Muscular and cortical activation during dynamic and static balance in the elderly: A scoping review

Abstract

Falls due to balance impairment are a major cause of injury and disability in the elderly. The study of neurophysiological correlates during static and dynamic balance tasks is an emerging area of research that could lead to novel rehabilitation strategies and reduce fall risk. This review aims to highlight key concepts and identify gaps in the current knowledge of balance control in the elderly that could be addressed by relying on surface electromyographic (EMG) and electroencephalographic (EEG) recordings. The neurophysiological hypotheses underlying balance studies in the elderly as well as the methodologies, findings, and limitations of prior work are herein addressed. The literature shows: 1) a wide heterogeneity in the experimental procedures, protocols, and analyses; 2) a paucity of studies involving the investigation of cortical activity; 3) aging-related alterations of cortical activation during balance tasks characterized by lower cortico-muscular coherence and increased allocation of attentional control to postural tasks in the elderly; and 4) EMG patterns characterized by delayed onset after perturbations, increased levels of activity, and greater levels of muscle co-activation in the elderly compared to younger adults. EMG and EEG recordings are valuable tools to monitor muscular and cortical activity during the performance of balance tasks. However, standardized protocols and analysis techniques should be agreed upon and shared by the scientific community to provide reliable and reproducible results. This will allow researchers to gain a comprehensive knowledge on the neurophysiological changes affecting static and dynamic balance in the elderly and will inform the design of rehabilitative and preventive interventions.

Keywords: Balance; Electroencephalography; Electromyography; Older adults; Postural control.

Fig. 1

PRISMA-flow of the articles selection process.

Fig. 2

Details about the included papers: (a) age of included participants for both elderly (ELD) and younger adult (YOUNG) groups; (b) sample size; (c) number of papers including EEG or EMG (for EMG, relative frequencies of papers investigating lower and upper body are also provided), number of papers investigating cognition and physical activity; (d) frequency bar plots of the muscles analyzed in the papers (relative frequencies are given close to each bar).

Fig. 3

Summary: A) the network of balance control with and without the involvement of cognitive process of sensory signals; B) main observed differences in the cortical signals recorded from the elderly vs younger study participants – power bands are highlighted with the color of the relevant cortical area as in A); C) main observed differences on muscular activity between the elderly and younger study participants.