Effects of exercise and diet on knee strength in older overweight and obese adults with knee osteoarthritis.

Abstract

0638 INTRODUCTION: Previous studies have shown a strong association between obesity and knee osteoarthritis (OA). Felson and colleagues (2000) identified biomechanical factors associated with OA in weight-bearing joints, including obesity, muscular weakness, and joint laxity. Studies indicate that both obese adults (Kitagawa, 1978) and adults with knee OA (Messier et. al., 1992) are weaker than age-matched healthy controls. Short term resistance training has been shown to improve strength in older adults (Morganti, 1995), and long term resistance training in older adults with knee OA has shown significant, but modest improvements in function and strength compared to walking or a control group (Ettinger et.al.,1997). PURPOSE: Therefore, the purpose of our study was to determine the effects of exercise and dietary weight loss on muscular strength in older overweight (BMI = 28–30) and obese (BMI > 30) adults with knee OA. METHODS: A cohort of 316 older overweight and obese adults (BMI > 28) with radiographic evidence of knee OA were randomized to one of four groups: diet (D), exercise (E), diet and exercise (D&E), or healthy lifestyle control (HL) (The Arthritis Diet and Activity Promotion Trial (ADAPT)). Exercise sessions consisted of two 15-minute bouts of walking separated by 20 minutes of moderate intensity resistance training. The E and D&E groups underwent 6 months of facility-based exercise. Subsequently, participants had the option to continue in the facility-based program for an additional 12 months, transition to a home based exercise program, or combine the facility and home based programs. Dietary intervention focused on reducing fat and total calories. Weight loss goal was 5% of body weight. Bi-lateral knee strength data (concentric/eccentric flexion, concentric/eccentric extension) were collected on a randomized subset of this cohort (n = 156 at baseline) using a Kin-Com isokinetic dynamometer set at a speed of 30 deg/s. Data were collected at baseline (BAS), 6 months (FU6), and upon completion of the intervention (FU18). DATA ANALYSIS: Data were averaged over a range of 80–40 deg knee flexion (0 = extension). Knee flexion/extension strength were analyzed using the average values over this range of motion. The effects of diet and/or exercise programs on muscular strength measured at 6 and 18 months post-randomization were determined by twoway repeated measures analysis of covariance. Estimates of intervention effects were obtained at each follow-up observation. When group-by-time interactions were nonsignificant, average intervention effects over the follow-up period were estimated and tested for significance.