Ankle control differentiation as a mechanism for mobility limitations

Abstract

Independent control of the right and left ankles (differentiation) may be a motor control mechanism linking impaired coordination and mobility limitations. We tested the hypotheses that motor control differentiation of the ankles, as measured using Cross-Sample Entropy, during antiphase coordination at two movement frequencies, is associated with impaired coordination (high ankle coordination variability) and mobility limitations (Short Physical Performance Battery score ≤9). We conducted a cross-sectional study of community-dwelling older adults (N = 133) aged 80.04 (±4.67) years. In linear regression modeling, low ankle Cross-Sample Entropy (low motor control differentiation) was associated with poor (i.e., high) coordination variability at the slower (P = 0.026), but not the faster (P = 0.447), ankle movement frequency. In logistic regression modeling, low Cross-Sample Entropy at the slower (OR = 1.67; 95 % CI: 1.07-2.59) and faster (OR = 2.38; 95 % CI: 1.43-3.94) ankle movement frequencies were associated with increased odds for mobility limitations. Our findings support the hypothesis that ankle differentiation may be a motor control mechanism that links impaired coordination with mobility limitations.

Keywords: Ankle; Coordination; Differentiation; Mobility.

Figure 1.

Exemplar data of angular foot position during 0.5 Hz foot coordination. A. a participant with no mobility limitation and Cross-Sample Entropy = 3.18. B. a participant with mobility limitation and Cross-Sample Entropy = 2.15.