Effect of Aging on Feasibility and Contribution of Joint Mechanisms in Balanced Standing Using Biomechanical Modeling

Reduced muscle strength due to aging may adversely affect the ability of the body in postural balance.
The aim of the present study was to numerically investigate the effects of aging on muscle recruitment patterns in keeping the balance during static standing posture.
In this numerical study, a total of 4096 static postures were considered by changing in the angles of three lower limb joints i.e. ankle, knee and hip in two complete human musculoskeletal models of young and old body with 44 muscles in the leg. Inverse dynamics approach was used to find the muscle activation in all postures. The joint mechanisms were assessed by considering the ratio between related muscle activities to the total activation.
Results showed that the muscle efforts in both models were posture-dependent and the knee played a relieving role specifically for the aged model. The possible postures that the young person could provide balance was wider than the elders. Also, the aged model expended more effort in doing the same tasks. The muscles revealed distinct joint mechanisms in the young model in contrast to the elders which used higher but non-distinguishable joint mechanisms.
Collaboration between the joint mechanisms was higher in the aged model but the young could more rely on individual mechanisms during static postural balance.