The effects of age and central field loss on maintaining balance control when stepping up to a new level under time-pressure

Tjerk Zult; Matthew A Timmis; Shahina Pardhan

doi:10.7717/peerj.14743

The effects of age and central field loss on maintaining balance control when stepping up to a new level under time-pressure

PeerJ. 2023 Feb 20:11:e14743. doi: 10.7717/peerj.14743. eCollection 2023.

Authors

Tjerk Zult¹, Matthew A Timmis^{1

2}, Shahina Pardhan¹

Affiliations

¹ Vision and Eye Research Institute, School of Medicine, Faculty of Health, Education, Medicine, and Social Care, Anglia Ruskin University, Cambridge, Cambridgeshire, United Kingdom.
² Cambridge Centre for Sport and Exercise Science, Anglia Ruskin University, Cambridge, Cambridgeshire, United Kingdom.

Abstract

Objective: To investigate the effects of age and central field loss on the landing mechanics and balance control when stepping up to a new level under time-pressure.

Methods: Eight older individuals with age-related macular degeneration (AMD), eight visually normal older and eight visually normal younger individuals negotiated a floor-based obstacle followed by a 'step-up to a new level' task. The task was performed under (1) no-pressure; (2) time-pressure: an intermittent tone was played that increased in frequency and participants had to complete the task before the tone ceased. Landing mechanics and balance control for the step-up task was assessed with a floor-mounted force plate on the step.

Results: Increased ground reaction forces and loading rates were observed under time-pressure for young and older visual normals but not for AMD participants. Across conditions, loading rates and ground reaction forces were higher in young normals compared to older normals and AMD participants. Young visual normals also demonstrated 35-39% shorter double support times prior to and during the step-up compared to older normals and AMD participants. All groups shortened their double support times (31-40%) and single support times (7-9%) in the time-pressure compared to no-pressure condition. Regarding balance control, the centre-of-pressure displacement and velocity in the anterior-poster direction were increased under time-pressure for young and older visual normals but not for AMD participants. The centre-of-pressure displacement and velocity in the medial-lateral direction were decreased for the AMD participants under time-pressure but not for young and older visual normals.

Conclusions: Despite walking faster, AMD participants did not adapt their landing mechanics under time-pressure (i.e., they remained more cautious), whilst older and young adults with normal vision demonstrated more forceful landing mechanics with the young being most forceful. A more controlled landing might be a safety strategy to maintain balance control during the step-up, especially in time-pressure conditions when balance control in the anterior-posterior direction is more challenged.

Keywords: Age-related macular degeneration; Human locomotion; Mobility; Postural control; Time pressure; Visual impairment.

MeSH terms

Humans
Postural Balance*
Walking*
Young Adult

Grants and funding

This work was supported by an Anglia Ruskin Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.