Stronger Feet Are Associated With Lesser Balance Sway

Poor balance increases fall risk, with increasing fall prevalence with age. Maintaining good balance requires coordination, muscular strength, and neurofeedback. A better understanding of the role of toe flexors in maintaining balance across the lifespan is needed. PURPOSE: To determine the correlation between foot strength and standing sway ellipse area with age. METHODS: Twenty-seven participants (10 M/17F; ages 20 - 70 years) completed doming strength tests, and hallux and lesser toes flexion strength tests. Hallux and lesser toes flexion tests measured the strength of the metatarsophalangeal and interphalangeal joints for the first and second through fifth joints, respectively. Doming mimicked the short foot exercise which measures the strength of intrinsic and extrinsic foot muscles. Foot strength measures were normalized to body size (mass*height). Balance tests included side-by-side, semi-tandem, and tandem balance tests barefoot on two feet with eyes open. Participants stood still quietly for 10 seconds on a force plate with foot placement standardized for each balance test. The center of pressure (COP) for each balance test was used to calculate a prediction ellipse that covered 95% of the sway area. Pearson correlation coefficients (r) were calculated to identify relationships between age, foot strength, and balance ellipse area. RESULTS: Normalized doming strength (1.58 ± 0.85 N/kg*m) was moderately and negatively correlated (r = -0.39, p = 0.04) with side-by-side sway area (1.67 ± 0.09 cm2). Normalized lesser toe flexion (163.3 ± 94.5 N/kg*m) was moderately and negatively correlated (r = -0.38, p = 0.05) with tandem sway area (3.5 ± 2.7 cm2). Tandem sway area was also moderately and positively correlated (r = -0.42, p = 0.02) with age (44.5 ± 16.5 years). No other correlations were found between strength measures and balance test sway areas. CONCLUSION: Adults aged 20 - 70 years with stronger doming and lesser toes strength may exhibit better balance in side-by-side balancing and tandem standing than those with weaker toe strength. These results support the efficacy of modalities to increase foot and toe strength to improve balance. However, the sample was highly functional and active and so the influence of physical activity on foot and toe strength measures and balance must be evaluated.