Exercise in Peripheral Arterial Disease

Intermittent claudication is exertional limb pain caused by inadequate arterial supply. The history is characteristic and does most of the diagnostic work: cramping or aching pain in the calf, thigh or buttock, brought on reproducibly by walking a fairly predictable distance, relieved within a few minutes by standing still, and returning at a similar distance again. The site indicates the level of disease, with calf pain suggesting femoropopliteal and buttock or thigh pain suggesting aortoiliac disease. Examination looks for absent or reduced pulses, cool skin, hair loss, delayed capillary refill and ulceration.

The confirmatory test is the ankle brachial pressure index (ABPI), the ratio of the highest ankle systolic pressure to the highest brachial systolic pressure. A ratio of 0.90 or below supports the diagnosis, 0.91 to 0.99 is borderline, and 1.40 or above suggests incompressible arteries and is inconclusive. An important caveat is that heavily calcified, incompressible vessels, classically in longstanding diabetes or chronic kidney disease, can produce a falsely normal or falsely high ratio, so a normal index does not exclude disease in those groups and toe pressures or duplex ultrasound are used instead.

Two differentials matter because both are common and both mislead. Spinal stenosis causes neurogenic claudication, which is typically brought on by standing as well as walking, relieved by sitting or flexing forward rather than simply stopping, and often eased by walking uphill or leaning on a trolley, because flexion opens the canal. Chronic exertional compartment syndrome occurs in a younger active population, builds as tightness or pressure at a predictable exercise dose, may involve paraesthesia or weakness, produces a tense compartment during symptoms, and has no relationship to spinal flexion. Chronic limb-threatening ischaemia, previously called critical limb ischaemia, presents with rest pain, night pain relieved by hanging the leg out of bed, ulceration or gangrene. It is a different problem entirely and needs urgent vascular assessment rather than an exercise programme.

The instinct is that exercising an ischaemic limb must be harmful, and explaining why it is not is usually the difference between a patient completing a programme and abandoning it in the first fortnight.

Several adaptations are likely to contribute, and none of them depends on opening the blocked vessel. Endothelial function improves, skeletal muscle oxidative metabolism improves so the same delivery supports more work, and changes in collateral perfusion may contribute although they do not fully explain the clinical response. Walking efficiency improves through altered gait and better recruitment, reducing the oxygen cost of each step. There is also a genuine element of desensitisation and confidence, since patients who understand the pain is safe walk further before stopping. The practical consequence is that walking distance improves substantially while the resting ankle brachial pressure index typically does not change, which surprises patients and clinicians alike and is worth saying in advance so that an unchanged index is not read as treatment failure.

Current UK guidance is unusually concrete. A supervised exercise programme should be offered to all people with intermittent claudication, and the programme involves two hours of supervised exercise a week for a three-month period, with people encouraged to exercise to the point of maximal pain. In practice sessions are typically structured as a warm-up, a conditioning phase of repeated walking bouts each continued until claudication pain is near maximal, then rest until the pain subsides before the next bout, and a cool-down.

The ordering of treatments is examinable. Supervised exercise comes first. Angioplasty is offered for claudication only when advice on modifying risk factors has been reinforced and a supervised programme has not produced satisfactory improvement. Naftidrofuryl oxalate is considered only where supervised exercise has not helped and the person prefers not to be referred for revascularisation, with progress reviewed at three to six months and the drug discontinued if there is no symptomatic benefit. Evidence from systematic review supports this sequence, with supervised programmes producing meaningfully greater improvements in maximum walking distance than home-based exercise or walking advice, while exercise and revascularisation can both improve walking outcomes, with relative effects varying by anatomy, outcome measure and follow-up.

Provision is the practical problem rather than the evidence. Supervised programmes are unevenly commissioned across the UK, and where none is available a structured home-based programme with behavioural support, monitoring and review is an evidence-based alternative rather than merely walking advice, and in some studies approaches supervised programme outcomes.

The limb symptoms are what bring the patient in, but the wider cardiovascular risk drives long-term morbidity and mortality. Peripheral arterial disease is a marker of generalised atherosclerosis, and these patients carry a substantially increased risk of myocardial infarction and stroke.

Secondary prevention therefore starts concurrently with the exercise programme rather than after it has been tried. That means smoking cessation, which is the single most important intervention and improves both symptoms and survival; statin therapy; antiplatelet treatment; blood pressure management; and glycaemic control where diabetes is present. Foot care deserves specific attention, since reduced perfusion combined with any neuropathy makes minor trauma slow to heal, so well-fitting footwear and inspection matter before a walking programme begins.

Finally, know when exercise is not the answer. Rest pain, tissue loss, ulceration or gangrene indicate chronic limb-threatening ischaemia and require urgent vascular assessment rather than a walking programme. An acutely painful, pale, pulseless, cold limb is acute limb ischaemia and is a surgical emergency.

• •Supervised exercise is first-line for claudication symptoms, with cardiovascular secondary prevention started concurrently.
• •The UK programme is two hours of supervised exercise a week for three months, exercising to the point of maximal pain.
• •Walking distance improves while the resting ankle brachial pressure index typically does not, so an unchanged index is not treatment failure.
• •A ratio of 0.90 or below supports the diagnosis and 1.40 or above is inconclusive, since calcified vessels in diabetes or kidney disease are incompressible.
• •Neurogenic claudication is relieved by sitting or flexing forward rather than simply stopping, and is eased by walking uphill.
• •Rest pain, ulceration or gangrene mean chronic limb-threatening ischaemia and urgent vascular assessment, not exercise.