Limits of stability
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Limits of Stability (LoS) are a concept in balance and stability, defined as the points at which the center of gravity (CoG) approaches the limits of the base of support (BoS) and requires a corrective strategy to bring the center of mass (CoM) back within the BoS.[1] LoS represents the maximum distance an individual can intentionally cover in any direction without losing balance or taking a step.[2] The typical range of stable swaying is approximately 12.5° in the front-back (antero-posterior) direction and 16° in the side-to-side (medio-lateral) direction.[3] This stable swaying area is often referred to as the 'Cone of Stability,' and the limits of the cone of stability vary depending on the specific task being performed.[3]
When the CoG moves beyond the BoS, the individual must take a step or grasp an external support to maintain balance and prevent a fall.[4][5]
These stability limits are perceived rather than physiological; they represent the subject's readiness to adjust their CoG position.[1]: 25
Limits of Stability (LoS) is a reliable variable in assessing stability and voluntary motor control[6] in dynamic states.[7] LoS helps assess balance in the dynamic state by instantaneously tracking the change in COM velocity and COM position.[7]. It measures postural instability while screening for individuals who are at a higher risk of falling[8][unreliable source?]
A restricted LoS significantly influences an individual's ability to react to perturbations in balance control testing. This reduction in LoS may be because of weakness of the ankle and foot muscles, musculoskeletal problems of the lower limb, and/or an internal perception of the subject to resist larger displacements.[9] These impairments can be correlated with medical examination findings and can be used as an outcome measure for rehabilitation of specific underlying body impairments.
From a clinical perspective, individuals who perform complex mobility tasks can function without support and are better able to tolerate environmental challenges.[10]
Possible causes of LoS impairment
- Impaired cognitive processing: This is often associated with aging and can result in attention deficits.[9]
- Neuromuscular impairments: Conditions such as bradykinesia (slowness of movement), ataxia (lack of muscle coordination), and poor motor control[9]
- Musculoskeletal impairments: Weakness, limited range of motion (ROM), and pain in the musculoskeletal system[9]
- Emotional Overlay: Emotions like fear or anxiety[9]
- Aphysiology (exaggeration or poor effort)[9]
