Myoelectric Activity of Selected Trunk Muscles Following the Use of Various Insole Wedges During Running

Abstract

Purpose

Insoles with various wedges have effects on the biomechanical aspects of human movement. The aim of the present study was to investigate the immediate effects of 9 insoles while running on the myoelectric activity of selected trunk muscles. The conditions were no wedge, posterior, anterior, medial, lateral, posterior-medial, posterior-lateral, anterior-medial, and anterior-lateral. Muscles included were rectus abdominis, external oblique, internal oblique, latissimus dorsi, thoracic erector spinae, lumbar erector spinae, multifidus, and quadratus lumborum during running.

Methods

Twenty-five (n = 25) able-bodied males participated in this quasi-experimental study. Repeated measures analysis of variance test was used to compare dependent variables among various insole wedges.

Results

Significant differences (P = 0.001) in normalized mean amplitude index between the following wedge conditions were measured while running: posterior-lateral/medial (5.67 ± 1.01 vs. 4.73 ± 1.09) and posterior-lateral/anterior-medial (5.67 ± 1.01 vs. 4.52 ± 1.20) for the internal oblique muscle along with posterior-lateral/anterior (11.44 ± 2.42 vs. 9.26 ± 2.35) for the lumbar erector spinae muscle. Similarly, normalized peak amplitude index differences in the medial/anterior-lateral (9.79 ± 3.33 21 vs.12.03 ± 3.16) and lateral/anterior-medial (11.6 ± 2.56 vs. 9.25 ± 2.38) for the internal oblique muscle and posterior-lateral/anterior-medial (9.58 ± 2.26 vs. 8.78 ± 2.15) for the quadratus lumborum muscle were measured. In contrast, no significant difference was observed for the median frequency index among various insole wedges during running (P > 0.0014).

Conclusion

Decreased activity in the medial wedged conditions may have important negative consequences for the spine, pelvis, and dynamic core. These results provide insights into the effect of various orthotic designs on the EMG activity of central core muscles. Higher activation in an anterior-lateral wedge and lower activation in a medial wedge for core muscles can have clinical relevance, where there is a need to increase, or avoid decrease, core muscle activity.