Background Aerobic capacity tests are important to evaluate exercise programs and to encourage individuals to a physically active lifestyle. Maximum aerobic tests in a laboratory setting are expensive and not always feasible for people with rheumatoid arthritis (RA) (1). Submaximal tests, if proven valid and reliable, could thus be an alternative to maximum tests. The Åstrand submaximal bicycle test has been extensively used in clinic and research in people with RA, but never tested for validity and reliability in this population (2).
Objectives To test the validity of the Åstrand submaximal test for estimation of aerobic capacity, by exploring the correlation with the measured maximum oxygen uptake (measured VO2max) in people with RA.
Methods Twenty seven subjects (81% female), mean (SD) age 62 (8.1) years, diagnosed with RA since 17.9 (11.7) years, activity limitation according to the Stanford Health Assessment Questionnaire 0.412 (0.42) and Disease Activity Score 28 2.4 (0.42), participated in the study. The subjects performed the Åstrand test and the measured VO2max test (Alpha version 4.5, Jaeger, KFA-2028-01) at the same test occasion. According to the Åstrand-nomograms the VO2max was estimated using heart rate (HR) measurements from a single stage and adjusted for age or for maximal HR.
Results The correlation between VO2max estimated by the Åstrand test corrected for age and the measured VO2max test was r =0.82 (p<0.001) when expressed in l/min and r =0.68 (p<0.001) when expressed in ml kg–1 min–1, No systematic over- or underestimations were present although a majority of cases were underestimated. The correlation between VO2max estimated by the Åstrand test corrected for maximum HR and the measured VO2max test was r =0.82 (p<0.001) when expressed in l/min and r =0.65 (p<0.001) when expressed in ml kg–1 min–1. No systematic over- or under estimations were present.
Conclusions The Åstrand test could be considered a valid instrument to estimate VO2max in physically active people with RA that are able to perform a submaximal cycle test during six minutes
Eurenius E, Brodin N, Opava CH. Clinical applicability of of two tests of aerobic fitness in patients with rheumatoid arthritis. Adv Physiother 2007(9):97-104.
Astrand PO, Ryhming I. A nomogram for calculation of aerobic capacity (physical fitness) from pulse rate during sub-maximal work. J Appl Physiol. 1954;7(2):218-21.
Acknowledgements The Swedish Rheumatism Association, the National Postgraduate School of Health Care Sciences at Karolinska Institutet.
Disclosure of Interest None declared