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Tuesday, June 6, 2023

Effect of Foot Orthoses on Tibialis Posterior Activation in Persons with Pes Planus

Brent Brookbush

Brent Brookbush


Research Review: Effect of Foot Orthoses on Tibialis Posterior Activation in Persons with Pes Planus

By Julie Randall PT, LMT, MBA

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Kulig, K., Burngield, J. M., Reischl, S., Requejo, S. M., Blanco, C. E., and Thordarson, D. B. (2005). Effect of foot orthoses on tibialis posterior activation in persons with pes planus. Medicine and science in sports and exercise, 37(1), 24-29 - Abstract

Why the Study Is Relevant: The tibialis posterior is a strong invertor and supinator of the foot (1), and dysfunction has been correlated with collapse of the medial longitudinal arch (pes planus) (2, 3). Common conservative treatments include strengthening and orthotics (2-6). This 2005 study investigated the effect of shoes and orthotics on tibialis posterior activation while performing resisted foot adduction exercise. The findings suggest that shoes and orthotics enhanced tibialis posterior activation when compared to the same exercise performed barefoot/sham orthotic.

Example of a "Full Foot" custom Orthotic
Caption: Example of a "Full Foot" custom Orthotic

Example of a "Full Foot" custom Orthotic

Study Summary

Study Design Cross-over design without randomization
Level of Evidence IIA Evidence from at least one controlled study without randomization
Subject Characteristics

6 asymptomatic adults


  • Age (y): 25.0 ± 2.0
  • Gender: not provided
  • Mass (kg): 71.7 ±7.7
  • Height (cm): 1.778  ± 0.076
  • Average Arch Index: 0.146 ± 0.014

Inclusion Criteria:

  • Arch index of at least two standard deviations below normative values (≤0.16)

Exclusion Criteria:

  • Orthopedic or neurological disorders that prevented subjects from completing the exercise protocol
  • Subjects who had contraindications or precautions to having an MRI
  • Testing took place in two sessions, one week apart.
  • MRI scanning pre and post exercise to determined the intensity of muscle activation in the lower leg.
  • In session one, participants performed the resisted foot adduction barefoot.
  • In session two, participants performed resisted foot adduction wearing shoes and a full-length foot orthoses to correct the arch.
  • In both sessions, 3 sets of 30 repetitions were completed with a 1 minute inter-set rest period.
Data Collection and Analysis

The change in signal intensity, pre and post-exercise, was determined using the equation:

[(SNRpost-SNRpre)/SNRpre] x 100

SNR=signal intensity

Post = post-exercise value

Pre = pre-exercise value

  • One investigator analyzed all MRI data.
  • Signal intensity with an increase of > 10% indicated an active muscle.
  • Percent change in signal intensity pre- and post- exercise was measured for both barefoot and shoe/orthoses sessions.
  • Test significance was measured using an alpha level of 0.5 Post hoc t-tests were utilized as needed.
Outcome Measures The means and standard errors of the mean change in signal intensity for each muscle (tibialis posterior, tibialis anterior, soleus, medial gastrocnemius, peroneus longus) was illustrated on a bar chart comparing data from session one and two.
Results The tibialis posterior  increased in signal intensity during both sessions.
  • 29% in session 1 (barefoot)
  • 54% in session 2 (with shoes and orthoses)

The remaining four muscles did not show as consistent a change for either session.

  • Inconsistent changes were seen in session 1 (barefoot)
  • Less than 10% significance threshold was obtained during session 2 (with shoe/orthoses).
Our ConclusionsIndividuals exhibiting lower extremity dysfunction may enhance tibialis posterior muscle activation by wearing shoes and foot orthoses (when prescribed by a licensed professional) during activation exercises.
Researchers' Conclusions

 Individuals with pes planus can most effectively activate the tibialis posterior muscle with resisted foot adduction by wearing shoes and orthoses.

Dr. Brent Brookbush instructs a patient on how to perform Tibialis Posterior Activation with toe extension to reciprocally inhibit the long toe flexors.
Caption: Dr. Brent Brookbush instructs a patient on how to perform Tibialis Posterior Activation with toe extension to reciprocally inhibit the long toe flexors.

Tibialis Posterior Activation

Review & Commentary:

This study adds to a growing body of research investigating conservative treatment approaches for pes planus and tibialis posterior dysfunction (2-6). It has been asserted that orthotic insoles may act as a crutch, reducing the need for tibialis posterior activation and force production during functional tasks. This in turn leading to atrophy, under-activity and weakness over time. However, this study demonstrates that the opposite conclusion may be true. Wearing shoes and orthotic insoles enhanced the selective recruitment of the tibialis posterior during activation exercises .

This study had many methodological strengths, including:

  • The same examiner reviewed all MRI findings for each session, maintaining consistency.
  • Signal intensity of the muscles was measured with Magnetic Resonance Imaging (MRI). If this and other studies demonstrate reliability, this non-invasive method may prove useful for investigating deeper muscles, or muscles in groups of individuals in which fine wire (intra-muscular) electromyography (EMG) would not be advisable.
  • A prior study has shown that the foot adduction exercise is effective for recruiting the tibialis posterior (5). The use of this effective, easy to perform exercise enhances the clinical relevance of the study.
  • The inclusion of MRI signal intensity for the tibialis anterior , soleus , medial gastrocnemius , peroneus longus demonstrated that orthotics also reduced the recruitment of other musculture, showing a change in recruitment strategy at the ankle as well as an increase in tibialis posterior strength.

Weakness and limitations:

  • The low number of participants (6) reduces the statistical power of the results. Future studies should include a larger sample size and/or different methodological approaches to measuring tibialis posterior muscle activation.
  • As a small study, perhaps limited by the cost of MRI analysis, the study lacked a control group and/or randomization.
  • The use of asymptomatic individuals may reduce the generalizility of the study to a patient populations with complaints of foot pain.

Why This Study Is Important:

Conflicting ideas and hypotheses have circulated regarding the long-term, therapeutic use of orthotic insoles. While the immediate reduction in symptoms and positive alterations in mechanics are an obvious benefit, the long-term effect on muscle activity, strength and/or atrophy was a legitimate concern worth further investigation. This study adds to a growing body of research that shows orthotic insoles may aid in selective recruitment of invertors and improve muscle activity and strength when used in conjunction with therapeutic exercise.

How the Findings Apply to Practice:

This study showed a 54% increase over baseline activity in tibialis posterior muscle activity when participants wore shoes/orthoses versus a 29% increase when the exercise was performed barefoot. These findings suggest that human movement professionals should instruct patient/client's to keep their shoes and orthotic insoles on while performing tibialis posterior activation exercises .

How does it relate to Brookbush Institute Content?

This study addresses the tibialis posterior with strengthening exercises, as recommended by the Brookbush Institute (BI) in the articles Tibialis Posterior Activation and Lower Extremity Dysfunction (LED) . In the majority of the tibialis posterior exercises described and demonstrated on video in those articles, adduction (a combination of inversion and medially directed force) is recommended, but exercises were done without shoes on for demonstration purposes (so the toes and inversion of the foot can be clearly seen on video). This study suggests that shoes and orthotic insoles (when prescribed by a licensed professional) should be promoted during these exercises. Below are a few examples of Tibialis Posterior Activation :

Tibialis Posterior Activation Progression 1:

Tibialis Posterior Activation Progression 2:

Tibialis Posterior Activation Progression 3:

Tibialis Posterior Activation Progression 4:


  1. Klein, P., Mattys, S., & Rooze, M. (1996). Moment arm length variations of selected muscles acting on talocrural and subtalar joints during movement: An in vitro study. Journal of biomechanics, 29(1), 21-30.
  2. Yao, K., Yang, T. X., & Yew, W. P. (2015). Posterior tibialis tendon dysfunction: overview of evaluation and management. Orthopedics, 38(6), 385-391.
  3. Alvarez, R. G., Marini, A., Schmitt, C., & Saltzman, C. L. (2006). Stage I and II posterior tibial tendon dysfunction treated by a structured nonoperative management protocol: an orthosis and exercise program. Foot & ankle international, 27(1), 2-8.
  4. Kohls-Gatzoulis, J., Angel, J.C., Singh, D., Haddad, F., Livingstone, J., & Berry, G. (2004). Tibialis posterior dysfunction: a common and treatable cause of adult acquired flatfoot. BMJ: British Medical Journal, 329(7478), 1328.
  5. Kulig, K., Burnfield, J. M., Reischl, S., Requejo, S.M., Blanco, C.E., & Thordarson, D.B. (2005). Effect of foot orthoses on tibialis posterior activation in persons with pes planus. Medicine and science in sports and exercise, 37(1), 24-29.
  6. Kulig, K., Burnfield, J. M., Requejo, S. M., Sperry, M., & Terk, M. (2004). Selective activation of tibialis posterior: evaluation by magnetic resonance imaging. Medicine and science in sports and exercise, 36(5), 862-867.

© 2017 Brent Brookbush

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