Phuong “Lisa” Ha, MSc, & Mathew Debenham, MSc
The University of British Columbia | Okanagan Campus | School of Health and Exercise Science | Sensorimotor Physiology and Integrative Neuromechanics Lab
Take home message
- Older females are weaker and less powerful than younger females but have larger corrective balance responses to postural disruptions.
- Over-corrective balance responses may be linked to greater dorsiflexor activity, greater postural sway and/or less muscle power in older females than young.
- Older females may want to focus on training muscle power to improve balance control.
- Control of standing balance, a critical function for activities of daily living, relies on the vestibular system which also provides awareness of head motion and stabilizes gaze.
- Adult aging is associated with decreased balance control, which may arise from decreased sensory function (e.g., a reduction in the ability of the vestibular system to detect head motion) and age-related muscle weakness.
- Older males have greater corrective balance responses to head motion (i.e., vestibular signals) than young, possibly owing to decreases in the number and quality of vestibular hair cells that detect head movement.
- Following an acute bout of exercise-induced muscle weakness, vestibular information is amplified by the brain to compensate for decrease in muscle force, but it is unknown if a chronic, age-related reduction in muscle weakness leads to a similar trend.
How the study was done
- To evaluate strength and power, 8 young (21-23 years) and 8 older females (63-75 years) performed 3 maximal voluntary isometric contractions (MVCs) as well as fast dynamic knee extensions against resistances ranging from 10-50% MVC.
- Balance and vestibular function were assessed by placing two stimulating electrodes over the mastoid processes to produce vestibular-evoked balance responses (i.e., corrective balance responses) while participants stood quietly on a force plate for two 90-s trials.
- Muscle activity (electromyography; EMG) of the dorsi- and plantar flexors and ground reaction forces were recorded to evaluate balance responses.
- Corrective balance responses were correlated with dorsi- and plantar flexor EMG amplitudes, postural sway variability, and muscle strength and power.
What the researchers found
- The weaker and less powerful older females had greater postural sway variability than the younger females, indicating decrements in balance control.
- Older females also had greater corrective balance responses, as reflected by greater dorsiflexor activity and ground reaction forces.
- Vestibular-evoked balance responses were correlated to dorsiflexor EMG amplitude, postural sway variability, and muscle power, but not plantar flexor EMG amplitude nor strength.
- In addition to greater postural sway variability and vestibular-evoked balance responses, older females had less muscle strength and power compared to young.
- The brain may compensate for age-related decreases in power, by amplifying sensory feedback (e.g., vestibular signals of head motion) to maintain standing balance.
- It is unknown if there is a limit to which the brain can compensate, and older adults may want to focus on power training to maintain muscle power and overall balance.
Ha, P. L., Peters, W. B., McGeehan, M. A., & Dalton, B. H. (2022). Age-related reduction in peak power and increased postural displacement variability are related to enhanced vestibular-evoked balance responses in females. Experimental gerontology, 111670. https://doi.org/10.1016/j.exger.2021.111670