How do foot-ankle exercises improve clinical and plantar pressure outcomes in people with diabetic peripheral neuropathy? A mediation analysis of a randomized controlled trial

Abstract

Background

Foot-ankle exercises targeting modifiable risk factors, such as peak pressure, ankle motion, and foot strength, may reduce ulcer risk and improve gait biomechanics, but the pathways driving these improvements are unclear.

Objectives

To identify the causal pathways through which a 12-week foot-ankle exercise program improved foot function, pain, and plantar pressure during gait by examining key mediators of these effects.

Methods

A total of 62 participants with diabetic peripheral neuropathy (DPN) were assigned to either a web-based foot-ankle program or usual care. The outcomes included peak pressure, pressure–time integral at the forefoot, foot pain, and foot function. Mediators included hallux and toe strength, sagittal ankle range of motion (ROM) during gait stance phase, ankle plantar flexion angle at push-off, ankle extensor moment at push-off, and foot pain and function. Outcomes and mediators were assessed at baseline, 12 weeks, and 24 weeks. Mediation models were tested using ordinary least squares regression with bias-corrected bootstrap confidence intervals.

Results

The analysis revealed consistent and inconsistent mediation effects. Improvements in foot function were mediated by reductions in foot pain (1.71, 95 % CI: 0.21, 4.43) and increases in ankle plantar flexion angle at push-off (0.45, 95 % CI: 0.15, 0.74). While the intervention directly reduced forefoot peak pressure, inconsistent mediation occurred, with indirect increases through reduced foot function (3.84, 95 % CI: 1.04, 11.38). Consistent mediation was observed, with increased sagittal ankle ROM during gait stance phase (9.02, 95 % CI: 2.47, 17.68) mediating a rise in the forefoot pressure-time integral.

Conclusion

The program reduced pain, improved function, and influenced plantar pressure through mediated pathways, highlighting a complex interplay of consistent and inconsistent mediation effects.