Background Osteoarthritis (OA) is the leading cause of mobility limitations in older adults. Ageing is accompanied by changes in body composition characterized by a decline of muscle mass (sarcopenia) and an increase in fat mass. These changes can be extreme to produce “sarcopenic obesity” which is associated with a persistent, sub-clinical proinflammatory state as adipocytes actively secrete proinflammatory cytokines, leading to aggravation of knee OA and mobility impairment.
Objectives This study sought to determine whether modest increases in physical activity through structured exercise would improve muscle strength and decrease muscle fat infiltration and inflammation in older adults with functional limitations due to knee OA.
Methods 198 older patients (131 women and 67 men) with primary knee OA completed a randomized trial consisting of either a physical activity group(PA, n = 99) which included three 40 to 60-min supervised centre-based aerobic, strength, flexibility, and balance training sessions per week or successful ageing health educational control group(SA, n = 99) which consisted of weekly sessions of basic educational information and health topics relevant to older adults with knee OA. Patients were included in the trial if they had clinically symptomatic primary knee OA diagnosed according to the clinical and radiological criteria of the American College of Rheumatology (ACR) with a disease severity graded on the Kellgren-Lawrence (K/L) radiographic system between grade I and III. Study exclusions included severe heart, pulmonary, hepatic and renal disease, cancer, cognitive impairment, Parkinson’s disease and other neurological disease. Isometric knee strength and computed tomography(CT)-derived midthigh skeletal muscle and adipose tissue cross-sectional areas (CSA) as well as inflammatory markers (IL-6, IL-18, IL-I, high sensitivity C-reactive protein (hsCRP), and tumor necrosis factor alpha (TNFα) were measured in duplicate by high-sensitivity enzyme-linked immunosorbent assays (ELISA) and assessed at baseline and at 12 months following randomization. Physical functioning was assessed using the Activities of Daily Living (ADLs) Scale. All assessors were blinded to the intervention group.
Results Total body weight decreased in both groups. Strength adjusted for muscle mass increased significantly (+11.6±8.5%) in the PA compared to the SA group (-20.7 ± 9.9%), p <0.05. Furthermore, there was a significant increase (18.4 ± 6.0%) in muscle fat infiltration in SA, but this gain was nearly completely prevented in the PA (1.2 ± 4.5%) group, p <0.05. A statistically significant decrease in the levels of inflammatory markers was observed in the PA group compared to the SA group. At the end of the study there was a significant improvement in physical function (ADLs scores) in the PA group compared to the SA group.
Conclusions The findings of this study indicate that regular physical activity prevents age-associated loss of muscle strength and increase in muscle fat infiltration in older adults with knee OA. Furthermore, physical activity reduces inflammation and improves physical function. Taken together, these results indicate that physical activity may prevent sarcopenia in older adults with knee OA who are at a high risk for disability.
Disclosure of Interest None Declared