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  1. Y. Acar1,
  2. N. Ilcin2,
  3. İ. Sari3,
  4. F. Onen3,
  5. S. Savci2
  1. 1Dokuz Eylül University Institute of Health Sciences, Physical Therapy and Rehabilitation, Izmir, Turkey
  2. 2Dokuz Eylül Üniversite Fizik Tedavi ve Rehabilitasyon Yüksek Okulu, Physical Therapy and Rehabilitation, Izmir, Turkey
  3. 3Dokuz Eylül Üniversitesi Hastanesi, Rheumatology and Immunology, Izmir, Turkey


Background Functional exercise capacity might be affected in ankylosing spondylitis (AS) patients due to factors such as pulmonary function impairment, reduced physical activity, peripheral arthritis, fatigue, muscle weakness and systemic inflammation. In addition to laboratory-based exercise tests, field tests are also used to measure functional exercise capacity. The six-minute walk test (6MWT) which is the most frequently used field test, is valid, reliable, and cost-effective. However, the main disadvantage of the 6MWT is that it allows the patient to set the walking speed. The incremental shuttle walk test (ISWT) is a valid field exercise test of functional capacity. The test requires patients to walk at increasing speeds up and down a 10 m course. The walking speed, which increases every minute, is controlled by audio signals. Performance on the test relates strongly to VO2max, the traditional indicator of cardiorespiratory capacity [1]. Although there are studies evaluating functional exercise capacity in AS patients, no study using ISWT has been found.

Objectives The aim of this study was to investigate the ISWT results and factors associated with this test in patients with AS.

Methods Fifty AS patients aged between 25-58 years (27 males,23 females,) participated in the study. Age, height, weight, body mass index (BMI) were recorded. Disease-specific indices such as Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), Bath AS Metrology Index (BASMI) were used. Sit-up test and push-up test were used to measure muscular endurance. Incremental Shuttle Walk Test (ISWT) was used to assess functional exercise capacity The test was performed in a 10 m course defined by two cones placed 0.5 m from each endpoint. The test was terminated if the patient was unable to maintain the required speed and failed to complete a shuttle in the time allowed for the second time. The total number of shuttles was recorded and distance calculated. Heart rate (HR), blood pressure, perceived dyspnea and leg fatigue (modified Borg Scale) were assessed before and after the test. Age-predicted maximal heart rate (HRmax) was calculated as 220 minus age. Spearman’s correlation coefficients were used to examine the relationship between the ISWT distance and the variables.

Results The mean incremental shuttle walk distance (ISWD) of the patients was 458.40± 98.63 m (min 290 m-max 710 m). Subjects reached 50% of the predicted ISWD according to the reference equation for healthy people [2]. The maximal heart rates were lower than predicted values anticipated for the patients’ age. At the end of the test, subjects reached 57.97±8.62 % of HRmax. ISWD showed significant correlations (p<0.05) with gender (r = 0.488), height (r = 0.474), BASFI (r = -0.313), BASMI (r = -0.397), sit-up test (r = 0.620), push-up test(r = 0.476). However, no relationship was found between ISWD and age, weight, BMI, BASDAI, dyspnea, fatique. Dyspnea and fatigue were not limiting factors for the test. The most common reason for stopping the test was the inability of the patients to maintain the set pace. ISWD has been reported to be associated with age [2], but in our study, unlike the literature, no relationship was found between ISWD and age in AS patients.

Conclusion According to the results of our study, we found that the incremetal shuttle walk test distance in AS patients decreased compared to the reference values reported for healthy individuals. ISWT is associated with factors such as gender, height, functionality, spinal mobility and muscular endurance. ISWT may be appropriate for measuring exercise capacity of AS patients, however, more research is needed.

References [1]Singh S, Morgan M, Hardman A, Rowe C, Bardsley P (1994) Comparison of oxygen uptake during a conventional treadmill test and the shuttle walking test in chronic airflow limitation. European Respiratory Journal 7 (11):2016-2020.

[2]Probst VS, Hernandes NA, Teixeira DC, Felcar JM, Mesquita RB, Gonçalves CG, Hayashi D, Singh S, Pitta F (2012) Reference values for the incremental shuttle walking test. Respiratory medicine 106 (2):243-248

Disclosure of Interests None declared

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