KNEE FLEXION AND EXTENSION STRENGTH IN OLDER ADULTS TRANSITIONING TO FRAILTY

Abstract

828 Several investigators have examined knee flexion and extension strength in older adults to better understand the etiology of falls and the role of leg strength in the prevention of falls. However, most of these studies have examined only healthy/robust subjects. In this study, we examined knee flexion and extension strength in 20 subjects (19 females, 1 male; age=79.1±5.8 yrs.) who were transitioning to frailty, as determined by Speechley-Tinetti (1991). Using a KinCom isokinetic dynamometer (Model AP 180), knee extension and flexion strength were measured for each leg separately at two speeds (60°/s and 90°/s), for a total of 8 test conditions. Three warm-up repetitions were performed, followed by 3 test repetitions for each movement condition. Movement conditions were randomized within each leg. Peak torque (PT), angle at peak torque (APT), and time to peak torque (TPT) were recorded. A repeated-measures ANOVA was utilized to determine significant differences. Significant main effects were found for PT (p<.0001; Mflex=25±9 Nm, Mext=58±17 Nm) and TPT (p<.0001; Mflex=0.32±0.14 s, Mext=0.47±0.13 s) for Movement, and for TPT (p<.0001; M90°/s=0.35±0.12 s, M60°/s=0.45±0.17 s) for Speed. No significant interactions were found. During knee extension, subjects produced greater torques and reached peak torque later in the ROM than during flexion. Subjects took longer to reach PT at 60°/s than at 90°/s. The flexion:extension ratio for PT was 0.43, much lower than the ratios that have been reported for young adults (Aagaard et al., 1998) and for robust older adults, aged 58-70 yr. (Lan et al., 1998). Repetitive measures of leg strength in this population may enhance our understanding of the changes in strength associated with aging, as well as the etiology of falls and the effectiveness of strength interventions for preventing falls. Supported by NIH Grant AG14767.