Perception of Effort During Activity in Patients With Chronic Hepatitis C and Nonalcoholic Fatty Liver Disease.
BACKGROUND
Ratings of perceived exertion (RPE) are used to monitor and prescribe exercise intensity for a variety of patient populations. It is important to understand RPE in different patient populations to ensure appropriate prescriptions and maximize the likelihood of adherence. Chronic liver diseases (CLDs) are a constellation of diseases that are associated frequently with fatigue, metabolic abnormalities, and cardiovascular disease, all targets for prescription of exercise. However, there have been no investigations of the correlates of RPE in those with CLD.


OBJECTIVE
To correlate RPE during a 6-minute walk test (6MWT) with biological/physiological measures in subjects with chronic hepatitis C (CH-C) and non-alcoholic fatty liver disease (NAFLD).


DESIGN
Observational analytical study.


SETTING
Specialty clinic.


PARTICIPANTS
A convenience sample of 51 subjects with NAFLD or CH-C (age: 51.1 ± 8.8 years, 35% female) was enrolled. Subjects receiving antiviral therapies or those with recent myocardial infarction, cardiovascular, or musculoskeletal comorbidities affecting exertion were excluded.


METHODS
Participants underwent fasting morning venipuncture, and resting cardiorespiratory data were collected. Then the participants completed a 6MWT. At the conclusion of the 6MWT, participants reported their RPE, and cardiorespiratory data were reassessed.


MAIN OUTCOME MEASUREMENTS
RPE, 6MWT, resting/postexertion cardiorespiratory data (eg, heart rate, cardiac output), Human Activity Profile (HAP), fasting morning glucose (GLU), total cholesterol (TC), lipids, and interleukin-8 (IL-8) were determined.


RESULTS
For the entire group, RPE was significantly correlated to serum IL-8 and GLU but not to the other factors. When we controlled for age and triglycerides, RPE remained significantly related to GLU (rs = 0.54; P = .04), maximal activity level (HAP) (rs = 0.58; P = .03), and distance walked (rs = 0.61; P = .03) in those with NAFLD. In those with CH-C, only IL-8 remained a strong correlate of RPE (rs = 0.54; P = .01).


CONCLUSIONS
In individuals with CH-C, RPE was related to an inflammatory factor, whereas in individuals with NAFLD, RPE was related to a metabolic and a lifestyle factor.