Effects of unstable shoes on trunk muscle activity and lumbar spine kinematics

In patients with neuromuscular disease and a forced vital capacity (FVC) of <30% of the predictive value, scoliosis correction operation was Background. An unstable shoe was developed as a walking device to strengthen the lower extremity muscles and reduce joint loading. A large number of studies have reported increased electromyographic (EMG) activity throughout the gait cycle in most of the lower limb muscles, and significant kinematic changes in the lower extremity. However, no studies have investigated the effects of wearing unstable shoes on spine kinematics and trunk muscle activity during gait.

To compare trunk muscle activity and lumbar spine range of motion (ROM) during gait using an unstable shoe and a conventional stable control shoe.

Cross-sectional study.

A Biomechanics laboratory.

Forty-eight healthy voluntary participants (24.5±5.6 years and 22.7±6.8 kg/m2).

Subjects underwent gait analysis while simultaneously collecting surface EMG data of erector spinae (ES) and rectus abdominis (RA) and lumbar spine sagittal plane ROM while treadmill walking wearing regular shoes and unstable shoes.

The results showed that the unstable shoes resulted in significantly higher ES and RA EMG muscle activity levels in all gait phases compared to control shoes (P<0.001). In addition, the unstable shoe condition showed a significantly higher mean (mean difference: 3.1º; 95% CI 2.2º to 4º) and maximum (mean difference: 4.5º; 95% CI 2.6º to 6.5º) lumbar spine extension values (P<0.001).

Unstable shoes increase trunk muscle activity (ES, RA) and lumbar lordosis during gait compared to control shoes.

Based on these findings, the use of unstable shoes may have potential implications in promoting spine tissue health, particularly in strengthening trunk muscles in healthy population or in low back pain treatment.