Lower leg swelling and muscle co-contraction during prolonged standing: an unstable footwear evaluation

The purpose of this study was to investigate the lower leg swelling and muscle co-contraction during prolonged standing
with the focus on unstable footwear effects. The EMG signals of medial gastrocnemius and tibialis anterior muscles
(bilaterally) were continuously recorded to quantify their co-contraction index (CCI) in 10 healthy asymptomatic subjects
during two hours of standing in three footwear conditions including barefoot, stable shoe and unstable shoe. Lower leg
circumference changes (swelling) were also monitored over the standing time. During two hours of standing remarkable
reduction in lower leg circumference changes and significant reduced CCI level for both legs were observed only for
unstable shoe compared to barefoot condition. However, bilaterally, no significant differences were found for both
measures between barefoot condition and stable shoe or between two shoe conditions (stable and unstable). The unstable
shoe produced changes in activity pattern of lower leg muscles which seems to be advantageous for venous pump
mechanism during prolonged standing. These findings suggest that unstable footwear can be used as ergonomic
intervention for prolonged standing during work or daily activities