The Effectiveness of Customised 3D-printed Insoles on Perceived Pain, Comfort, and Completion Time Among Frequent Park Runners: A Pragmatic Randomised Controlled Trial (The ZOLES Trial)
Phase: NA
Conditions: Pain
Sponsor: St. Mary's University, Twickenham

 
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The effectiveness of customised 3D-printed insoles on perceived pain, 
comfort, and completion time among frequent Park Runners: Study 
protocol for a pragmatic randomised controlled trial (The ZOLES RCT) 
Suleyman Ibrahim1, Chris Djurtoft2, Rik Mellor1, Kristian Thorborg3, Filip Gertz Lysdal1* 
1Faculty of Sport, Technology and Health Sciences, St Mary’s University, Waldegrave Rd, Twickenham, TW1 
4SX, London, United Kingdom 
2Center for General Practice at Aalborg University, Department of Clinical Medicine, Aalborg University, 
Fyrkildevej 7, DK-9220, Aalborg Ø, Denmark 
3Sports Orthopaedic Research Center–Copenhagen (SORC–C), Department of Orthopaedic Surgery, 
Copenhagen University Hospital, Amager-Hvidovre, Kettegård Alle 30, DK-2650, Hvidovre, Denmark 
Twitter/X: @FilipGertz @ChrisDjurtoft @KThorborg @RikMellor @sol_ibrahim23 
Emails: 
2213944@stmarys.ac.uk; 
cdjurt@dcm.aau.dk; 
rik.mellor@stmarys.ac.uk; 
Kristian.Thorborg@regionh.dk; filip.lysdal@stmarys.ac.uk 
 
Protocol Version 1, September 27, 2023. 
ClinicalTrials.gov identifier: NCT06034210 
 
 
*Corresponding author: 
Filip Gertz Lysdal 
Faculty of Sport, Technology and Health Sciences 
St Mary’s University 
Twickenham, London 
TW1 4SX 
United Kingdom 
Email: filip.lysdal@stmarys.ac.uk 
Phone: +45 2720 5197 
 
Competing interests 
No authors have any ethical or competing interests to declare in relation to this study. 
Word count: 6230 (Excluding title, abstract, figures, and reference list). 
Submitted to: The Foot 
 
October 2023 

 
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The effectiveness of customised 3D-printed insoles on perceived pain, 
comfort, and completion time among frequent Park Runners: Study 
protocol for a pragmatic randomised controlled trial (The ZOLES RCT) 
Abstract 
Background 
Running, a popular recreational activity, often leads to the experience of pain and 
discomfort among participants impacting performance and participation longevity. The 
ZOLES trial evaluates customised 3D-printed insoles for reducing pain in frequent 
parkrunners aged 35 and over. An innovative process of foot-scanning and responses to 
questions relating to size, pain, discomfort, and previous medical conditions are 
combined leading to the production of personalised 3D-printed orthotics. 
Methods 
The ZOLES trial is a pragmatic, outcome assessor blinded, randomised, controlled, superiority 
trial involving 200 recreational runners, randomised to receive either customised 3D-printed 
insoles (ZOLES) or to a "do-as-usual" control group. The study follows a robust protocol, 
ensuring adherence to established guidelines for clinical trials, and is based at St Mary’s 
University, Twickenham, London. The primary outcome is change in running-related pain over 
a 10-week period, assessed using an 11-NRS pain scale. Secondary outcomes include overall 
pain and discomfort, running-related comfort, 5k-completion time, time-loss due to injuries, 
running exposure, and adherence to the intervention. A balanced-block randomisation process 
is stratified by sex and parkrun location, and an intention-to-treat analyses will be employed 
on all outcomes in the primary trial report. The trial includes a 52-week post-market 
surveillance to assess long-term effects of the customised insoles.  

 
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Discussion 
The ZOLES trial aims to provide insights into real-world applicability and effectiveness 
of customised 3D-printed insoles in reducing running-related pain and enhancing overall 
running experience. Despite the limitation of a subjective primary outcome measure 
without participant blinding, the methodological rigor, including external outcome 
assessment and data handling, we anticipate results that are academically credible and 
applicable in real-world settings  The results of this trial may have important implications 
for runners, clinicians, and the sports footwear industry, as evidence for the use of 
individualised insoles to improve running experience and prevention of pain may become 
evident.  
Trial registration 
The trial was pre-registered at ClinicalTrials.gov with the trial identifier NCT06034210 on 
September 
4, 
2023, 
and 
publicly 
posted 
on 
September 
13, 
2023 
(https://clinicaltrials.gov/study/NCT06034210).  
Keywords 
pain [MeSH]; running [MeSH]; foot orthoses [MeSH]; quality improvement [MeSH]; 
parkrun 
Protocol version 
Version 1, September 27, 2023. 
Abbreviations1 
 
 
1 
TPU: Thermoplastic Polyurethane  
MCID: minimal clinical important difference 
NRS: Numeric Rating Scale 
GRoC: Global Rating of Change 
CG: Control Group 
IG: Intervention Group 
ITT: Intention-to-treat 
CONSORT: Consolidated standards of reporting trials 
SPIRIT: Standard protocol items: Recommendations for interventional trials 
TIDieR: Template for intervention description and replication 
FINER: Feasible, Interesting, Novel, Ethical, and Relevant 
REDCap: Research Electronic Data Capture 

 
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Background 
Engaging in regular physical activity, particularly running, is associated with numerous health 
benefits [1]. It can enhance cardiovascular health [2], improve weight management [3], mental 
well-being [4,5], and generally reduces all-cause mortality [6]. A testament to the growing 
popularity of running is the burgeoning 'parkrun' movement. Originating in Bushy Park outside 
of London in the UK, parkrun is a community-driven initiative that offers timed running events 
in parks around the world [7]. These events serve as an accessible and welcoming platform for 
individuals of all fitness levels to engage in running and cultivate an active lifestyle. Through 
this initiative, parkrun not only contributes to the individual health of participants but also 
fosters a global community that values physical activity and communal engagement [8]. 
However, the benefits of running do not come without risk of potential drawbacks. A 
significant portion of runners, both recreational and competitive, run with high levels of 
musculoskeletal pain (≥3 on 11-NRS) [9], and encounter musculoskeletal injuries, particularly 
in the lower extremities, at high rates [10]. Such setbacks not only result in time away from 
running [11] but can also cascade into reduced daily physical activity levels [12]. In some 
cases, persistent pain and recurring injuries may culminate in total inactivity [13], associated 
with a lower quality of life and ultimately elevating the risk of depression [14] and premature 
mortality [15]. 
Foot and footwear discomfort might increase this risk of injury [16], with a potential inverse 
relationship, whereby enhanced foot-footwear comfort might serve as a protective factor 
against running-related injuries [17]. Furthermore, greater comfort seems to correlate with 
improved performance in running [18]. Modern technological advancements, notably 3D 
printing, have recently refined the orthotic fabrication process, providing tailored support and 
cushioning that can be adapted to both foot shape and pressure distribution [19,20], with 
superior comfort compared to prefabricated insoles [21]. As is often the case, however, many 

 
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studies on biomechanical interventions, such as foot orthotics, never make it out of the 
laboratory [22], or the trials are conducted on specific subgroups with strict inclusion and 
exclusion criteria [23]. 
Foot orthotics, available in both customised and off-the-shelf forms, might offer a potential 
solution to these challenges [24,25]. With direct-to-consumer marketing, these orthotic devices 
are often presented as remedies capable of alleviating an array of both foot-related issues as 
well as pain and discomfort [26,27]. Yet, the literature on their benefits is somewhat equivocal. 
Many studies have an observational or non-randomised design [28], while other studies 
compare custom orthotics with sham or generic insoles [29–31], which may carry their own 
therapeutic properties, potentially diluting the observed benefits of the customised versions. 
To date, however, the most compelling evidence of orthotic interventions includes the effect 
on specific diagnoses such as plantar fasciitis [32], and Achilles tendinopathy with moderate-
to-low certainty of short-term pain reductions [33]. These conditions, while common among 
runners [10], are often alleviated using a comprehensive treatment approach, in which the 
effect of the orthotics is often assessed as an adjunct part of the treatment including and patient 
education in combination with other interventions like physical therapy and rehab exercises 
[33,34], and corticosteroid injections[34]. This adjunct approach might cloud the isolated 
effects of the insole, and it remains uncertain whether an insole alone without patient education 
will prove effective in a pragmatic setting, as indeed the prescription of foot orthotics is 
normally associated with some degree of podiatric patient education [34]. 
Considering the complexities in the existing literature, there is a pressing need for a simple 
pragmatic trial designed to assess the immediate and prospective long-term effectiveness of 
customised 3D-printed insoles among the general population of recreational runners. This 
includes individuals with or without pain and with or without specific foot-related conditions 
or definitive diagnoses like plantar fasciitis. By employing intention-to-treat principles in the 

 
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primary analysis, this trial ensures a realistic representation of the insoles' real-world 
effectiveness in a natural setting, invaluable for both healthcare providers and runners. Our 
subsequent secondary analyses will then delve deeper, focusing on responses from those with 
significant baseline pain and specific diagnoses, offering a granular understanding of the 
intervention's effect across different subgroups within the recreational running community. 
Objectives 
Primary research question 
Based on the description provided and existing evidence, we posed the following research 
question: Is the use of Zoles customised 3D-printed insoles, for a duration of 8 weeks, superior 
to a "do-as-usual" control strategy in improving running-related pain among frequent 
recreational runners participating in regular parkrun activities? 
This research question was designed using the PICOT model with the following specifications 
for each element [35]: 
Population: Frequent recreational runners participating in regular parkrun activities. 
Intervention: Zoles customised 3D-printed TPU insoles for ~8 weeks. 
Control: "Do-as-usual" control group. 
Outcome: Improvement in running-related pain. 
Time frame: 10 weeks after baseline (~8 weeks after receiving allocated intervention). 
Primary objective 
The primary objective is to determine the effectiveness of the Zoles customised 3D-printed 
insoles on the change in running-related pain 10 weeks after baseline in frequent recreational 
runners participating in regular parkrun activities. 
Primary research hypothesis 

 
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Our hypothesis is that the Zoles customised 3D-printed insoles, will lead to a significant 
reduction in running-related pain 10 weeks after baseline (~8 weeks after received allocated 
intervention) compared to a "do-as-usual" control strategy among frequent recreational runners 
participating in regular parkrun activities. 
Secondary objectives 
1. To assess the effect of Zoles customised 3D-printed insoles on secondary outcomes 
like: 
a. Global Rating of Change (GRoC) in overall daily pain and discomfort [36]. 
b. Running-related foot/footwear comfort [37]. 
c. 5-k (parkrun) completion time. 
d. Running-related injury incidence rate. 
e. Time-loss from running. 
f. Running exposure in terms of miles and time. 
g. Adherence to the intervention during daily- and running activities. 
h. Adverse events from using the Zoles insoles. 
2. To explore if the control group benefits similarly to receiving customised 3D-printed 
insoles when provided after the initial 10-week primary trial phase. 
3. To understand the long-term effects and durability of the benefits of the Zoles 
customised 3D-printed insoles, assessed one year after the intervention. 
4. To investigate the immediate therapeutic effect of Zoles insoles specifically for 
participants with clinically relevant baseline pain levels (11-NRS ≥ 3) [38]. 
5. To assess pre-trial expectations and post-trial experiences regarding the therapeutic 
effects of the Zoles insoles and understand their influence on the efficacy of the 
intervention within the specific subgroup of participants with high baseline pain levels. 

 
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Methods 
Trial design 
The ZOLES trial is a pragmatic, outcome assessor blinded, randomised, controlled, superiority 
trial, with a two-group parallel design, and a 1:1 allocation ratio. Frequent recreational runners 
will undergo foot scanning and thereafter be randomised to either receive a customised 3D-
printed insole (Zoles ApS, Espergærde, DK-3060, Denmark), or to be in a “do-as-usual” 
control group. The pragmatic design and pre-planned secondary analyses are heavily inspired 
by the SExSI trial [39]. 
The trial protocol is based on the "PREPARE Trial guide" [35] and adheres to the "SPIRIT 
2013 explanation and elaboration: guidance for protocols of clinical trials" [40] and SPIRIT 
checklist (Appendix A). The trial report will follow the “REPORT guide” [41], and thus adhere 
to the CONSORT guidelines for reporting parallel group randomised trials [42], using the 
CONSORT extension for pragmatic trials [43], as well as the updated CONSORT-Outcomes 
2022 extension [44]. The TIDieR template (Appendix B) is used to describe the intervention 
to aid future replication [45]. 
The study was approved by the St Mary’s University Ethics Sub-Committee on 4 August 2023, 
and the trial was pre-registered at ClinicalTrials.gov on 4 September 2023 (ID: NCT06034210) 
[46], before the first participant was enrolled on September 16, 2023.  
Study setting  
Participant screening and enrolment for this study is undertaken from Faculty of Sport, 
Technology and Health Sciences at St Mary’s University (Twickenham, London, United 
Kingdom), with recruitment to the trial being carried out at local parkrun communities, 
primarily from Bushy Park (Richmond upon Thames, London, United Kingdom).  
 
 

 
9 
 
Eligibility criteria 
Inclusion criteria 
a) Participant is ≥ 35 years old at commencement of trial. 
b) Participant can read, speak, and understand English. 
c) Participant can receive e-mails and complete online questionnaires. 
d) Participant is a frequent runner who participate in regular parkrun activities. 
e) Participant is capable of running at commencement of trial. 
Exclusion criteria 
a) Individuals with severe foot deformities will be excluded during the foot scanning 
process if the level of customization needed exceeds what is possible via the Zola 
software. 
b) 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. Evaluated via the Physical Activity Readiness Questionnaire Plus (PAR-Q+) at 
inclusion. 
Interventions 
By virtue of being a pragmatic trial, all participants will be allowed to use or keep using any 
treatment or concomitant care, regardless of their group allocation. Pre-existing use of insoles 
in the intervention group, should naturally be replaced by this study’s intervention. 
Experimental: ZOLES Customised 3D-printed insoles 
Participants allocated to the intervention group will receive customised 3D-printed insoles 
(Zoles ApS, Espergærde, DK-3060, Denmark) to mitigate running-related pain and discomfort 

 
10 
 
(Figure 1). Being a pragmatic trial, all participants are permitted to continue or initiate any 
usual care of their choice.  
Based on measurements from a 3D scanning procedure (Figure 2), and factoring in individual 
data such as age, weight, and activity preferences, custom insoles are designed using the ZOLA 
software. The insoles are then 3D-printed by Zoles ApS in Espergærde (Denmark), using 
BCN3D printers (Barcelona, Spain) and a TPU (Thermoplastic Polyurethane) filament material 
from Recreus (Alicante, Spain). The printed insoles are tailored for optimal support, 
performance, and comfort, with varying densities for areas like the arch and heel. They are 
finished with an OnSteam® microfiber cover for added durability and comfort. The insoles are 
intended for regular insertion into participants' shoes to align with their unique biomechanical 
needs. (Information translated and adapted from [47]). The participants are recommended to 
gradually wear the insoles in over a three-week period (Appendix D) but are otherwise 
encouraged to use the insoles within all their different shoes, and to wear these during all 
activities of daily living and during their running activities. Adherence to the intervention is 
not controlled but simply collected over the duration of the trial. 
A thorough description of the intervention following the TIDieR guidelines [45], including 
reasons for potential needs for modifications of the insoles is included (Appendix B). 
No Intervention: “Do-as-usual” control group 
Participants allocated to the control group are a "do-as-usual" comparator. This implies, that 
the participants may treat and prevent running-related pain and discomfort in any way they 
wish, except using the Zoles 3D-printed insoles. 
Outcomes 
Primary outcome 

 
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The primary outcome will be the change in running-related pain 10 weeks after baseline. Pain, 
although subjective, is a crucial determinant of runners' quality of life, performance, and 
continued participation in the activity [13]. For this trial, an 11-NRS pain scale will be utilized, 
ranging from 0 to 10 (0 = No pain at all, 10 = Worst pain imaginable) [48]. 
Baseline values for the primary outcome will be collected using online e-mail-distributed 
surveys via REDCap (Vanderbilt University, Nashville, TN, USA). Running-related pain data 
will be further collected at weekly intervals, with the focal analysis being between-group 
changes from baseline to the 10-week mark. The main outcome will be reported as the 
difference in mean change in running-related pain between the group using Zoles customised 
3D-printed insoles and the "do-as-usual" control group, adjusting for values reported at 
baseline [49]. 
Secondary outcomes 
The secondary outcomes include: 
• 
Global Rating of Change (GRoC) in overall daily pain and discomfort: Participants 
will be asked to self-assess their perceived change in overall daily pain and discomfort 
relative to their state at the start of the study. They will use a 7-point scale, from -3 
("much worse") to 3 ("much better"), as indicated in the study by Bobos et al. [36] This 
outcome will be measured weekly until the 10-week mark, and again at the 18-week 
mark. 
• 
Running-related foot/footwear comfort: The change in comfort from the start to the 
10-week mark, relating specifically to running and footwear, will be captured using a 
numeric rating scale ranging from 0 (Extremely uncomfortable) to 10 (Extremely 
comfortable) based on the parameters defined by Menz & Bonnano [37]. This outcome 
will be measured at baseline with weekly follow-up measurements until the 10-week 
mark, and again at the 18-week mark. 

 
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• 
5k-completion time: The time taken by participants to complete their weekly 5 km 
parkrun will be recorded weekly, providing insights into any performance changes over 
the trial period. 
• 
Running-related injuries: The incidence rate of injuries related to running will be 
monitored and reported as the number of injuries for every 1000 hours of running 
exposure over the 10-week duration. 
• 
Time-loss: The total number of days participants miss out from running due to pain, 
discomfort, or injury will be tracked weekly for 10 weeks, and again at the 18-week 
mark. 
• 
Weekly Mileage: The distance participants run every week will be recorded during the 
10-week trial period, and again at the 18-week mark. 
• 
Weekly running exposure: The total time participants spend running every week will 
be obtained in hours and minutes for the 10-week trial period, and again at the 18-week 
mark. 
• 
Adherence to intervention, ADL%: This outcome tracks how frequently participants 
use the Zoles insoles for everyday activities such as sitting, standing, walking, and 
driving over the 10 weeks, and tracked again at the 18-week mark, and at the 52-week 
post-market surveillance. 
• 
Adherence to intervention, RUN%: The percentage of time participants wear the 
Zoles insoles specifically during running will be monitored over the 10 weeks, and 
again at the 18-week mark, and at the 52-week post-market surveillance. 
• 
Adverse events from using Zoles insoles: All adverse events associated with the usage 
of Zoles will be reported based on their type and number. Throughout the trial, 
participants will be encouraged weekly to report any adverse events through the trial 

 
13 
 
hotline. Participants will be asked again at the 52-week-post-market-surveillance to 
capture any long-term events. 
 
 

 
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Other Outcomes 
The other outcomes of interest for the pre-planned secondary subgroup analyses include: 
• 
Participants achieving MCID reduction in pain: This measure looks at the 
percentage of participants who manage to achieve a clinically meaningful reduction in 
running-related pain, defined as a reduction equal to or larger than the MCID (NRS ≥ 
2) as described by Salaffi et al. [48]over the 10 weeks. 
• 
Time until MCID reduction in pain: This outcome gauges the time in weeks it takes 
for participants with clinically significant pre-existing pain (NRS ≥ 3 as defined by 
Rathleff et al. [38]) to achieve the clinically meaningful reduction in running-related 
pain (MCID) during the 10-week trial period. 
• 
Change among participants with high baseline pain: For participants who start the 
trial with clinically significant pain (NRS ≥ 3) [38], their specific change in pain over 
the 10 weeks will be captured using a numeric rating scale from 0 (No pain at all) to 10 
(Worst pain imaginable) [48]. 
• 
Pre-trial intervention expectations: Before the trial begins, participants will indicate 
their expectations regarding the therapeutic effect of the Zoles insoles on running-
related pain, 5-k completion time, and footwear comfort using a 5-point Likert scale. 
• 
Post-trial intervention experiences: After the trial, participants will be asked about 
their experiences with the Zoles intervention, indicating whether it met, exceeded, or 
did not meet their initial expectations via a 5-point Likert scale. 
• 
Post-market surveillance: One-year post-trial, all participants (from both control and 
intervention groups) will be surveyed to assess the long-term effects and benefits of the 
Zoles insoles. This survey will include the primary outcome and all key secondary 
outcomes, allowing for a comprehensive evaluation over a longer period. 
 
 

 
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Participant timeline 
Participants are first recruited at the finish line of local parkruns on Saturday mornings during 
the enrolment phase (Timepoint -1). Those interested are invited to invited to the Biomechanics 
Laboratory of the Faculty of Sport, Technology, and Health Sciences at St Mary’s University 
in Twickenham, London, UK, or to an in-field assessment (for the North London area). Here, 
they receive detailed oral and written information about the study, and if willing to proceed, 
sign the written informed consent form. On this day of enrolment, participants also have their 
feet scanned, initiating the process that customises and orders their insoles on the spot. 
The allocation phase (Timepoint 0) commences post-enrolment, where participants are sent a 
baseline questionnaire. The information gathered from this questionnaire is used in the 
balanced block randomisation procedure. Upon completion of the baseline questionnaire, 
participants are set up to receive weekly follow-up surveys during the primary study period 
(Weeks 1-10). During this period, there is weekly follow-up on primary and secondary 
outcomes, delivery of allocated intervention group insoles projected before week 3, and weekly 
monitoring of adherence and adverse effects. In a case where a pair of insoles do not fit inside 
a participant’s footwear, a fast-track adjustment, production, and shipment procedure takes 
place, ensuring a minimal delay of insole delivery of approximately one week. 
In the control group step allocation period (Weeks 10-18), control group participants receive 
their customised insoles and all participants are sent a single event follow-up questionnaire at 
week 18. This questionnaire covers primary and secondary outcomes, as well as adherence and 
adverse effects. 
Finally, post-market surveillance occurs at Timepoint Week 52, a year after the study's 
commencement. All participants receive a follow-up questionnaire assessing their post-trial 
experiences with the insoles, any adverse effects experienced during the year, and the long-
term effects of the Zoles insoles (Figure 3). 

 
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Sample size 
The sample size estimation is based on the primary outcome, running-related pain. Lopes et al. 
[9] reported a median pain level of 3 (IQR: 2-5) among 1049 recreational runners. We expect 
similar pain levels at baseline which, if normally distributed, should result in a mean pain of 3 
and a standard deviation of 2.22 (SD≈IQR/1.35). We forecast a 40% reduction in running-
related pain in the intervention group over the course of the trial (from baseline to follow-up). 
Using the formula n = (Zα/2+Ζβ)2 * 2σ²/d², where d is the expected difference between groups, 
to detect a 40% reduction in pain (1.2 units) with 80% power at a 5% significance level, we 
initially require 70 participants per group [50]. Factoring in an anticipated 15% dropout, this 
number increases to 82 participants per group. To accommodate the pre-planned secondary 
subgroup analyses in the future, we further inflate the number by approximately 20%, leading 
to a total of 100 participants in each group. Hence, this study aims to recruit a cumulative 
sample size of 200 participants. 
Recruitment 
Participants are primarily targeted and approached within the local London parkrun 
communities. Following their routine Saturday 5-km run, a strategic engagement occurs where 
they will be approached by study representatives. The parkrun offers a natural setting to 
converse with potential participants who are already involved in regular running activities. 
During this engagement, participants are presented with an oral briefing about the study, its 
objectives, and the potential benefits of their participation. This method not only taps into a 
pool of runners but also allows for immediate interaction, answering any initial queries they 
might have. Interested runners, eager to contribute or benefit from the study, are subsequently 
invited to the Biomechanics Laboratory of the Faculty of Sport, Technology, and Health 
Sciences at St Mary’s University in Twickenham, London, UK. Here, they are introduced to 

 
17 
 
the broader scope of the study, the commitment expected from them, and the potential 
implications of the research, and ultimately a formal enrolment into the study. 
Allocation 
Upon completion of the baseline questionnaires, participants will be equally distributed (1:1 
ratio) to the two comparison groups (intervention group and “do-as-usual” control group) using 
a balanced block randomisation method.  
Specifically, the block randomisation will be stratified by sex and the specific parkrun location 
from which participants were recruited. This stratification ensures that each comparison group 
will have a representative mix of participants based on these two key variables, pre-
hypothesised as potential confounders, allowing for a more controlled comparison of 
outcomes, and to improve external validity and generalisability of the results [51]. 
The process of generating the allocation sequence will be undertaken by an external who is not 
involved in any aspect of the trial to improve the integrity and credibility of the allocation 
process, as recommended [52]. The dataset provided for randomisation will only contain 
participant number, local parkrun location, and sex. The data will be initially separated by sex, 
and within each gender group, a stratification variable will be created based on local parkrun 
location. Block randomisation, with a block size of 4, will be conducted separately for males 
and females within each stratum (location) using a custom script developed in R. This approach 
ensures an equal or near-equal distribution of males and females within each treatment group 
across all locations. The randomisation process within each stratum will be automated through 
the script, and the resulting group assignments will be merged back into the original dataset. 
The R script used for the randomisation will be available as supplementary material to the 
primary trial report. Once the allocation sequence is generated, participants will be informed 
of their respective group assignments, either the intervention group (receiving the ZOLES 
insoles) or the control group ("do-as-usual"). 

 
18 
 
Blinding 
Given the pragmatic nature of this trial, participants are not blinded to their group allocation. 
The absence of a sham insole for distribution means that participants will be aware of whether 
they are in the intervention group (receiving the ZOLES insoles) or the control group ("do-as-
usual"). Despite this, the allocation process remains concealed, ensuring that neither 
participants nor researchers are aware of to the allocation sequence until the appropriate 
intervention shall be administered. This measure is in place to prevent any potential biases that 
might arise from foreknowledge of group assignments [53,54]. To further the study’s integrity, 
we will use an external outcome assessor that is blinded to group assignments [55]. 
Procedures and data collection 
During the enrolment visit to either the Biomechanics Laboratory of the Faculty of Sport, 
Technology and Health Sciences at St Mary’s University (Twickenham, London, United 
Kingdom), consenting participants will undergo a quick foot scanning procedure (≤10 seconds 
per foot) while standing in talocrural neutral position with weight evenly distributed on both 
legs. Scanning is conducted using the DOMEscan/IBV (Instituto de Biomecanica de Valencia, 
46022, Valencia, Spain) (Figure 2) that is controlled via the ZOLA software (Zoles ApS, 
Espergærde, DK-3060, Denmark), allowing for real-time design and ordering of the 
customised insoles tailored to each participant’s unique foot structure. The ZOLA software 
also records and collects the scanning data and brief participant information in the form of age, 
weight, sex, shoe size, shoe brand and model, and type of activity (running) for which the insole 
should be designed. Specific medical diagnoses related to the lower extremities, such as plantar 
fasciitis, shin splints, etc., are also collected at this stage if known by the participants. The same 
procedure will be followed for the in-field enrolments in North London, where the DOMEscan 

 
19 
 
foot scanner and laptop running the ZOLA software will be powered using a portable power 
station (606Wh MPPT Solar Generator, ALLPOWERS, Guangzhou City, China). 
Following the foot scanning, participants are sent a baseline questionnaire via email, enabling 
them to provide responses from the comfort of their homes and ensuring an unbiased, natural 
representation of their baseline pain and comfort levels. This phase ensures that participants’ 
responses are free from the potential influence of the on-site researchers. 
The trial will include prospective data collection using e-mail-distributed surveys via REDCap 
(Vanderbilt University, Nashville, TN, USA). Participants receive these surveys weekly for the 
initial 10 weeks, facilitating the collection of real-time data on their experience, pain levels, 
and the impact of the customised insoles for those in the intervention group. At the conclusion 
of this primary trial period (week 10), participants in the control group are provided with their 
customized insoles, marking the commencement of an additional 8-week observation period to 
compare intervention response between both groups (week 18). The final follow-up occurs at 
the 52-week mark, again via REDCap to provide insights on their long-term experiences, 
adverse effects, and the sustained impact of the Zoles insoles on their running-related pain and 
comfort. 
Reminders will automatically be sent to participants at 24 hours and 48 hours after the original 
time of a follow-up questionnaire to participants failing to respond. Investigators will contact 
participants via telephone and SMS after another 24 hours if still not responding after receiving 
reminders to reduce the amount of missing data. 
Data management 
Every participant is assigned a unique identification number, ensuring their anonymity 
throughout the study in compliance with the General Data Protection Regulations (GDPR) 
under the Data Protection Act 2018. 

 
20 
 
Data collection, both at baseline and throughout the prospective stages, is facilitated via 
REDCap, a secure and robust online platform renowned for its data management capabilities 
[56]. This process is overseen from Department of Clinical Medicine at Aalborg University 
(DK-9220, Aalborg Øst, Denmark) by a dedicated data handler (CD), who remains blinded to 
group allocation. CD and FGL constitute the Data Monitoring Committee. A list of responding 
and non-responding participants is generated weekly, wherefrom a list of non-responding 
participants to contact is generated.  
The Study Director (FGL) will maintain a secured key to the participants’ identities, stored on 
a two-factor secured personal drive, ensuring the capability to identify and withdraw individual 
data if necessary. 
All data is safeguarded within GDPR compliant two-factor and password-protected systems at 
St. Mary’s University server, and on the REDCap online system. These measures ensure that 
the data remains inaccessible to unauthorized personnel, preserving confidentiality. 
In adherence to transparency and scientific scrutiny, a fully anonymised dataset at the 
participant level, accompanied by the corresponding statistical code, will be made available to 
the public, contingent upon the requirements of the journal publishing the study’s findings. 
This disclosure ensures the replicability and verification of the research while upholding the 
anonymity and privacy of all participants. 
The published results will omit any information that could potentially be used to identify 
individual participants.  
Statistical methods 
The primary outcome; change in running-related pain from baseline to follow-up, will be 
calculated using negative binomial regression. Figure 4 illustrates a hypothetical change in pain 
over the course of the trial, including the expected catch-up by the control group at week 18. It 
is important to note, however, that the between-groups analysis for difference will adjust for 

 
21 
 
values reported at baseline [49,57]. 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 
analysed based on initial randomisation. 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.  
Possible effect modifiers include time with allocated intervention due to possible logistics 
issues in handing over the insoles to the intervention group, as well as any last-minute needs 
for sizing adjustments if a pair of insoles do not fit inside a participant’s footwear. Any new 
injury sustained during the trial period is another potential effect modifier. No potential 
external effect modifiers will be factored in the intention-to-treat analyses. 
Statistical methods – secondary subgroup analysis and post-market surveillance 
The subsequent secondary analysis publication will hold the label "secondary and long-term 
follow-up analysis from a pragmatic randomised 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) [38]. 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.  

 
22 
 
The between-groups difference among participants with clinically baseline pain levels will be 
analysed similarly to the primary outcome. Subsequent regression models will, however, also 
be structured to comprehend the potential influence of pre-intervention expectations and post-
intervention experiences, as well as adherence to the intervention on the Zoles insoles' 
effectiveness within this subgroup. This involves incorporating these factors as covariates in 
the model. 
Statistical methods – analysis population and missing data 
For the primary and secondary outcomes of this trial, an intention-to-treat (ITT) analysis 
approach will be employed [58]. This method ensures the inclusion of all randomised 
participants in the analysis, irrespective of their adherence to the intervention. Participants will 
be analysed based on their initial randomisation. As such, any deviations from the intervention 
or missing follow-ups will not impact the participant's initial group classification in the 
analysis, as recommended by the CONSORT group [42,44]. 
To accommodate this approach, missing outcome data will be imputed using multiple 
imputations by chained equations [59].  The imputation procedure will include the following 
variables pre-hypothesised to potentially predict missing information: a) preceding scores 
relevant to the outcome in question, b) age of the participant, c) sex of the participant, d) group 
allocation, and d) location of recruitment (specific parkrun location). 
Harms 
Adverse events, within the context of this study, are defined as any unintended symptoms, 
injuries, or illnesses that participants experience while being allocated to the intervention, 
regardless of attribution. These could manifest anytime following the introduction of the 3D-
printed insoles and until the one-year follow-up.  

 
23 
 
The recording of these events is pivotal and will be initiated by the participants through 
spontaneous reporting. Every interaction with participants, be it during prospective follow-ups 
or the post-market surveillance stage, will underscore the importance of reporting any and all 
adverse effects. Participants will be systematically reminded of this imperative, ensuring a 
thorough and comprehensive documentation of potential adverse events associated with the 
use of the insoles. Regular auditing planned throughout the study in the form of pre-scheduled 
meetings between the principal investigator (SI), study director (FGL) and local study chair 
(RM). 
Serious adverse events are categorised according to the criteria established by the United States 
Food and Drug Administration [60]. The primary investigator undertakes the responsibility of 
evaluating these events, assessing their potential association with the intervention. Every 
incident is examined to discern if there is a reasonable possibility that the insoles contributed 
to the adverse event. In the unfortunate occurrence of serious unexpected adverse events, these 
will be immediately reported to the St Mary's University Ethics Sub-Committee within 7 days 
of the event’s occurrence. 
Ethics and dissemination 
This study is anchored in stringent ethical guidelines, ensuring alignment with the World 
Medical Association (WMA) Declaration of Helsinki and adherence to the General Data 
Protection Regulations (GDPR) under the Data Protection Act 2018. Ethical approval was 
granted from St Mary’s University Ethics Sub-Committee on August 4, 2023. Consistent with 
the recommendations of the CONSORT group [42] and the International Committee of 
Medical Journal Editors (ICMJE) [61], the study was pre-registered on ClinicalTrials.gov on 
September 4, 2023. To maintain transparency and ethical integrity, any modifications to the 
protocol will be duly updated on ClinicalTrials.gov, communicated to the University Ethics 

 
24 
 
Sub-Committee, and disclosed in the published primary trial paper. Upon the study’s 
completion, a formal notification will be submitted to the ethics committee within 30 days, 
confirming the end of the trial. 
Dissemination policy 
All study results, regardless of their nature, will be published in international scientific journals, 
assured by an unrestricted publication agreement with Zoles ApS, the insole manufacturer. 
Results will also be shared at both national and international conferences to ensure a broad 
dissemination. We are committed to adhering to the Vancouver conventions by the 
International Committee of Medical Journal Editors (ICMJE) for ethical authorship. The 
primary trial report will clearly outline, and reference all collected outcomes, directing readers 
to the comprehensive dissemination plan for details on unreported data or analyses. Working 
titles for all journal publications to be associated with this study are listed below: 
1. The effectiveness of customised 3D-printed insoles on perceived pain, comfort, and 
completion time among frequent Park Runners: Study protocol for a pragmatic 
randomised controlled trial (The ZOLES RCT) 
2. The effectiveness of customised 3D-printed insoles on perceived pain, comfort, and 
completion time among frequent Park Runners: A pragmatic randomised controlled 
trial (The ZOLES RCT) 
3. The effect of customised 3D-printed insoles among frequent Park Runners with high 
clinically relevant running-related pain: pre-planned secondary and long-term follow-
up analysis from a pragmatic randomised controlled trial (The ZOLES RCT) 
 
 

 
25 
 
Discussion 
This study is designed to investigate the effectiveness of customised 3D printed insoles in 
alleviating pain, enhancing comfort, and improving completion time amongst recreational 
parkrun participants. The study is meticulously crafted, aligning with the FINER-criteria, 
ensuring it is Feasible, Interesting, Novel, Ethical, and Relevant [35].  
Pain and niggles are common issues among active runners, and not only impede performance, 
but also potentially lead to a reduction in physical activity and an associated increase in 
premature mortality risk [6,13,15]. 
The potential of 3D customised insoles to mitigate these common issues stems from a grounded 
hypothesis supported by preliminary evidence [21,25,29], suggesting their effectiveness in pain 
reduction. The simplicity and accessibility of this intervention underscore its potential 
widespread applicability and adoption amongst the running community. If proven effective, 
these insoles could serve as a convenient and practical solution, addressing pain while 
enhancing the overall running experience. 
The pragmatic approach of this trial is anchored in a design that maximises the utility and 
applicability of the findings. Every aspect, from the real-world setting to a diverse participant 
base, is tailored to ensure that the results are not only scientifically rigorous but also practically 
insightful. In a realm where pain is often a limiting factor, interventions that are both effective 
and easily integrable are pivotal [62].  
Strengths and limitations 
A major limitation of this study is the absence of blinding for the intervention, which could 
potentially introduce bias in the self-reported outcomes, particularly as the primary outcome, 
pain, is inherently subjective. This subjectivity could amplify the Hawthorne effect, leading to 
potential biases that are not directly attributable to the intervention itself [63]. The 
implementation of a sham insole or an off-the-shelf comparator could have mitigated this 

 
26 
 
limitation by providing a control for the placebo effect and the subjective improvement due to 
participants’ awareness of the treatment. However, this study is designed with a pragmatic 
perspective that aligns with real-life scenarios where no sham insole would be offered to a 
potential customer or patient. 
We acknowledge the potential impact of a ‘pleasing effect’ but chose not to blind the 
hypothesis for the participants because the primary motivation for seeking orthotics in real-
world contexts is often pain mitigation. We aim for the study results to be as applicable as 
possible to these real-world scenarios, and thus, accepting this limitation was a considered 
decision to enhance the external validity and practical applicability of our findings. The study 
is designed to evaluate the effectiveness of the insoles in conditions that closely mimic the 
everyday experiences and choices of runners seeking solutions for pain relief. 
Despite these challenges, the study’s structure and methodology have been meticulously 
crafted to yield insights that are both scientifically rigorous and practically insightful, balancing 
between the ideal conditions for experimental control and the complexities of real-world 
application. Conversely, this study boasts several strengths that bolster its reliability and 
validity. The use of blinded group allocation sequence, external outcome assessors who are 
blinded to the group assignments, and an external data manager also blinded to group allocation 
ensures objectivity in data collection and analysis, minimizing bias. Furthermore, the recording 
of all outcomes in participants’ natural environments, including baseline data, amplifies the 
real-world applicability of the findings. Participants are thus not influenced by the study 
personnel, ensuring the outcomes reflect the real-life effect of the intervention, enhancing the 
study's external validity. Additionally, the employment of a mobile scanning unit allows us to 
recruit participants from more distant parkrun locations, thus allowing for enrolment of 
participants who might not have the means to travel across London to partake in this study. 

 
27 
 
The intention to treat analysis in the primary study report ensures all participants are included 
in the final analysis, maintaining the randomisation benefits and offering a conservative 
estimate of the intervention's effectiveness. The step-wedge design addition enhances the 
study’s robustness, allowing immediate verification of effectiveness by comparing the control 
group’s response post-primary trial period to the intervention. The inclusion of a 52-week post-
market surveillance further elevates the study’s comprehensiveness, offering insights into the 
long-term effects and usability of the insoles.  
Transparency is maintained through pre-registration of the study and the detailed description 
of the intervention using the TIDieR checklist [45], ensuring replicability and openness in 
reporting. The publication of this study protocol underscores the commitment to transparent 
and ethical research practices, contributing to the broader scientific discourse and public 
scrutiny. 
Despite the limitations, we believe the robust design of this study sets a significant precedent 
for evaluating biomechanical interventions in real-world settings. We believe that this study 
design can form a framework for future research, ensuring that studies are as realistic as they 
are rigorous, by offering a comprehensive understanding of biomechanical interventions within 
their intended settings. 
Trial status 
Protocol version 1, September 27, 2023. Recruitment for this study started on September 16, 
2023, and concluded on October 2, 2023.  
 
 
 

 
28 
 
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Declarations 
Ethics approval and consent to participate 
Ethical approval was granted from St Mary’s University Ethics Sub-Committee on August 4, 
2023 (ID: SMU_ETHICS_2022-23_325). All participants must sign an informed consent form 
prior to participation. 
Consent for publication 
 
Not applicable 
Availability of data and materials 
Upon the release of the trial findings, a completely anonymised dataset at the participant level, 
along with the relevant statistical code, will be disclosed to the public if mandated by the 
publishing scientific journal. If the journal does not necessitate the full dataset's release, such 
an anonymised dataset can be obtained from the study director, FGL, author upon reasonable 
request. 
Declaration of interests 
The authors declare that they have no competing interests. 
Zoles ApS and affiliates have no role in the study, and are restricted from any involvement in 
the design of the study, execution, analyses, interpretation of data, writing of the manuscript, 
or in the decision to submit for publication. The Study Director has full authority of the trial 
administration and decision for publication. 
Funding 
This is an investigator-initiated trial. The funding for this study is provided by St Mary's 
University Faculty of Sport, Technology and Health Sciences (STHS) QR Funds. Zoles ApS 
has graciously contributed the customised 3D printed insoles for all study participants, valued 
at approximately £23,000. Zoles ApS is also responsible for supplying the 3D scanners 

 
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(DOMEscan/IBV, Instituto de Biomecanica de Valencia, 46022, Valencia, Spain) that are used 
to scan the participants' feet, training and support of St Mary's staff members. 
Authors’ contributions 
FGL is the study director, he conceived the study, led the proposal and protocol development, 
primary supervisor overseeing the overall conduct of the study. SI is the principal investigator, 
leading the core investigative efforts. RM and CD shared the role of study chair; RM also acted 
as co-supervisor, while CD managed data collection. KT, also a study chair, contributed senior 
clinical trial expertise and senior supervision. All authors participated in designing the study, 
refining the protocol, and approved the final study registration and manuscript. 
Acknowledgements 
We express our thanks to the local parkrun organisers for their support and collaboration. Their 
assistance in participant recruitment will be crucial to this study's initiation and progress. 

 
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Figures 
Figure 1: Zoles 3D-printed insole exemplar. Picture provided and used with permission from 
Zoles ApS.  
Figure 2: Example of foot scanning process of a right foot using the DOMEscan/IBV 3D 
scanner. 
Figure 3: Participant timeline in the SPIRIT (Standard protocol items: Recommendations for 
interventional trials) diagram 
Figure 4: Visualisation of change in pain score in the intervention (blue) and control group 
(red), respectively (Example, not based on data).  
 
 
 

 
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Figure 1
 

 
41 
 
Figure 2 
 
 
 

 
42 
 
Figure 3 
 

 
43 
 
Figure 4 
 

 
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Appendices 
A 
SPIRIT checklist 
 
B 
TIDieR intervention Checklist 
 
C 
Intervention leaflet 1 
 
D 
Intervention leaflet 2 
 
E 
Participant consent materials 
 
F 
Baseline questionnaire 
 
G 
Weekly follow-up questionnaire 
 
H 
WHO Trial Registration Data Set (Version 1.3.1)