Evidence of intrinsic foot muscle training in improving foot function: a systematic review and meta-analysis

Key points

1. 01IFM exercises reduced navicular drop (SMD 1.10, 95% CI 0.37-1.83) and Foot Posture Index (SMD 1.36, 95% CI 1.03-1.60) compared with controls.
2. 02Dynamic balance improved with IFM training (SMD 1.02, 95% CI 0.18-1.86), though two individual studies showed no balance benefit.
3. 03Toe flexor strength improved significantly (SMD 0.79, 95% CI 0.06-1.26) with IFM exercise versus control.
4. 04Self-reported disability decreased with IFM training (SMD 0.56, 95% CI 0.12-1.00), but pain scores did not improve (SMD 0.25, 95% CI -0.15-0.66, P=.22).
5. 05The short foot exercise was the most commonly used and most consistently effective IFM exercise across included studies.

How it was conducted

Design

Systematic review and meta-analysis of randomized controlled trials

Studies included

13 RCTs identified from PubMed, CINAHL, Scopus, and SPORTDiscus (January 2000 to March 2022)

Participants

Adults across clinical groups (pes planus, chronic ankle instability, patellofemoral pain, plantar fasciitis) and healthy populations

Intervention

Intrinsic foot muscle strengthening exercises (minimum 2 weeks), most commonly the short foot exercise

Primary outcomes

Foot posture (navicular drop, Foot Posture Index), balance, strength, patient-reported pain and disability, sensory function, motor performance

Quality assessment

PEDro scale; only studies scoring greater than 4/10 included; random-effects meta-analysis with SMDs and 95% CIs

What they found

• Navicular drop: pooled SMD 1.10 (95% CI 0.37-1.83), P<.01, I2=80%, favoring IFM exercise over control (5 studies).
• Foot Posture Index: pooled SMD 1.36 (95% CI 1.03-1.60), P<.01, I2=0%, favoring IFM exercise (4 studies).
• Dynamic balance: pooled SMD 1.02 (95% CI 0.18-1.86), P<.01, I2=83%, favoring IFM exercise (5 studies).
• Toe flexor strength: pooled SMD 0.79 (95% CI 0.06-1.26), P<.01, I2=21%, favoring IFM exercise (2 studies).
• Disability (patient-reported): pooled SMD 0.56 (95% CI 0.12-1.00), P=.01, I2=0%, favoring IFM exercise (2 studies).
• Pain (patient-reported): pooled SMD 0.25 (95% CI -0.15-0.66), P=.22, I2=0%; no significant improvement over control (2 studies).
• Sensory function (1 study): SMD 2.27 (95% CI 1.35-3.19) in intervention group vs SMD 0.69 (95% CI -0.05-1.43) in control group.
• Motor performance (1 study): SMD 1.40 (95% CI 0.77-2.03) in intervention group vs SMD 0.00 (95% CI -0.63-0.63) in control group.

Limitations

• Healthy and clinical populations were pooled in the meta-analyses, which may obscure group-specific effects.
• High heterogeneity was present for navicular drop (I2=80%) and balance (I2=83%) outcomes, reflecting variation in exercises, durations, and populations.
• Only 1 study each reported sensory function and motor performance outcomes, so meta-analysis was not possible for these domains.
• The variety of IFM exercise types, intensities, and intervention durations limits conclusions about optimal dosing.

Why it matters

For patients

People with flat feet, ankle instability, or patellofemoral pain may benefit from adding short foot exercises to their rehabilitation to improve balance and reduce perceived disability, though direct pain relief is unlikely from IFM training alone.

For clinicians

Clinicians should consider prescribing intrinsic foot muscle exercises, especially the short foot exercise, as part of lower extremity rehabilitation programs, with realistic expectations that disability and functional outcomes improve but pain may not.

For readers

This is the first comprehensive meta-analysis on IFM training, providing moderate-quality evidence that these exercises improve multiple functional outcomes, though the evidence base is still small and heterogeneous in several domains.