Muscle co-contraction in elderly people change due to postural stability during single-leg standing

Abstract

BackgroundMuscle co-contraction is the simultaneous contraction of agonist and antagonist muscles crossing a joint, and it increases with age. This study primarily aimed to clarify the difference in the effect of a light fingertip contact to stationary surface on postural sway and muscle co-contraction during single-leg standing (SLS) between young and elderly groups; the secondary aim was to reveal the quantitative difference in the muscle co-contraction of the ankle joint among the three different support structure conditions in the elderly group.MethodsThis study included eight young adults (age 23.4 ± 2.6 years) and nine community dwelling older adults (age 74.7 ± 3.4 years). The task was SLS under the following conditions: (1) no supporting structure, FR; (2) light index fingertip contact to a stationary supporting structure (to touch in force < 1 N), LT; and (3) dependence on a supporting structure for stabilization as desired, DO. Center of pressure (COP) variables [root-mean-square distance (RDIST), total excursion (TOTEX), mean velocity (MVELO), and standard deviation area (AREA-SD)] and the co-contraction index (CI) between the tibialis anterior and soleus were measured using surface electromyography.ResultsWith regard to the effect of the light fingertip contact to stationary surface, in the young group, TOTEX, MVELO, AREA-SD, and CI during SLS were smaller under the LT condition than under the FR condition. However, in the elderly group, only AREA-SD and CI were smaller under the LT condition than under the FR condition. No significant difference was observed in COP variables and CI under the DO condition between the young and elderly groups.ConclusionBoth young and elderly groups could decrease muscle co-contraction using the light fingertip contact. On the other hand, in the elderly group, COP variables showed a limited effect from the light fingertip contact; only the “sway” domain measure (AREA-SD). Both young and elderly groups showed the smallest CI under the DO condition. Therefore, the elderly group could decrease muscle co-contraction of the ankle joint depending on postural stability.

Modulation of soleus muscle H-reflexes and ankle muscle co-contraction with surface compliance during unipedal balancing in young and older adults

“…Presumably, older adults need more cortical control to cope with the same task in view of age-related changes in balance control mechanisms. Older adults are also known to display increased co-contraction in postural tasks (Iwamoto et al 2017), which may be caused by inadequate inhibition of antagonistic muscles leading to increased joint stiffness, possibly resulting in an increased susceptibility to fall (Tucker et al 2009). In contrast, increased cocontraction could be a compensatory strategy for impaired balance control (Kaplanski 2001), as it reduces delays in feedback control through pre-tensioning of muscle-tendon complexes (Oomen et al 2015).…”

Quantifying the Single Leg Balance Using Multiple Dynamic Postures on Stable Surface

“…There was a significant age dependent decrease in Unipedal Stance Time during both eyes open and eyes closed [16]. Adapting to various situations in exercise could make a margin to control a sudden unknown perturbation for elderly people [17]. Adaptations to SLB exercises could aid in maximizing fitness for healthy ageing by strengthening equilibrium reactions and inculcating confidence to efficiently move against gravitational force, perform the Activities of Daily Living (ADL) and tackle the risky perturbations in various situations at any age, especially during the ageing process.…”

Relationship between Speed of Response Inhibition and Ability to Suppress a Step in Midlife and Older Adults

“…Similarly, a general stiffening response (i.e., co-contraction) at the ankle joint would go undetected using TA alone. Co-contraction is a common finding in older adults performing postural tasks [38][39][40], and this may compromise response flexibility [41,42]. For example, co-contraction may impose a challenge to the motor system if excessive antagonist activation at the ankle joint must be first overcome to allow step initiation.…”