Inclusion Criteria:  LEAD group: Patients with diagnosis of lower extremity arterial disease (Fontaine IIa). Control group: Healthy volunteers with no leg symptoms and an ankle-brachial index (ABI) of 1.0-1.4.  Exclusion Criteria:  Fontaine stages I or IIb-IV Exacerbation of limb ischaemia within the preceding 2 weeks; strong rest pain of any cause; age <18 or >80 years; fasting < 6 hours; time since last use of tobacco products < 6 hours; body mass index ≥ 35 kg/m2 poor sonographic visibility of femoral artery; angina; cardiac arrhythmia at the time of presentation; presence of cardiac pacemaker; myocardial infarction within the preceding 3 months; stroke within the preceding 6 months; ongoing anticoagulant therapy; ongoing dual antiplatelet therapy; any revascularization within the preceding 3 month; marked heart failure (NYHA III-IV); blood pressure ≥ 180/110 mmHg; blood pressure <100/70 mmHg; clinically significant heart valve disease; acute infectious disease; active malignancy or chemotherapy or disease-free < 5 years; type I diabetes or insulin therapy; other clinically significant and untreated endocrine disorders; moderate to severe bronchial asthma (GINA 2016); severe chronic obstructive pulmonary disease (mMRC grade 3-4); acute (KDIGO 2012) or chronic renal disease (eGFR-EPI <30mL/min/1.73 m2); acute or chronic liver disease; anemia (<110 g/L); neuroinflammatory or neurodegenerative disease; active rheumatism; other diseases and factors that markedly hinder the subject's ability to walk during the treadmill exercise. For control group exclusively: history of lower extremity arterial disease / ABI <1.0 or >1.4.