Age-Related Changes in the Neural Control of Standing Balance

Abstract

Controlling body sway while standing is an active process involving lower as well as higher neural centers. This chapter examines how the central nervous system controls undisturbed standing balance and summarizes the current knowledge concerning the effects of task difficulty and old age on postural control of standing. There is an age-related reorganization of neural control of standing, with decreased efficacy of Ia afferents to activate spinal motor neurons, increased cortical activation and corticospinal excitability, and reduced intracortical inhibition. Age does not affect the motor control strategy of reducing intracortical inhibition with increasing postural challenge. However, the threshold for down-modulation decreases with aging. It thus seems that motor cortical involvement in the control of standing balance becomes more prominent with age and postural task difficulty. Future studies will determine if it is beneficial and necessary through interventions to reduce the cortical involvement in the control of standing balance in healthy old adults especially if this involvement should increase in old adults with a history of falls.

Age-related reversal of spinal excitability during anticipatory postural control

“…These data add to the emerging view of age-related impairments in the inhibitory neural control of voluntary movement (Baudry et al 2015; Levin et al 2014; Papegaaij and Hortobágyi 2017). …”

“…Under appropriate experimental controls, we found that the stereotypical H reflex depression associated with an APA in younger adults (age ~ 21) was reduced in middle-aged adults (age ~ 47) and reversed to facilitation in healthy older adults (age ~ 70). These data add to the emerging view of age-related impairments in the inhibitory neural control of voluntary movement (Baudry et al 2015 ; Levin et al 2014 ; Papegaaij and Hortobágyi 2017 ).…”

“…For example, it is unclear if older age affects reflex excitability present during a self-perturbation-induced APA. As aging decreases cortical inhibitory processes in general (Papegaaij et al 2014) and because the age-related reduction in the excitability of inhibitory circuits in the primary motor cortex is accompanied by a decrease in the contribution of Ia afferent input to the activity of muscles controlling posture (Baudry et al 2015; Papegaaij and Hortobágyi 2017), we hypothesized that age affects reflex excitability associated with APA by reducing the magnitude of depression. In other words, we expected an age-related disinhibition of H reflexes during APAs.…”

Acute Improvement of Postural Steadiness Through Neuromuscular and Proprioceptive Training in Sedentary Older Females

“…Besides, one exercise session may increase the conductivity of the nerves (41)(42)(43), which is part of the sensorimotor mechanism. The sensitivity of lower extremity proprioception declines with normal aging (43,44), and this decline has been associated with an increase in postural swaying (2,3,38,45,46) and with a history of falling (38). According to the study, the decrease in COP velocity after a single NPT session occurred in the ML plane under the CE condition.…”

“…The percentage of people over the age of 60 years in the global population, according to the forecast of the World Health Organization will increase from 10.0% in 2000 to 21.8% in 2050, and then to 32.2% in 2100 (1). The natural aging process is associated with poor balance ability and reduction in the joint position sensation (2,3). Women are generally weaker than men in all age groups (4,5).…”