pISSN 2288-6982
eISSN 2288-7105




Phys. Ther. Korea 2017; 24(4): 46-53

Published online October 31, 2017

© Korean Research Society of Physical Therapy

Comparison of the Foot Muscle EMG and Medial Longitudinal Arch Angle During Short Foot Exercises at Different Ankle Position

Hyeo-bin Yoon1, Ji-hyun Kim1, Joo-hee Park1, and Hye-seon Jeon2,3

1Department of Physical Therapy, The Graduate School, Yonsei University,
2Department of Physical Therapy, College of Health Science, Yonsei University,
3Department of Ergonomic Therapy, The Graduate School of Health Science, Yonsei University

Correspondence to: Corresponding author : Hye-seon Jeon

Received: October 12, 2017; Revised: October 12, 2017; Accepted: November 11, 2017



The MLA is supported by both the abductor hallucis (ABH) and the extrinsic muscles. Insufficient muscular support may lower the MLA when the body’s weight is applied to the foot. The short foot exercise (SFE) is effective in increasing the height of the MLA for people with flat feet. Most of the research related to the SFE has simply evaluated the efficiency of the exercise using enhanced ABH electromyography (EMG) activation. Since the tibialis anterior (TA), peroneus longus (PER), and ABH are all involved in supporting the MLA, a new experiment design examining the EMG of the selected muscles during SFE should be applied to clarify its effect.


Therefore, this study aimed to clarify the effect of the SFE in different ankle position on the MLA angle and the activation of both the intrinsic and extrinsic muscles and to determine the optimal position.


20 healthy subjects and 12 subjects with flat feet were recruited from Yonsei University. The surface EMG and camera were used to collect muscle activation amplitude of TA, PER, and ABH and to capture the image of MLA angle during SFE. The subjects performed the SFE while sitting in three different ankle positions—neutral (N), dorsiflexion (DF) at 30 degrees, and plantar flexion (PF) at 30 degrees.


ABH EMG amplitudes were significantly greater in N and DF than in PF (p<.05). Muscle activation ratio of TA to ABH was the lowest in PF (p<.05). MLA angle in both groups significantly decreased in PF (p<.01). The TA and ABH was activated at the highest level in DF. However, in PF, subjects significantly activated the ABH and PER with relatively low activation of TA.


Therefore, researchers need to discuss which SFE condition most effectively use the arch support muscle for flat foot.

Keywords: Flat foot, Medial longitudinal arch, Short foot exercise.