Exercise physiology in cirrhosis and the potential benefits of exercise interventions: A review

Abstract

Reduction in muscle mass is a highly prevalent phenomenon in cirrhosis and is now well-documented to be associated with significant morbidity and mortality. Research into muscle loss in cirrhosis remains limited by an ongoing poor understanding of its relationship with muscle function, physical activity, and aerobic capacity. Alterations in exercise physiology have been documented in studies of individuals with cirrhosis that provide important information on physical function that is not captured by simple quantification of muscle mass. Despite expert consensus recommending regular exercise in end-stage liver disease to maintain muscle mass and function, there is little evidence guiding clinicians as to which form of exercise or delivery mechanism is most effective. It also remains unproven whether any specific intervention can alter clinically relevant outcomes. This review article summarizes the available literature regarding the changes in exercise physiology observed in cirrhosis, the associated impact on physical capacity, and the results of existing trials that examine the potential benefits of exercise delivery in patients with cirrhosis, particularly pertaining to their impact on exercise physiology. MethodsArticles were retrieved via a search of Pubmed and MEDLINE via Ovid in April 2020. Databases were searched from inception to April 2020 using the MeSH terms "Liver Disease," "Liver Transplantation," "Exercise," "Exercise Therapy," "Physical Activity," "Activities of Daily Living," "Muscular Atrophy," "Frailty," "Muscle Strength," or "Muscle Mass." Prominent authors in the field, other relevant journals, and primary source reference lists were searched manually. All articles examining exercise interventions that included at least three patients with cirrhosis were included. Publications that included only patients with non-cirrhotic liver disease or exclusively post-liver transplant subjects were excluded. Controlled and observational studies were included; however, case reports were not. ResultsAlterations in exercise physiology in cirrhosis. Severe malnutrition is common in cirrhosis; reduced total energy intake combined with derangement of complex metabolic pathways results in substantial loss of skeletal muscle mass and function. 3 These metabolic derangements cause patients to derive a lower proportion of energy from carbohydrate, evidenced by low respiratory quotients in patients with cirrhosis as measured by indirect calorimetry. 14 Reduced hepatic glycogen stores drive an

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