Associations between walking time, quadriceps muscle strength and cardiovascular capacity in patients with rheumatoid arthritis and ankylosing spondylitis.

The aim of this study was to examine whether there are any associations between walking time, quadriceps muscle strength and cardiovascular capacity in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Thirty-one patients with RA and 26 patients with AS belonging to Steinbrocker's functional class I-II were examined. Cardiovascular capacity was calculated from the expired air during a bicycle test and quadriceps muscle strength by the peak torque from an isokinetic dynamometer test. Walking time was the time it took to walk a distance of 160 m on a flat floor and to climb up and down a staircase. In patients with RA, flat floor walking and stair climbing times correlated inversely with quadriceps muscle strength and cardiovascular capacity. Similar results were seen in patients with AS, although the association between cardiovascular capacity and stair-climbing time was not statistically significant. Multiple regression analysis was performed for all patients with quadriceps muscle strength and cardiovascular capacity applied as independent variables in two separate models. Cardiovascular capacity explained 32% and quadriceps muscle strength 21% of the variance in flat floor walking time. Quadriceps muscle strength, together with diagnosis and age, explained 38% of the variance in stair-climbing time, and cardiovascular capacity together with age and pain explained 36% of the variance. In conclusion, in spite of cardiovascular capacity and quadriceps muscle strength being associated with walking times, the findings suggest that they play only a modest role in explaining rapid walking on flat floor and in stairs.