Introduction: With their high incidence and associated costs, falls form a considerable problem in modern society. Every year, more than one third of people over 65 years experience fall that much of it occurs while walking. So to prevent this phenomenon, it seems that assessment of gait stability is a logical step. Indicators such as variability that are used to predict fall risk, can not quantify how a motor system respond to disturbances and do not have the ability to provide mechanical vision on how to maintain stability while walking. This study using a non-linear method, investigated walking stability of active and inactive healthy elderly and young males and how to change it by changing the speed of walking.
Methodology: 24 healthy older adults (64.92±6.82 years) and 25 young adults (26.69±3.01 years) walked 10 sets of 95 s (two sets per speed) on a treadmill at speeds of 80–120% of their preferred speed. Kinematic data was recorded using a 6-camera system (100 Hz). Maximum FM (orbital stability) and maximum Lyapunov exponents (local stability) were quantified. Also, passive joints range of motion and isometric strength of the muscles of lower extremities were measured. Two-factor repeated measure ANOVA and ANCOVA used for statistical analysis (p≤0.05).
Results: Local and orbital stability differences in hip, knee and ankle joints were significant between 4 groups. Walking speed had significant effect on hip and ankle local stability, but all groups showed no significant differences in orbital stability between different speeds. While all these differences also remained significant by engaging the power and range of motion combined scores.
Discussion: Due to results, it seems that older adults walk with lower local and orbital stability than young adults. However, walking with lower speed improves the local and orbital stability, but results in greater variability. Therefore, age-related differences in local and orbital stability partly justified by lower strength and flexibility.