Age-related changes in leg proprioception: implications for postural control

Abstract

In addition to being a prerequisite for many activities of daily living, the ability to maintain steady upright standing is a relevant model to study sensorimotor integrative function. Upright standing requires managing multimodal sensory inputs to produce finely tuned motor output that can be adjusted to accommodate changes in standing conditions and environment. The sensory information used for postural control mainly arises from the vestibular system of the inner ear, vision, and proprioception. Proprioception (sense of body position and movement) encompasses signals from mechanoreceptors (proprioceptors) located in muscles, tendons, and joint capsules. There is general agreement that proprioception signals from leg muscles provide the primary source of information for postural control. This is because of their exquisite sensitivity to detect body sway during unperturbed upright standing that mainly results from variations in leg muscle length induced by rotations around the ankle joint. However, aging is associated with alterations of muscle spindles and their neural pathways, which induce a decrease in the sensitivity, acuity, and integration of the proprioceptive signal. These alterations promote changes in postural control that reduce its efficiency and thereby may have deleterious consequences for the functional independence of an individual. This narrative review provides an overview of how aging alters the proprioceptive signal from the legs and presents compelling evidence that these changes modify the neural control of upright standing.

Adaptation of balancing behaviour during continuous perturbations of stance. Supra-postural visual tasks and platform translation frequency modulate adaptation rate

“…Exercises based on head movement have been beneficial in patients with vestibulopathy [ 129 ]. Prolonged exposure to optical flow during mechanical whole-body perturbations creates the conditions for modulating the integration of the proprioceptive, vestibular and visual inputs [ 58 , 59 , 130 – 132 ]. The present protocol might be valuable to further investigate the sensorimotor processes subserving calibration of dynamic balancing behaviour [ 133 ].…”

“…whole-body perturbations creates the conditions for modulating the integration of the proprioceptive, vestibular and visual inputs [58,59,[130][131][132]. The present protocol might be valuable to further investigate the sensorimotor processes subserving calibration of dynamic balancing behaviour [133].…”

Corticospinal responses during passive shortening and lengthening of tibialis anterior and soleus in older compared to younger adults

“…To gain insight into the responsiveness of muscle spindle afferents in older age, future studies could consider using microneurography to directly record the activity of different afferent fibres. Given muscle spindle receptors are considered the primary source of proprioceptive information (Henry & Baudry, ), and their involvement in triggering rapid postural responses to unexpected perturbations (Stapley, Ting, Hulliger, & Macpherson, ), the impairment in processing and integration of information from muscle spindles could be considered a contributing factor in altered postural control in older age.…”

“…Healthy ageing is characterised by alterations in both the motor pathway of the central nervous system (CNS) and proprioception, which can have significant implications for postural control (Henry & Baudry, 2019). Some evidence suggests that ageing affects sensory to a greater extent than motor axons, as evidenced by prolonged latency of the H-reflex (Scaglioni, Narici, Maffiuletti, Pensini, & Martin, 2003).…”

Influence of age on the frequency characteristics of the soleus muscle response to Achilles tendon vibration during standing

“…Ageing is known to influence the structure and function of many aspects of the sensorimotor system ( Fig. 1) and these changes lead to impaired mobility and increased risk of falls (Ferlinc et al 2019;Henry and Baudry, 2019). Many components of the stretch reflex pathway are affected by ageing, including muscle spindle mechanoreceptors and their afferent axons (Swallow, 1966;Swash and Fox, 1972;Liu et al 2005;Kim et al 2007;Vaughan et al 2017), as well as α-motoneuron axons and cell bodies, neuromuscular junctions, and muscle fibres (Lexell and Downham, 1991;Zhang et al 1996;Hepple and Rice, 2016).…”