Hip abductor neuromuscular capacity: A limiting factor in mediolateral balance control in older adults?

Abstract

Background: Mediolateral balance impairment is an important cause of falling in older adults. We aimed to investigate whether hip abductor muscular strength and/or position sense are limiting factors in mediolateral balance control. Methods: Sixteen community-dwelling older adults performed three different mediolateral weight-shifting tasks, by tracking (1) a sinusoidally moving visual target, "visual-MELBA"; (2) a sinusoidally translating platform without explicit visual feedback, "mechanical-MELBA"; and (3) an unpredictable platform translation, "sudden-platform-translation." Balance performance was quantified for each task and correlated with hip abductor position sense, isometric strength, and peak hip abduction/adduction moments and moment rates. Findings: Participants with better balance performance showed higher and faster hip abduction/adduction moment production during the tasks. Isometric hip abductor strength was significantly correlated with accuracy of tracking the visual target, while hip abductor position sense was associated with the bandwidth over which the mechanical target could be tracked and with a smaller delay between CoM movement and the sudden-platform movement. Interpretation: Hip abductor muscles play an important role in mediolateral balance control. Accurate balance performance appears limited by lower hip abductor strength when explicit visual information on balance reduces the need for hip abductor proprioception, while proprioceptive acuity may limit balance performance when no explicit enhanced feedback is presented and required weight shifts have to be inferred from "normal" sensory information.

Assessing age-related balance deterioration: Visual or mechanical tasks?

“…A previous study by our group also found a lower control bandwidth during MELBA in older than in young adults and with similar overall performance values (Cofré Lizama et al, 2014). This balance deterioration can partly be attributed to a decreased hip abduction-adduction strength and torque production in older adults population as these muscles are some of the main actuators in the displacement of the CoM in the frontal plane (Arvin et al, 2015;Arvin et al, 2016;Chang et al, 2005;Johnson et al, 2004). However, deterioration of other systems with ageing such as vision and attention, which are highly challenged during visual MELBA, may also have a negative effect on balance control (Maki et al, 2001;Maki and McIlroy, 2007).…”

“…This suggests that mechanical MELBA may impose a greater challenge for the balance control system requiring a change in motor strategy in both age groups to cope with the task (similar change in PS angle ). These strategies may involve an increasing use of hip musculature and trunk-legs decoupling, as seen in previous studies using surface perturbations (Arvin et al, 2016;Jilk et al, 2014). We used the average angle phase-shift (PS angle ) within PS mean as an overall measure of the strategies utilized during both tasks and both targets.…”

“…Perfect performance implies a zero degrees PS (no delay) and a gain equal to one (same amplitude) over all frequencies comprised in the target signal. As in our previous studies (Arvin et al, 2016;Cofré Lizama et al, 2014;Cofré Lizama et al, 2015b), the frequencies at which the PS dropped below 90°and gain dropped below 0.5 were determined as the cut-off frequency for phase shift (f PS ) and gain (f G ). These performance descriptors indicate the bandwidth of adequate balance control within the task.…”

“…The aim of this study was to determine whether performance in the original MELBA (visual-MELBA) or a modified MELBA using tracking of surface translations (mechanical MELBA) with slightly modified waverforms is more sensitive to balance deterioration in communitydwelling older adults. Although Arvin et al (2016) used the mechanical tracking in older adults to determine the effects of strength and proprioception, no comparison to young adults was performed (Arvin et al, 2016). Further, other studies by Cofré Lizama et al (2013, 2014 and 2015a, b) have only used visual tracking tasks (Cofré Lizama et al, 2013, 2015aCofré Lizama et al, 2014;Cofré Lizama et al, 2015b).…”

“…Furthermore, to our knowledge, this is the first study comparing young and older adults balance performance during mechanical and visual tracking tasks. Based on previous literature that has shown an increased visual reliance accompanied or compensatory to proprioceptive deterioration and an increased challenge of the latter system during surface translations (Arvin et al, 2016), we hypothesized that the mechanical MELBA may be more sensitive to ageing than the originally proposed visual tracking task.…”