Supervised exercise training (SET) is considered among first-line therapies for patients with symptomatic lower extremity peripheral artery disease (PAD), combined with general cardiovascular risk management, lifestyle adaptation and pharmacological treatment. Although without clear consistency, the guidelines give recommendations in terms of claudication pain severity, SET volume, duration, and frequency. However, no or little guidance is offered as far as training intensity is concerned. Most of the previous studies on SET, in the context of PAD, did not distinguish between symptom intensity and common training intensity measures such as % of maximal heart rate (%HRmax), % of HR reserve (%HRR), % of peak oxygen uptake (%VO2peak), % of VO2 reserve (%VO2R), or the rate of perceived exertion (RPE). In a recent meta-analysis, we demonstrated that both training modality and exercise intensity (based on %peak heart rate, %peak oxygen uptake, or the rate of perceived exertion) should be considered when looking for the best results in patients with symptomatic PAD. These results call for study of the individual roles of each exercise intensity and modality on walking performance and cardiorespiratory fitness in patients with symptomatic PAD. High-intensity interval training (HIIT) is composed of brief bursts of vigorous intensity interspersed with periods of rest or low-intensity exercise. HIIT may be better than moderate-intensity training (MIT) in improving cardiorespiratory fitness and functional capacity in patients with cardiovascular and metabolic diseases, but in patients with symptomatic PAD, the effects of such modalities on walking ability and cardiorespiratory fitness remain to be clearly determined. The primary objective of this study is to compare the effects of 12-week-long exercise training (short-duration high-intensity intervals vs. low-to-moderate intensity) on treadmill performance in patients with symptomatic PAD. It is hypothesized that treadmill performance would be improved to a greater extent after high-intensity exercise training