Eight weeks of aerobic exercise training increased peak oxygen uptake by muscle and muscle mass, and reduced fatigue, in patients with cirrhosis, researchers report in the November issue of Clinical Gastroenterology and Hepatology.
Cirrhosis is characterized not only by hepatic fibrosis and progressive liver dysfunction, but also reduced exercise tolerance, based on decreased peak exercise uptake of oxygen (peak VO2). Even patients with early-stage cirrhosis have 40% lower peak VO2 values than healthy people.
Laura Zenith et al. performed a pilot study to evaluate the effects of supervised exercise on peak VO2, muscle mass, and quality of life in 19 patients with Child–Pugh class A or B cirrhosis (79% male; average age, 58 years).
The patients were randomly assigned to groups that received exercise training (n = 9) or usual care (controls, n = 10). The exercise group rode a cycle ergometer 3 days/week for 8 weeks at 60%–80% of their baseline peak VO2. At each session, the patients warmed up for 5 minutes with low-level cycling and then cycled for 30 minutes, increasing by 2.5 minutes each week. Each session was followed by a 5-minute cool down.
After the 8-week period, the patients who received the exercise training had peak VO2 values 5.3 mL/kg/min greater than those of controls. They also had significantly greater thigh circumference, thigh muscle thickness, and perceived health status, as well as less fatigue than controls. No adverse events occurred during cardiopulmonary exercise testing or training.
Zenith et al. say that these findings are important because in healthy populations, an increase of 3.5 mL/kg/min has been associated with a 12%–18% increase in survival. Aerobic exercise improves blood flow to skeletal muscles and oxygen extraction by active muscles to increase peak VO2 values.
The increase in muscle thickness observed in the exercise group is significant because muscle wasting is an independent predictor of mortality in patients awaiting liver transplants.
Zenith et al state that the study was limited by the small population and the fact that the patients all had early-stage disease. However, they say that the lack of adverse outcomes supports the performance of larger trials, possibly in patients with more advanced disease.
Only aerobic exercise was evaluated in this study, so it will be interesting to learn whether resistance training, alone or in combination with aerobic training, is also safe or even more effective for patients with cirrhosis.
Future studies are needed to confirm these findings and determine the mechanisms that impair the aerobic capacity of patients with cirrhosis.
The authors also hope to learn whether exercise affects clinical outcomes, such as retained functional status and reduced mortality.