Lactates sample (100 microliter) will be collected at rest Ankle brachial index is measured at rest transcutaneous oxygen pressure is measured at the chest, calves and buttocks and results will be expressed as the minimal value of the DROP index (Limb changes minus chest changes) Patients walk on treadmill (2MPH 10% slope) until exertional limb pain. Lactates sample (100 microliter) will be collected at minute 3 of recovery from walking Correlation of lactate increase to the sum of DROP values wil be studied