Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

Abstract

Purpose: This study investigated the influence of long-term wearing of unstable shoes (WUS) on compensatory postural adjustments (CPA) to an external perturbation.Methods: Participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8 weeks. The ground reaction force signal was used to calculate the anterior-posterior (AP) displacement of the centre of pressure (CoP) and the electromyographic signal of gastrocnemius medialis (GM), tibialis anterior (TA), rectus femoris (RF) and biceps femoris (BF) muscles was used to assess individual muscle activity, antagonist co-activation and reciprocal activation at the joint (TA/GM and RF/(BF+GM) pairs) and muscle group levels (ventral (TA+RF)/dorsal (GM+BF) pair) within time intervals typical for CPA. The electromyographic signal was also used to assess muscle latency. The variables described were evaluated before and after the 8-week period while wearing the unstable shoes and barefoot. Results: Long-term WUS led to: an increase of BF activity in both conditions (barefoot and wearing the unstable shoes); a decrease of GM activity; an increase of antagonist co-activation and a decrease of reciprocal activation level at the TA/GM and ventral/dorsal pairs in the unstable shoe condition. Additionally, WUS led to a decrease in CoP displacement. However, no differences were observed in muscle onset and offset. Conclusion: Results suggest that the prolonged use of unstable shoes leads to increased ankle and muscle groups' antagonist co-activation levels and higher performance by the postural control system.

Influence of prolonged wearing of unstable shoes on upright standing postural control

“…Finally, because these postural control adaptation strategies lead to reduced noise and increased accuracy (Lacquaniti et al, 1993), a decreased postural control system error, demonstrated through the CoM and CoP relation (Winter, 1995a) (RM and TR (Zatsiorsky & Duarte, 2000)) can also be expected. after prolonged use of the shoes, as no differences were previously demonstrated during compensatory postural adjustments in response to an external perturbation (Sousa et al, 2013a;Sousa et al, 2013b). Also, the results obtained in these studies support the hypothesis of a decreased co-activation command in the unstable shoe condition compared to barefoot.…”

“…Indeed, the results of this study reveal that prolonged wearing of the unstable shoes led to a large effect in the increase of thigh antagonist co-activation. A transfer of postural control synergy for the thigh has been demonstrated in compensatory responses after a 8 weeks period of wearing unstable shoes (Sousa et al, 2014) and has been reported as more beneficial to optimise postural stability (Day et al, 1993;Horak et al, 1990;Kuo, 1993;Runge et al, 1999;Yang et al, 1990). This association is corroborated not only by the decrease of the most representative CoP displacement parameters and RM P-P, but also by decreased anterior-posterior TR RMS.…”

“…Also, the results of the present study indicate that, in both pre-and post-training, wearing unstable shoes leads the postural control system to rely more on reciprocal activation than on co-activation to compensate for the decreased stability compared to barefoot. This has been demonstrated to be more efficient and accurate, but also more challenging for the postural control system (Aruin & Almeida, 1997;Friedli et al, 1984;Garland et al, 1997;Hogan, 1984;Hong et al, 1994;Latash et al, 1995;Massion et al, 1999), and it has been observed also in compensatory postural adjustments in response to an external perturbation (Sousa, et al, 2013a;Sousa, et al, 2014). These findings demonstrate that wearing unstable shoes is more demanding in terms of postural control than barefoot, but lead to a higher efficiency and accuracy in postural commands.…”

“…More explicitly, the purposes were to evaluate the effect of wearing unstable shoes on: 1) CoP displacement pattern, 2) CoP and CoM inter-relation through RM and TR components, 3) total agonist and antagonist muscle activity, and 4) agonist-antagonist muscle relation. Based on recent studies which have demonstrated that wearing unstable shoes improves the performance of postural control responses to external perturbations (Sousa et al, 2013a;Sousa et al, 2013b), it can be hypothesised that the long-term wearing of unstable shoes would lead to higher performance and effectiveness of upright standing postural control, reflected by decreased CoP displacement, area and velocity (Bennell & Goldie, 1994;Kinzey, et al, 1997;Norris et al, 2005) and dispersion (Prieto et al, 1996), respectively. Also, considering that the postural control system relies more strongly on co-activation commands at the beginning of learning (Feldman, 1980a;Flash, 1987;Serres & Milner, 1991), when the internal models are poor, and on reciprocal activation commands as the learning proceeds (Imamizu et al, 2000;Osu et al, 2002), increased reciprocal activation and decreased antagonist co-activation after prolonged wearing of unstable shoes can be hypothesised.…”

An Overview of Smart Shoes in the Internet of Health Things: Gait and Mobility Assessment in Health Promotion and Disease Monitoring

“…Other applications also address gait signature analysis. For example, IMMUs are used to determine joint stress in barefoot running [64], landing patterns [30] and vertical loading [29,30,35,45,[65][66][67][68], loading while running barefoot [69], the effects of a high-heeled gait [70], the effects of rollover footwear [71], and the influence of the long-term wearing of unstable shoes [67].…”