Cardiopulmonary fitness is a function of lean mass, not total body weight: The DR's EXTRA study.
BACKGROUND
Division by total body weight is the usual way to standardise peak oxygen uptake (peak VO2) for body size. However, this method systematically underestimates cardiopulmonary fitness in obese individuals. Our aim was to analyse whether lean-mass is a better base for a body mass-independent standard of cardiopulmonary fitness.


METHODS
A population based sample of 578 men (body mass index (BMI) 19-47 kg/m(2)) and 592 women (BMI 16-49 kg/m(2)) 57-78 years of age. Peak VO2 was assessed by respiratory gas analysis during a maximal exercise test on a cycle ergometer. We studied the validity of the weight-ratio and the lean mass-ratio standards in a linear regression model.


RESULTS
The weight-ratio standard implies an increase of peak VO2 per additional kg body weight with 20.7 ml/min (95% confidence interval (CI): 20.3-21.1) in women and 26.9 ml/min (95% CI: 26.4-27.5) in men. The observed increase per kg is only 8.5 ml/min (95% CI: 6.5-10.5) in men and 10.4 ml/min (95% CI: 7.5-13.4) in women. For the lean mass-ratio standard expected and observed increases in peak VO2 per kg lean mass were 32.3 (95% CI: 31.8-32.9) and 34.6 (95% CI: 30.0-39.1) ml/min for women and 36.2 (95% CI: 35.6-36.8) and 37.3 (95% CI: 32.1-42.4) ml/min in men. The lean mass-ratio standard is a body mass-independent measure of cardiopulmonary fitness in 100% of women and 58% of men; corresponding values for the weight-ratio standard were 11% and 16%.


CONCLUSIONS
For comparisons of cardiopulmonary fitness across different categories of body mass, the lean mass-ratio standard should be used.
Kuopio Research Institute of Exercise Medicine, Finland Department of Public Health and Clinical Medicine, Umeå University, Sweden benno.krachler@envmed.umu.se.
Benno
B
Krachler
Kuopio Research Institute of Exercise Medicine, Finland Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Finland.
Kai
K
Savonen
Kuopio Research Institute of Exercise Medicine, Finland.
Pirjo
P
Komulainen
Kuopio Research Institute of Exercise Medicine, Finland.
Maija
M
Hassinen
Kuopio Research Institute of Exercise Medicine, Finland Institute of Biomedicine/Physiology, University of Eastern Finland, Finland.
Timo A
TA
Lakka
Kuopio Research Institute of Exercise Medicine, Finland Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Finland.
Rainer
R
Rauramaa
D000368:Aged; D000369:Aged, 80 and over; D001642:Bicycling; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D001944:Breath Tests; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005080:Exercise Test / Q000592:standards; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010809:Physical Fitness; D011237:Predictive Value of Tests; D011795:Surveys and Questionnaires
D010100:Oxygen
Exercise capacity; body composition; cardiopulmonary fitness; cardiorespiratory fitness; exercise physiology; exercise testing