Sensory Variables Affecting Balance
This article was researched and documented by Sonia R, OTR/L.
Falls occur when there is a loss of balance with an inability to control one’s posture.
Sensory input, the external information received from our surroundings, influences our balance. Three types of sensory input received include:
- Visual input (e.g. vision)
- Proprioceptive input (e.g. joint position, related to standing surface)
- Vestibular input (e.g. head positioning)
These, together with postural reflexes, help with postural control.
As we age, there are declines in the sensory and motor function that affect balance. When balance is affected, this can lead to falls, or a fear of falls, which may lead to decreased participation in the home and community, isolation, inactivity, and possibly decreased independence.
Research
One study looked at how these three sensory variables can affect balance, specifically, postural sway. Postural sway is the movement of the center of mass while standing, and postural control is the ability to maintain the center of mass within the base of support with minimal postural sway [2]. Pociask, et. al. (2016) explored the involvement of head position, along with vision and standing surface, and their contributions to postural sway in older adults. They assessed this in a group of community-dwelling older adults 60 yrs or older, free from physical/medical difficulties that would influence balance. Participants were required to stand and try to maintain their balance under eight different condition combinations of: eyes open or closed, on a firm or foam surface, and head neutral or extended.
Significant results showed postural sway increased: 1) On both firm and foam surfaces, with eyes closed, 2) On both firm and foam surfaces, with head extended, 3) With eyes open and eyes closed, with head extended; and the most postural sway occurred: 4) On a foam surface with eyes closed and head extended. These findings aligned with their initial hypothesis, that head extension increased sway for all visual-surface conditions.
Conclusion/Implications
The results of this study indicate that head position is relevant to address when assessing functional tasks involving head extension, as this may put older adults at risk for loss of balance, resulting in falls. Furthermore, this risk increases when on a soft surface with vision occluded.
This is applicable to daily life:
- Looking upward with eyes closed to wash soap from face when showering
- Tilting head when retrieving item from cabinets above eye level
- Walking on grass, carpet/rugs, snow, in dim or dark lighting
- While on the subway train looking up to reach the pole
- Pulling clothes on over your head
As therapists, understanding the relationship between standing surface, vision, and head position in regards to balance, will allow for better intervention in client education, environmental adjustments, and fall prevention when performing daily life activities, therefore increasing safety and functional independence in older adults.
