Association between ankle muscle strength and limit of stability in older adults Academic Article uri icon

abstract

  • SIR—Loss of balance and falls in the elderly constitute a major problem associated with human suffering as well as high costs for society [1]. Falls might occur during various daily activities, such as tripping or tangling the feet, reaching movements or bending [2]. Many of these activities are constrained by limits of stability (LOS). LOS can be described as the maximum distance a person can intentionally displace his/her centre of gravity, and lean his/her body in a given direction without losing balance, stepping or grasping. Accordingly, one's LOS capacity is likely to be an important prerequisite for the successful planning and execution of movements such as using a step stool to reach into a high cabinet as well as bending over from standing position to pick up an object from the floor. Ageing is associated with decreased LOS [3–5], muscle strength [6] and foot sensation [7]. Investigators have reported significant correlations between postural stability, quadriceps, ankle dorsiflexion and hand-grip strength [8–11], tibialis anterior latency [8] and functional clinical balance testing [12] among older adults. However, the relationships between lower-limb muscle strength and falls are unclear. Several studies show minimal or no differences in strength between fallers and non-fallers [13, 14] while others show no strength–falls relationships [15]. Cutaneous mechanoreceptors at the soles of the feet contribute to postural stability when standing [16]. Those with reduced feet sensation have a higher risk of falling [17] and greater instability [18]. Reduced foot sensation may contribute to reduced LOS, since older adults might not properly detect when the centre of gravity approaches the LOS. To our knowledge, no one has studied how postural control during LOS relates to ankle strength and foot sensation among older adults. The aims of this study are to investigate how two specific tests of postural control, LOS and postural stability, relate to ankle muscle strength and foot sensation in older adults. Identification of sensorimotor factors associated with both types of balance control can help us to understand better the balance problems facing older adults. Given that LOS likely requires highly active muscular control and that postural stability requires careful sensory monitoring of stance, we hypothesised that ankle muscle strength (and not foot sensation) will be significantly correlated with LOS and that foot sensation (and not ankle muscle strength) will be significantly correlated with postural stability. Data from this study may lead to a better understanding of the mechanisms underlying falls that occur during reaching and bending movements.

publication date

  • January 1, 2008