.69: moderate, 0.70–0.89: high, and 0.9–1.0: very high. The significance level was set at p ⬍ 0.05.
Study design
Results
The study was divided into two phases. During the first phase, subjects were familiarized with procedures to be used, and a preliminary test was performed to determine V02max and power at the first ventilatory threshold (VT), using the Cosmed K4b2 analyzer. This test began with a warm-up lasting 6 min at 100 W, after which the power output was increased by 25 W each minute until the subjects were exhausted. During the second phase, four sessions of cycling were conducted at the same period of the day with at least 2 days between sessions. Each session was composed by a graded exercise including three stages, 6 min in length and interspersed with a
Oxygen consumption and ventilation For each intensity no significant differences were observed in VO2 and VE between the two systems of measurement or between sessions (Table II). The reliability of VO2 using the FitMate™ system was high from light to heavy intensities (ICC: 0.76–0.88, CV: 3.45–4.66%) whereas reliability was high to very high for VE for all intensities (ICC: 0.85–0.93; CV: 1.6– 2.6%). Using the Cosmed K4b2 analyzer reliability of VO2 and VE was high to very high for all intensities (for VO2 and VE [ICC: 0.88–0.95; CV: 1.78–2.36%] and [ICC: 0.82–0.91; CV: 2.0–2.8%]).
Table II. Values for oxygen consumption (VO2) minute ventilation (VE) and heart rate (HR) during sessions. (mean ⫾ SD, n ⫽ 46). Reproducibility determined as an Intraclass correlation R (ICC) and coefficient of variation (CV in %) for the two sessions with each analyzer. FitMate™
VO2 l.min⫺1 VE l.min⫺1 HR bpm
Cosmed K4b2
intensity
Session 1
Session 2
ICC
CV %
Session 1
Session 2
ICC
CV %
light moderate Heavy light moderate Heavy light moderate Heavy
1.75 ⫾ 0.21 2.14 ⫾ 0.24 2.64 ⫾ 0.22 34.8 ⫾ 5.2 41.6 ⫾ 6 65.3 ⫾ 7.5 111 ⫾ 12 139 ⫾ 8 159 ⫾ 11
1.67 ⫾ 0.18 2.04 ⫾ 0.23 2.82 ⫾ 0.26 33.6 ⫾ 4.8 43.1 ⫾ 5.5 66.8 ⫾ 6.4 113 ⫾ 11 140 ⫾ 10 157 ⫾ 10
0.88 0.86 0.76 0.85 0.93 0.88 0.97 0.97 0.92
4.66 3.72 3.45 2.6 2.5 1.6 1.3 0.6 0.9
1.58 ⫾ 0.24 2.19 ⫾ 0.18 2.78 ⫾ 0.31 35.5 ⫾ 6.1 42.9 ⫾ 5.7 66.2 ⫾ 8.2 109 ⫾ 10 141 ⫾ 9 158 ⫾ 12
1.64 ⫾ 0.24 2.12 ⫾ 0.17 2.72 ⫾ 0.27 34.3 ⫾ 5.5 44.6 ⫾ 4.9 68.1 ⫾ 4.8 111 ⫾ 8 143 ⫾ 11 155 ⫾ 11
0.95 0.93 0.88 0.91 0.88 0.82 0.97 0.95 0.90
2.36 2.41 1.78 2.2 2.8 2.0 1.3 1.1 1.6
724
J. Brisswalter & M. P. Tartaruga
Heart rate Heart rate values showed a high reliability among session whatever the speed with ICC values ranging from 0.90–0.97 and CV values from 0.6–1.6%.
Discussion The first finding of this study indicated that VO2 measurements using the FitMate™ system were not statistically different compared to those obtained with the Cosmed K4b2 (i.e. reference system) for light to heavy cycling exercises. The second main finding of this study was that reliability values for the FitMate™ system were high for light to heavy intensity and could be compared with those recorded with the Cosmed K4b2. Reliability values for the Cosmed K4b2 ranging from 0.88–0.95 were in agreement with studies indicating high to very high reliability with ICC ranging from 0.7–0.97 [8–10]. ICC values for the FitMate™ system ranging from 0.76–0.88 for VO2 were slightly lower than those reported for the Cosmed K4b2 but similar to those reported for other systems [2,9]. Whatever the intensity, CV values were higher for VO2 between K4b2 and FitMate™ systems but were not different for VE. Nevertheless CV values calculated in this study were all lower than the 10% accepted as the minimal criteria of reliability [2,11]. For example, during light exercise a CV of 4.6% for VO2 with the FitMate™ system would indicate that a person who expanded 25 mL.kg⫺1.min⫺1 might vary by 1.1 mL.kg-1.min-1 whereas it varied by 0.6 mL.kg⫺1. min⫺1 with the Cosmed K4b2. Results reporting high relibility for light to moderate intensities indicated that the FitMate™ metabolic system could be useful for all measurement of expenditure of locomotion, where validity of the measure depends on the submaximal exercise, such as the evaluation of the efficiency of locomotion for athletes after technical or training strategies [12] and also intervention outcomes with patients undergoing rehabilitation [13], For heavy intensities, even if reliability values were slightly lower than for the Cosmed K4b2, no significant differences were recorded in VO2 values between the two analyzers. This results is in agreement with the study by Nieman et al. [5] indicating that even for intensities above ventilatory threshold,
the FitMate™ system could allow the measure of VO2max. Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper. The authors have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
References [1] McLaughlin JE, King GA, Howley ET, Bassett DR Jr, Ainsworth BE. Validation of the COSMED K4 b2 portable metabolic system. Int J Sports Med 2001;22:280–4. [2] Blessinger J, Sawyer B, Davis C, Irving BA, Weltman A, Gaesser G. Reliability of the VmaxST portable metabolic measurement system. Int J Sports Med 2009;30:22–6. [3] Myers J, Walsh D, Sullivan M, Froelicher V. Effect of sampling on variability and plateau in oxygen uptake. J Appl Physiol 1990;68:404–10. [4] Nieman DC, Austin MD, Benezra L, Pearce S, McInnis T, Unick J, Gross SJ. Validation of Cosmed’s FitMate in measuring oxygen consumption and estimating resting metabolic rate. Res Sports Med 2006;14:89–96. [5] Nieman DC, Lasasso H, Austin MD, Pearce S, McInnis T, Unick J. Validation of Cosmed’s FitMate in measuring exercise metabolism. Res Sports Med 2007;15:67–75. [6] Whipp BJ. The slow component of O2 uptake kinetics during heavy exercise. Med Sci Sports Exerc 1994;26:1319–26. [7] Munro BH. Statistical analysis: understanding the results. Clin Nurse Special 1989;3:113. [8] Duffield R, Dawson B, Pinnington HC, Wong P. Accuracy and reliability of a Cosmed K4b2 portable gas analysis system. J Sci Med Sport 2004;7:11–22. [9] Schrack JA, Simonsick EM, Ferrucci L. Comparison of the Cosmed K4b(2) portable metabolic system in measuring steady-state walking energy expenditure. PloS One 2010; 5:e9292. [10] Lothian F, Farrally MR, Mahoney C. Validity and reliability of the Cosmed K2 to measure oxygen uptake. Can J Appl Physiol 1993;18:197–206. [11] Crouter SE, Antczak A, Hudak JR, DellaValle DM, Haas JD. Accuracy and reliability of the ParvoMedics TrueOne 2400 and MedGraphics VO2000 metabolic systems. Eur J Appl Physiol 2006;98:139–51. [12] Delextrat A, Tricot V, Bernard T, Vercruyssen F, Hausswirth C, Brisswalter J. Drafting during swimming improves efficiency during subsequent cycling. Med Sci Sports Exerc 2003;35:1612–9. [13] Faggiano P, D’Aloia A, Gualeni A, Lavatelli A, Giordano A. Assessment of oxygen uptake during the 6-minute walking test in patients with heart failure: preliminary experience with a portable device. Am Heart J 1997;134:203–6.
Copyright of Scandinavian Journal of Clinical & Laboratory Investigation is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
