This study evaluates the effectiveness of the Zoles customised 3D-printed insoles to mitigate running-related pain among frequent recreational runners who participate in regular Park Run activities. All participants will have their feet scanned, after which half of the participants will be provided with customised 3D-printed insoles, while the other half will receive no intervention.

The ZOLES trial is a pragmatic, outcome assessor blinded, randomised, controlled, superiority trial, with a two-group parallel design. Frequent recreational runners who participate in regular Park Run activities will undergo a foot scanning after which they will be randomised in a 1:1 allocation ratio to either receive a customised 3D-printed insole (Zoles ApS, Espergærde, DK-3060, Denmark), or to be in a "do-as-usual" control group. It is expected that the allocated intervention group participants will have received their customised insoles around two weeks after baseline during the follow-up period (one week to manufacture, one week to distribute). The primary endpoint is change in running-related pain 10 weeks after baseline (∼8 weeks after receiving allocated intervention).

A full trial protocol, based on the "SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials" and the "PREPARE Trial guide", will be published and made publicly available. The trial report will follow the "REPORT guide", and thus adhere to the CONSORT guidelines for reporting parallel group randomised trials, using the CONSORT extension for pragmatic trials, as well as the updated CONSORT-Outcomes 2022 extension. The TIDieR template is used to describe the intervention to aid future replication.

The central aim of this study is to establish the effectiveness of the Zoles customised 3D-printed insoles in alleviating running-related pain among frequent recreational runners participating in regular Park Run activities when compared against a "do-as-usual" control group. This clinical effectiveness will be reported in the main trial paper, which also includes the following key secondary outcomes: Global Rating of Change (GRoC) in overall daily pain and discomfort, Running-related foot/footwear comfort, 5-k (Park Run) completion time, running-related injury incidence rate, Time-loss from running, running exposure in miles and time, adherence to the intervention during daily- and running activities, and adverse events from using the Zoles insoles. Missing values will be imputed using multiple imputations by chained equations based on the following variables: All previous scores within the relevant outcome category, Age, Sex, Group Allocation, and enrolment (Park Run) location.

A total of 200 participants are anticipated to be enrolled, resulting in a minimum of 100 participants in each arm. The enrolment concludes once at least 100 participants have been allocated to each arm. Being a pragmatic trial, the eligibility criteria are loosely defined such that participants should simply be regular runners engaged in frequent Park Run activities, at a minimum 35 years of age. The participants will undergo balanced block randomization (1:1 allocation ratio), ensuring stratification for sex and enrolment location. The trial will include prospective weekly data collection using e-mail-distributed surveys via REDCap (Vanderbilt University, Nashville, TN, USA) throughout the 10-week follow-up period. After the conclusion of the initial 10-week trial phase, the control group will also be provided with their customised 3D-printed insoles. This will not be weekly monitored, however, following an additional 8-week period with the insoles, this group will then complete the follow-up questionnaire again, to ascertain whether similar benefits or deterioration from the insoles in a manner consistent with the original experimental group are experienced. At the conclusion of the trial, and as part of a post-market surveillance approach, all participants, both from the original experimental and control groups (who by this point have received the intervention), will be administered a final questionnaire after a 1-year period to evaluate the long-term effects and durability of the benefits associated with the customised 3D-printed insoles.

The primary outcome; change in running-related pain from baseline to follow-up, will be calculated using negative binomial regression, adjusting for values reported at baseline. Both the Global Rating of Change (GRoC) in overall daily pain and discomfort, and Running-related foot/footwear comfort will be calculated similarly. Injury incidence rate ratios will be estimated per 1000 hours of running exposure using Poisson regression. Mean time-loss from running will be calculated using negative binomial regression. Adherence to the intervention will be descriptively analysed and presented, and adverse event due to the Zoles insoles will be presented in type and frequency. Every analysis in the main trial report will abide by the intention to treat principle, which means including all participants in the analyses, regardless of intervention adherence-signifying that participants will be analyzed based on initial randomization. In the primary trial report, all collected outcomes will be listed, and it will also be stated that the below-mentioned 'other pre-specified outcomes' will be reported in a subsequent secondary analysis publication with a clear reference to the primary trial registration.

The subsequent secondary analysis publication will hold the label "secondary and long-term follow-up analysis from a pragmatic randomized controlled trial" in the title. The aims of this secondary subgroup analysis study are two-fold: First, it is to investigate the immediate therapeutic effect of Zoles insoles, focusing only on participants with clinically relevant baseline pain levels (11-NRS ≥ 3). Secondly, this will include our long-term post-market analysis to evaluate the long-term effects and durability of the benefits associated with the customised 3D-printed insoles one year post-intervention. In the secondary subgroup analysis, the following outcomes will be reported: Percentage of participants achieving a change of at least MCID (11-NRS ≥ 2) in running-related pain, Time until change in running-related Pain of at least MCID, Change among participants with clinically relevant running-related pain at baseline, Pre-trial expectations to the therapeutic effect of using the Zoles insoles, and Post-trial experiences on the therapeutic effect of using the Zoles insoles. Incorporating the expectations and post-intervention experiences as covariates, regression models will be constructed to understand the potential influence of these factors on the efficacy of the Zoles insoles intervention within this specific subgroup of participants.

Inclusion Criteria:

• Participant is ≥ 35 years old at commencement of trial
• Participant can read, speak and understand English
• Participant can receive e-mails and complete online questionnaires
• Participant is a frequent runner who participate in regular Park Runs
• Participant is capable of running at commencement of trial

Exclusion Criteria:

• Individuals with severe foot deformities
• Individuals with uncontrolled diabetes with foot complications, or other conditions that might interfere with their ability to safely use the insoles and participate in running activities