Introduction: Supervised exercise training is among the first-line therapies for patients with peripheral artery disease (PAD). Current recommendations for exercise include guidance focusing on claudication pain, programme and session duration, and frequency. However, no guidance is offered regarding exercise training intensity. This study aims to compare the effects of 12-week-long supervised walking exercise training (high-intensity interval training (HIIT) vs moderate-intensity exercise (MOD)) in patients with chronic symptomatic PAD. Methods and analysis: This study is a monocentric, interventional, non-blinded randomised controlled trial. 60 patients (30 in each group) will be randomly allocated (by using the random permuted blocks) to 12 weeks (three times a week) of HIIT or MOD. For HIIT, exercise sessions will consist of alternating brief high-intensity (≥85% of the peak heart rate (HRpeak)) periods (≤60 s) of work with periods of passive rest. Patients will be asked to complete 1 and then 2 sets of 5–7 (progressing to 10–15×60 s) walking intervals. For the MOD group, exercise training sessions will consist of an alternation of periods of work performed at moderate intensity (≤76% HRpeak) and periods of passive rest. Interventions will be matched by training load. The primary outcome will be the maximal walking distance. Secondary outcomes will include functional performance, functional capacity, heath-related quality of life, self-perceived walking abilities, physical activity and haemodynamic parameters.