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Exercise is one of the most cost-effective investments in your health, with substantial evidence showing that it can improve chronic conditions in adults. This edition focuses on kidney health and aims to clear up some common misconceptions.

Many people believe that individuals with kidney problems should avoid exercise because excessive physical activity can cause kidney failure. This is a misunderstanding. The primary cause of kidney failure from overexertion is rhabdomyolysis, which we'll discuss in future articles. However, an article published in Nature Reviews Nephrology, titled Exercise and Chronic Kidney Disease: Potential Mechanisms Underlying the Physiological Benefits, explains the mechanisms by which exercise benefits kidney disease. It suggests that exercise is not only a supplementary therapy for kidney diseases but might also aid in the development of new medications.

Chronic Kidney Disease (CKD)

The accumulation of uremic toxins in CKD patients can lead to immune dysfunction, characterized by immunosuppression, reduced antigen responsiveness (including to vaccines), and chronic inflammation. This immune dysfunction is closely related to declining kidney function and increases the risk of cardiovascular disease (CVD) and infections in CKD patients. Notably, CVD and infections are the leading causes of death among kidney disease patients. Therefore, controlling chronic inflammation is crucial for improving the prognosis of CKD patients.

The article indicates that regular exercise helps reduce inflammation markers in non-dialysis CKD patients. Clinical data also support regular exercise for dialysis patients, showing that exercise can lower inflammation without damaging the immune system. It is important to note that if CKD patients exercise for only two months, there may be no significant change in inflammation-related biomarkers. This suggests that at least three months of exercise are required to achieve anti-inflammatory effects. Regarding exercise intensity, moderate to high-intensity interval training is safe for kidney transplant patients, but the specific intensity should be tailored to the patient's age, comorbidities, and exercise history. An individualized exercise prescription ensures safe and effective exercise.

Overall, numerous studies have shown that regular exercise can improve inflammation markers in CKD patients, dialysis patients, and kidney transplant recipients.

Cardiovascular Health

In CKD patients, the risk of developing CVD is much higher than the risk of kidney failure, making CVD the leading cause of death among CKD patients. Maximal oxygen uptake (VO2 max) is an important independent predictor of cardiovascular health and all-cause mortality risk. Data indicate that the progression of CKD leads to cardiovascular damage and a decline in physical fitness.

However, CKD patients who engage in regular exercise have higher VO2 max levels compared to those who are sedentary or exercise irregularly. Multiple global studies have found that regular exercise improves nitric oxide release and bioavailability in CKD patients, enhancing vasodilation, reducing arterial stiffness, and lowering both systolic and diastolic blood pressure, thus benefiting cardiovascular health.

Research indicates that exercise during dialysis can help improve hypertension, left ventricular mass, and blood phosphate levels in dialysis patients. The CYCLE-HD study found that six months of regular exercise was associated with a reduction in left ventricular mass and beneficial left ventricular remodeling. Compared to the irregular exercise group, the regular exercise group had lower levels of myocardial inflammation and fibrosis, which are key factors in arrhythmias and sudden cardiac death. In short, exercise is a non-pharmacological intervention for preventing arrhythmias and sudden cardiac death in CKD patients.

However, the CYCLE-HD study also found that if exercise intensity is too low (below that of cardiac rehabilitation patients), the benefits are not as pronounced. Even so, patients engaging in low-intensity exercise might still benefit through mechanisms such as mRNA release, though more research is needed to confirm these benefits.

In summary, regular exercise of sufficient intensity can improve nitric oxide release and bioavailability, hypertension, left ventricular mass, hyperphosphatemia, arrhythmias, and sudden cardiac death in CKD patients.

Dyslipidemia and Insulin Resistance

Dyslipidemia and insulin resistance are also hallmarks of CKD. Most CKD patients have elevated triglycerides and low-density lipoprotein cholesterol (LDL-C) levels, while their high-density lipoprotein cholesterol (HDL-C) levels are lower, primarily due to impaired lipoprotein metabolism. In early CKD patients, high triglycerides and LDL-C levels are associated with increased mortality risk, while in late-stage CKD patients, lower serum cholesterol is linked to higher mortality. This paradox may be related to systemic inflammation and oxidative stress. Insulin resistance is an early characteristic of CKD and affects nearly all patients with kidney failure.

Early studies suggest that hemodialysis patients can engage in moderate-intensity long-duration exercise (40%-50% of VO2 max) without adverse cardiovascular or metabolic reactions. Long-term regular exercise for six months can improve dyslipidemia and insulin resistance in patients. However, this conclusion is controversial, and more clinical research is needed to verify the effects of exercise on dyslipidemia and insulin resistance in CKD patients.

Sarcopenia

The loss of muscle strength, mass, and function, known as sarcopenia, is common in CKD patients. Sarcopenia can occur in early-stage CKD patients and is related to increased protein degradation rates. Increased protein degradation inhibits skeletal muscle growth and accelerates muscle atrophy. As CKD progresses, factors such as metabolic acidosis, accumulation of uremic toxins, insulin resistance, inflammation, dysregulation of mRNA expression, and reduced physical activity further accelerate muscle atrophy. Some research data show that exercise can slow muscle atrophy and even increase muscle mass in CKD patients, though the mechanisms are not clearly understood.

Healthy kidneys, besides their filtration function, play a role in hormone regulation. When kidney function deteriorates, the regulation and metabolism of vitamin D, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), and Klotho protein are disrupted, leading to issues with bone turnover, volume, growth, or strength and possibly causing abnormal vascular and other soft tissue calcifications. These disturbances are collectively known as chronic kidney disease-mineral and bone disorder (CKD-MBD).

While physical activity can reduce the risk of osteoporosis and fractures, not all exercises are beneficial for CKD-MBD. Some studies indicate that impact load training (like skipping and jumping) and progressive resistance training (muscle training) can stimulate bones, promoting growth and turnover.

In summary, moderate exercise, when maintained long-term, can improve the quality of life for kidney disease patients. However, these benefits are only achievable with appropriate exercise levels. Excessive exercise can not only harm heart function, as discussed in our previous articles, but also exacerbate kidney disease and potentially lead to fatal outcomes. Follow us on medicine.net for more sports medicine knowledge.

Reference:

Bishop NC, Burton JO, Graham-Brown MPM, et al. Exercise and chronic kidney disease: potential mechanisms underlying the physiological benefits. Nat Rev Nephrol. 2023 Jan 17.