Inhibition of soleus Hoffmann reflex by ankle-foot orthosis application in healthy volunteers

Effects of orthoses on muscle activity and synergy during gait

An orthosis is often used in rehabilitation to improve kinetic and kinematic parameters during gait. However, whether changes in neural control depend on wearing an orthosis during gait is unclear. We measured the muscle activity and synergy of the lower limb muscles without orthosis and with two types of orthoses: ankle-foot orthosis (AFO) and knee-ankle-foot orthosis (KAFO). Muscle activity during gait was measured in 15 healthy adults, and muscle synergies were extracted using non-negative matrix factorization. The results revealed that some muscle activities were significantly different among the three conditions. Post-hoc analysis indicated differences between each condition. Knee extensor muscle activity related to the loading response was significantly increased by wearing the AFO. In the KAFO condition, hip abductor muscle activity related to weight bearing was significantly decreased, and ankle dorsiflexor muscle activity was increased to secure clearance during the swing phase. However, the number of muscle synergies and complexity of muscle synergy did not significantly change among these conditions. However, along with changes in muscle activity, the activation pattern and weightings of muscle synergies tended to change with the use of orthoses. Each muscle activity was changed by wearing the orthosis; however, the immediate mechanical constraint did not change the framework of muscle synergy.

Immediate effects of wearing knee length socks differing in compression level on postural regulation in community-dwelling, healthy, elderly men and women

BACKGROUND

Stimulation of lower limbs' cutaneous receptors and mechanoreceptors through compression garments could potentially increase somatosensory system efficiency and aid postural regulation in elderly individuals.

RESEARCH QUESTION

This study examined immediate effects of wearing knee length socks (KLS) of various compression levels on somatosensory function in community-dwelling healthy elderly men and women during a double-limb standing, balancing task.

METHODS

A total of forty-six elderly participants (Male = 23), aged between 65 and 84 years old, randomly selected from the Singapore community-dwelling, healthy population. Three treatment interventions (wearing clinical compression socks; wearing non-clinical compression socks; wearing commercial socks) and one control condition (barefoot), in a counterbalanced order, were administered to participants while they performed a 30-s Romberg test, with four levels of performance difficulty: (1) standing on a stable surface with vision (SO); (2) a stable surface without vision (SC); (3) a foam surface with vision (FO); and (4), a foam surface without vision (FC).

RESULTS

Results showed that immediate effects of applying KLS of various compression levels significantly reduced sway area, trace length, velocity, and anterior-posterior (AP) sway as compared to barefoot condition (control) during the FO task condition.

SIGNIFICANCE

This finding indicates the positive immediate effects of garments on somatosensory system function and postural regulation in the elderly men and women, especially when standing on the unstable surface. Wearing compression KLS could be included as a viable intervention on top of other forms of balance training to reduce risk of falling in elderly people.