Exercise in Chronic Kidney Disease

The functional decline in chronic kidney disease is multifactorial and largely not renal in the direct sense. Uraemic myopathy produces muscle wasting and weakness independent of disuse. Anaemia from reduced erythropoietin limits oxygen carriage. Chronic inflammation and metabolic acidosis both promote protein catabolism. Renal bone and mineral disorder weakens the skeleton. Fluid shifts, dialysis fatigue, depression, polypharmacy and the sheer time burden of treatment all reduce activity further. On top of this sits the cardiovascular disease that dominates the prognosis, since cardiovascular disease is a major cause of morbidity and mortality across CKD, although prognosis varies substantially with age, stage and comorbidity.

The consequence is a population with markedly reduced exercise capacity, a high prevalence of sarcopenia and frailty, and elevated falls risk. Both sarcopenia and obesity independently raise mortality risk and the likelihood of progression to end-stage disease in established CKD, which makes preserving muscle a clinical objective rather than a cosmetic one. Physical function and physical activity are themselves associated with all-cause mortality and adverse outcomes in non-dialysis CKD, so improving them is not merely a quality of life intervention.

The evidence supports benefit across cardiorespiratory fitness, muscle strength and mass, physical function and walking capacity, blood pressure, quality of life and depressive symptoms.

One question is asked repeatedly and deserves a clear answer: does exercise damage the kidney? It does not. Exercise transiently reduces renal blood flow and can produce a temporary rise in proteinuria that resolves afterwards, and this benign physiological response is sometimes misinterpreted as harm. Regular, appropriately prescribed exercise has not been shown to accelerate decline in kidney function, and it improves physical function, fitness, blood pressure and quality of life. Persistent or unexpected proteinuria still needs clinical interpretation rather than automatic reassurance. The exception to reassurance is rhabdomyolysis from extreme unaccustomed exertion, which is a genuine cause of acute kidney injury but is a different scenario from prescribed regular activity.

The recommendation is the standard adult target of at least 150 minutes of moderate intensity activity a week, or a level compatible with the person's cardiovascular and physical tolerance, with resistance training included because muscle preservation is central. As in any deconditioned population, the realistic starting point is often far below the target and the guidance to do some and then a bit more applies with particular force.

In non-dialysis CKD the prescription is essentially the standard one, combining aerobic and resistance work, with attention to blood pressure, anaemia and bone health. Because cardiovascular disease is so prevalent, symptoms of ischaemia should be taken seriously and assessed rather than attributed to deconditioning.

Haemodialysis introduces specific practical considerations. Intradialytic exercise, performed during the dialysis session itself, is well established and is conventionally delivered within roughly the first two hours, commonly starting about half an hour after dialysis begins. That convention arose from concern that haemodynamic instability increases later in the session, but randomised comparison of exercise in the first versus the second half has not confirmed a higher rate of intradialytic hypotension with later exercise, so timing should follow haemodynamic tolerance and local protocol rather than a rigid rule. A practical target is at least 30 minutes during dialysis, generally three times weekly, supplemented by activity outside dialysis. It uses the otherwise dead time productively and adherence is better than for programmes requiring extra journeys. Exercise outside dialysis can be done on dialysis or non-dialysis days according to fatigue, blood pressure, volume status and individual preference. Blood pressure and volume status vary substantially through the dialysis cycle, so the same programme can feel very different on different days. External compression and blood pressure cuffs should be avoided over the arteriovenous fistula. Loading is a matter for individual assessment rather than blanket prohibition: once the fistula is mature and stable, progressive upper limb activity may be possible with access team advice, monitoring for pain, swelling, bleeding or an altered thrill. In peritoneal dialysis, exercising with the abdomen drained may improve comfort and reduce intra-abdominal pressure for some activities, though it is not mandatory for every session and depends on fill volume, catheter security, hernia risk and the activity planned. Direct catheter trauma should be avoided, with renal team advice for contact or collision activity.

After transplantation, exercise supports cardiovascular risk reduction and helps counter the muscle loss, weight gain and bone loss driven by corticosteroids and calcineurin inhibitors. Activity is built up progressively after the perioperative period. The graft sits superficially in the iliac fossa rather than in the retroperitoneal position of a native kidney, so contact and collision sport warrants transplant team assessment and shared decision-making about graft protection and sport-specific risk rather than universal exclusion.

Most of the caution around exercise in CKD is unwarranted, but a few things are real.

Uncontrolled hypertension, significant electrolyte disturbance, particularly hyperkalaemia, and fluid overload with breathlessness are all reasons to defer a session and address the underlying problem. New or significant symptoms attributable to anaemia warrant assessment and treatment, with exercise intensity adapted meanwhile. Renal bone disease raises fracture risk, so progressive loading is appropriate but high-impact activity and heavy spinal loading need care. Diabetes is common in this population, and where insulin or a sulfonylurea is used the usual hypoglycaemia precautions apply.

Two medication points are worth carrying. Diuretics may contribute to volume depletion and postural symptoms, and renin-angiotensin system drugs may contribute to hypotension or renal vulnerability during dehydration without directly causing volume depletion. Both matter which matters in the heat and during prolonged activity. And non-steroidal anti-inflammatory drugs should generally be avoided in CKD, or discussed with the renal team, particularly around dehydration or prolonged exertion, because the combination of reduced renal prostaglandin-mediated perfusion, dehydration and existing impairment is a recognised route to acute kidney injury. That is a specific and practical piece of advice for anyone reaching for over-the-counter analgesia after training.

• •Physical function predicts mortality in chronic kidney disease, so improving it is a clinical objective rather than a comfort measure.
• •Exercise does not accelerate decline in kidney function; a transient rise in proteinuria afterwards is physiological.
• •Intradialytic exercise is conventionally delivered within the first two hours, though timing should follow haemodynamic tolerance and local protocol.
• •Avoid compression and blood pressure cuffs over the fistula; progress loading only after access team assessment.
• •Draining the abdomen in peritoneal dialysis may improve comfort but is not mandatory for every session.
• •Avoid non-steroidal anti-inflammatory drugs around prolonged exercise in kidney disease.