Effectiveness of customised 3D-printed insoles on pain, comfort, and completion time among frequent parkrun™ participants: a pragmatic randomised controlled trial

Introduction
Recreational runners often experience pain and discomfort, impacting their performance and participation. ZOLES are novel 3D-printed insoles designed from individual anthropometric data and foot morphology. This study aimed to evaluate the effectiveness and safety of ZOLES insoles in reducing pain and increasing foot-footwear comfort among recreational parkrun™ participants.

Materials and Methods
In this parallel group randomised controlled trial (NCT06034210; protocol published, PMID: 38350194), 210 recreational runners (age ≥35) were randomised 1:1 to receive ZOLES 3D-printed insoles or a ‘do-as-usual’ control group. The primary outcome was running-related pain, measured weekly over 10 weeks using 11-point numeric rating scales, and analysed with intention-to-treat. Secondary outcomes included Global Rating of Change (GRoC), foot-footwear comfort, 5k completion time, and adverse effects.

Results
208 participants completed the trial (99 ZOLES, 109 control) with a weekly response rate of 98.9%. Baseline pain scores were similar between groups (2.91 vs. 3.03). Both groups experienced reductions in pain: -1.42 points (95% CI: −1.88, -0.94) in the ZOLES group and -0.98 points (95% CI: −1.37, -0.58) in the control group, with a non-significant between-group difference of -0.44 points (95% CI: −1.04, 0.17; p=0.095). More participants in the ZOLES group reported overall improvement (GRoC) (43% vs. 24%; p=0.0059) and improved foot comfort (p=0.034). There was no difference in 5k completion times (p=0.463). Seven non-serious harms, mostly blisters, were reported.

Conclusion
ZOLES 3D-printed insoles did not significantly reduce running-related pain, despite a higher rate of perceived overall improvement and improved foot-footwear comfort. 5k-parkrun™ times were unaffected, and only minor adverse events were reported.