Functional exercise capacity in patients with ankylosing spondylitis

This study aimed to measure the functional exercise capacity of patients with ankylosing spondylitis (AS) with the incremental shuttle walk test (ISWT), and to determine the factors associated with this test.

This cross-sectional study included 54 patients with AS (29 males, 25 females). The ISWT was performed to determine functional exercise capacity. The number of completed shuttles was recorded, and the total incremental shuttle walk distance (ISWD) was calculated. Disease activity was assessed with the Bath AS Disease Activity Index (BASDAI), physical functioning was assessed with the Bath AS Functional Index (BASFI), and spinal mobility was assessed with the Bath AS Mobility Index (BASMI). Upper body and core endurance were assessed by sit-up and push-up tests. Tests were performed in a single session in the order listed.

The mean ISWD of the patients was 462.41 ± 97.96 m, and the subjects reached 50.48% of the predicted ISWD. The ISWD of male subjects was significantly higher than that of females (p < .05). At the end of the test, male subjects reached 60.87% of the age-predicted maximal heart rate, and female subjects reached 55.25%. There was a significant positive moderate correlation between ISWD and height (r = 0.535, p < .01), sit-up test (r = 0.617, p < .01), and push-up test (r = 0.495, p < .01), while there was a negative weak correlation between BASFI (r = -0.344, p = .011) and BASMI (r = -0.280, p = .040).

The study showed that functional exercise capacity as assessed by the ISWT decreased in patients with AS. ISWT performance was associated with sex, height, functionality, spinal mobility, and muscular endurance.