Association between asymmetry in knee extension strength and balance in a community-dwelling elderly population: A cross-sectional analysis

Objective To evaluate the association between balance function and asymmetry of knee extension strength in an elderly Korean population. Methods The strength of the knee extensors in each leg was measured in 306 community-dwelling elderly subjects (age, 76.70±4.85 years) and 25 young healthy subjects (age, 34.23±8.93 years). Based on the difference in strength of both legs, the elderly subjects were divided into symmetric (n=128) and asymmetric (n=178) strength groups using an asymmetry cutoff20%. We determined the postural control ability of the subjects using InBody posturography, Berg Balance Scale (BBS), Timed Up and Go test (TUG) and Short Physical Performance Battery (SPPB). The sway index (SI) of the subjects in four positions was assessed using posturography. Results The group with asymmetric strength presented a significantly higher SI than the group with symmetric strength, in the normal position with eyes open and eyes open on pillows. In the normal position with the eyes closed and in postures with the eyes closed on pillows, the statistical analysis revealed no significant differences between the two groups. The three tests for physical performance (BBS, TUG, and SPPB) show no statistically significant difference between the two groups. Conclusion The asymmetric strength group showed a significantly lower balance than the group with symmetric strength based on several posturographic parameters. Ambulatory elderly individuals with asymmetry in knee extension strength, showed deficits in balance control even in normal clinical tests.