The effect of central processing and muscle torque development speed on balance recovery during standing
Van Schooten KS[1, 2], Sturnieks DL[1, 2], Menant J[1, 2], Brodie MA[1, 3], Lord SR[1, 2] and Delbaere K[1, 2]
1. Falls, Balance and Injury Research Centre, NeuRA, Sydney, Australia
2. School of Public Health and Community Medicine, University of New South Wales, Sydney Australia
3. Graduate School of Biomedical Engineering, University of New South Wales, Sydney Australia
Stepping thresholds, the maximum perturbation one can withstand without taking a step, predict falls in older people (1). This ability may require fast central processing of sensory information followed by rapid execution of adequate motor responses; both processes are impaired with age. This study tests the hypothesis that stepping thresholds are affected by central processing and muscle torque development speed.
Two-hundred forty-two people (80±4yrs;110 ♀) underwent a series of waist-pulls of increasing forces to assess stepping thresholds in anterior, posterior and mediolateral directions. We also assessed simple reaction time and neuropsychological trail making test performance, peak and rate of torque development of knee and hip flexors and extensors and hip abductors in the dominant leg. Data analysis included principal component analysis followed by a multivariate model with participant as random intercept.
We identified four factors represented muscle strength, muscle torque development speed, executive function and processing speed. Weaker (b=-2.9±0.9) and slower (b=-2.1±0.9) muscles, impaired executive functions (b=-2.7±0.9 only for mediolateral direction), and slower processing speed (b=-2.5±0.6) were associated with lower stepping thresholds. Analysis in quartiles revealed that only people in the lowest quartile of muscle strength had significantly lower stepping thresholds (p<=0.014). Stepping thresholds were lowest in the posterior direction (45.5±0.9N), followed by anterior (50.2±0.9N) and mediolateral directions (71.6±1.4N).
Overall, muscle strength showed a threshold effect and executive functions seem particularly important for mediolateral balance recovery. Moreover, central processing and muscle torque development speed affect stepping thresholds and may be important age-related motor impairment targets for preventing falls in older people.
- Sturnieks DL, Menant J, Delbaere K, Vanrenterghem J, Rogers MW, Fitzpatrick RC & Lord SR (2013) PloS one 8(8), e70981