Intermittent claudication (IC) is a classical symptom reflecting peripheral arterial disease (PAD). IC limits walking capacity and daily functioning 1. Overall treatment strategies are well described in international guidelines 2-4. Limitations in walking distance play an important role in the assessment of disease severity. However, the value of various walking distance assessments is disputed. For instance, patients' estimations of walking distances do not properly reflect objectively measured daily life walking distances 5-7. A disease specific questionnaire such as the Walking Impairment Questionnaire (WIQ) may quantify walking impairments in IC patients better but correlations with walking distances appeared weak 6.
Standardized treadmill tests are widely used as for the objective assessment of walking distances 2-4. However, there is a substantial variability in treadmill protocols 8. In previous studies, fixed inclination was compared with flat off-treadmill walking (in- and outdoors) 5,6,9,10. Interestingly, none of these comparing studies used a graded incremental treadmill test, while such type of testing is recommended in the guidelines for physical therapy because of its high reliability 11,12. Furthermore, previous studies used corridor walking as an imitation of daily life walking 5,6,10. However, IC patients are mostly limited during outside walking with variations in speed, weather condition and surface. Compared to corridor walking, outside walking might be a more reliable reflection of daily life walking.
This study aims to compare the results in walking distances in a group of IC patients using four different tools that are frequently used by physical therapists in the assessment of IC severity. Results of a graded and a non-graded treadmill protocol, patient estimations and outside walking were compared in a single model.