Age effects on mediolateral balance control

Abstract

Background: Age-related balance impairments, particularly in mediolateral direction (ML) may cause falls. Sufficiently sensitive and reliable ML balance tests are, however, lacking. This study is aimed to determine (1) the effect of age on and (2) the reliability of ML balance performance using Center of Mass (CoM) tracking.

Methods: Balance performance of 19 young (26±3 years) and 19 older (72±5 years) adults on ML-CoM tracking tasks was compared. Subjects tracked predictable and unpredictable target displacements at increasing frequencies with their CoM by shifting their weight sideward. Phase-shift (response delay) and gain (amplitude difference) between the CoM and target in the frequency domain were used to quantify performance. Thirteen older and all young adults were reassessed to determine reliability of balance performance measures. In addition, all older adults performed a series of clinical balance tests and conventional posturography was done in a sub-sample.

Results: Phase-shift and gain dropped below pre-determined thresholds (-90 degrees and 0.5) at lower frequencies in the older adults and were even lower below these frequencies than in young adults. Performance measures showed good to excellent reliability in both groups. All clinical scores were close to the maximum and no age effect was found using posturography. ML balance performance measures exhibited small but systematic between-session differences indicative of learning.

Conclusions: The ability to accurately perform ML-CoM tracking deteriorates with age. ML-CoM tracking tasks form a reliable tool to assess ML balance in young and older adults and are more sensitive to age-related impairment than posturography and clinical tests.

Conflict of interest statement

Competing Interests: With regards to the role of MOTEK Medical BV, this company only provided the software for data collection. This does not alter the authors’ adherence to PLOS ONE policies on sharing data and material.

Figures

Figure 1. Illustration of the set-up and the model for Center of Mass (CoM) calculation utilized in this experiment, showing a silhouette of a subject standing in the middle of a forceplate with marker placement superimposed (in white actual makers and in grey estimated joint centers) and the display of the CoM feedback (red sphere).

The white sphere in the centre represents target which moved in the mediolateral (ML) direction following the patterns depicted in the bottom panel: predictable (top) and unpredictable (bottom). An insertion of foot soles is presented showing foot positioning during the experiments (stance width and angle).

Figure 2. Averaged curves (± sd) for phase shift (top panel), gain (mid panel) and coherence (bottom panel) measures using both, predictable target (left) and unpredictable (right) targets, during first (continuous line) and second (dashed line) sessions and for the younger (in black) and the older adults (in dark grey).

Grey shading indicates the ± sd for all subjects and for all trials. Markers inserted in the plots indicate means for performance descriptors for the first session (circular markers) and second session (diamond markers) for the younger (in black) and the older adults (in dark grey).