ANKLE PLANTARFLEXOR POWER IS ASSOCIATED WITH AMBULATORY BALANCE AND POSTURAL PERTURBATIONS IN OLDER ADULTS

J. Garland¹, D. Arsenault², T. Ivanova²

¹Western University, Physical Therapy, London, Canada, ²Western University, Health Sciences, London, Canada

Background: Falls are a primary cause of injury in individuals over the age of 65 and are a main source of physiotherapy intervention in older adults. A decline in lower limb muscle power has been associated with functional mobility impairments in older adults. Ambulatory balance is of paramount importance for community dwelling older adults.

Purpose: We sought to determine the association between muscle power output around the ankle joint to ambulatory balance performance and response to external perturbations in older adults. We hypothesized that older adults with higher ankle muscle power would have higher levels of ambulatory balance and be able to withstand higher intensity perturbations without taking a step.

Methods: Ambulatory balance was assessed using the Community Balance and Mobility Scale (CB&M). Ankle muscle power was assessed using a Biodex System 3 isokinetic dynamometer. Surface translation perturbations were performed with a split belt treadmill. The intensity of the posteriorly-directed treadmill perturbations (unilateral or bilateral) was set by increasing belt velocity until a step was required. The intensity was then decreased to just below that which required a step. Participants were unaware of the exact timing of the perturbations. To determine the relationship between muscle power, and ambulatory balance and perturbation intensity, spearman correlations were used.

Results: Twenty healthy older adults (eleven males and nine females; mean age 76.6 ± 5.5 years) participated in the study. The mean CB&M score was 63.1 ± 12.9 (/96), the mean average isotonic power was 23.9 ± 10.5 W and 4.9 ± 2.2 W for ankle plantarflexor and dorsiflexor muscles, respectively. There was a significant positive correlation between plantarflexor power and CB&M score (ρ₌0.464; p=0.04), but not between dorsiflexor power and CB&M score (ρ=0.314; p>0.05). A significant correlation was observed also between plantarflexor power and unilateral perturbation intensity (ρ =0.486; p=0.03), but not between plantarflexor power and bilateral perturbation intensity (ρ =0.293; p>0.05).

Conclusions: An increase in ankle plantarflexor power was associated with higher levels of ambulatory balance and an ability to withstand higher intensities of unilateral support surface perturbations in older adults.

Implications: Maintaining ankle plantarflexion power during the aging process may be critical in the maintenance of not only functional ambulatory balance performance, but also the postural response to external perturbations. Physiotherapists should consider assessing ankle muscle power in older adults under their care.

Funding acknowledgements: This work was unfunded.

Keywords:
Standing balance
Muscle power
Older adults

Topics:
Community based rehabilitation
Older people
Musculoskeletal: lower limb

Did this work require ethics approval? Yes

Institution: Western University

Committee: Western Health Sciences Research Ethics Board

Ethics number: 110471