RESEARCH ARTICLE
Shoe feature recommendations for different
running levels: A Delphi study
Eric C. HonertID1☯*, Maurice Mohr1,2☯, Wing-Kai LamID3,4,5☯, Sandro Nigg1☯
1 Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada,
2 Institue of Sport Science, University of Innsbruck, Innsbruck, Austria, 3 Guangdong Provincial Engineering
Technology Research Center for Sports Assistive Devices, Guangzhou Sport University, Guangzhou, China,
4 Department of Kinesiology, Shenyang Sport University, Shenyang, China, 5 Li Ning Sports Science
Research Center, Li Ning (China) Sports Goods company, Beijing, China
☯ These authors contributed equally to this work.
* eric.honert@ucalgary.ca
Abstract
Providing runners with footwear that match their functional needs has the potential to
improve footwear comfort, enhance running performance and reduce the risk of overuse
injuries. It is currently not known how footwear experts make decisions about different shoe
features and their properties for runners of different levels. We performed a Delphi study in
order to understand: 1) definitions of different runner levels, 2) which footwear features are
considered important and 3) how these features should be prescribed for runners of different
levels. Experienced academics, journalists, coaches, bloggers and physicians that examine
the effects of footwear on running were recruited to participate in three rounds of a Delphi
study. Three runner level definitions were refined throughout this study based on expert
feedback. Experts were also provided a list of 20 different footwear features. They were
asked which features were important and what the properties of those features should be.
Twenty-four experts, most with 10+ years of experience, completed all three rounds of this
study. These experts came to a consensus for the characteristics of three different running
levels. They indicated that 12 of the 20 footwear features initially proposed were important
for footwear design. Of these 12 features, experts came to a consensus on how to apply five
footwear feature properties for all three different running levels. These features were: upper
breathability, forefoot bending stiffness, heel-to-toe drop, torsional bending stiffness and
crash pad. Interestingly, the experts were not able to come to a consensus on one of the
most researched footwear features, rearfoot midsole hardness. These recommendations
can provide a starting point for further biomechanical studies, especially for features that are
considered as important, but have not yet been examined experimentally.
Introduction
Matching running footwear features to the functional needs of the runner has the potential to
improve footwear comfort [1,2], enhance running performance [3,4] and reduce the risk of
overuse injuries [1,5]. The majority of biomechanical studies have examined the effects of
PLOS ONE
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
1 / 17
a1111111111
a1111111111
a1111111111
a1111111111
a1111111111
OPEN ACCESS
Citation: Honert EC, Mohr M, Lam W-K, Nigg S
(2020) Shoe feature recommendations for different
running levels: A Delphi study. PLoS ONE 15(7):
e0236047. https://doi.org/10.1371/journal.
pone.0236047
Editor: Chris Harnish, Mary Baldwin University
Murphy Deming College of Health Sciences,
UNITED STATES
Received: March 12, 2020
Accepted: June 26, 2020
Published: July 16, 2020
Peer Review History: PLOS recognizes the
benefits of transparency in the peer review
process; therefore, we enable the publication of
all of the content of peer review and author
responses alongside final, published articles. The
editorial history of this article is available here:
https://doi.org/10.1371/journal.pone.0236047
Copyright: © 2020 Honert et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
footwear interventions for a general group of runners and/or athletes rather than specific
groups of runners, stratified according to their training status and/or running experience. This
is despite evidence that runners of different levels (e.g. novice, recreational, high caliber) have
clear differences in functional needs and running goals that need to be addressed in the design
of their footwear (e.g. through cushioning or stability features, [6–9]). As a result, there is a
large gap of knowledge on how to match specific footwear features, and their properties, to
runners from different levels. This gap in knowledge limits the potential beneficial effects that
more individualized footwear may have on comfort, performance or injury risk.
Literature has presented a variety of definitions for different running levels. Studies have
suggested standard definitions for different runner levels, which have been derived from sub-
jective questionnaires [6,7]. However, these definitions are often not translated to biomechani-
cal studies examining footwear features for runners. For example, subjective questionnaires
indicate that recreational runners run, on average, between 25 and 35 km/week [7]. Yet, bio-
mechanical studies have recruited “recreationally running” subjects with an average training
distance between 10 km/week [10] and 50 km/week [11]. On the other hand, literature has
consistently described novice runners as having little to no running experience in the past year
(see [9] for a Meta-Analysis of novice runners). Due to the wide range of definitions for run-
ning levels used in literature, there is a need to reach a consensus on an operational definition
for different running levels.
Modern running shoes are complex systems. They incorporate many different features (e.g.
crash-pads, heel counters, flares, midsole hardness) and each of these features can be included,
excluded and/or tuned individually to modify the characteristics of the final running shoe sys-
tem (e.g. cushioning, stability, heel-to-toe transition, energy return). Some of these shoe fea-
tures have been studied more extensively than others [12,13]. A strong research focus on
certain footwear features does not necessarily translate into agreement on how modifying
these features may affect the running mechanics, performance, injury risk or footwear comfort
in runners of different levels. For example, a recent review found inconclusive evidence
regarding the biomechanical effects of different midsole hardness—one of the most studied
footwear features [13]. On the other hand, there has been little scientific attention on footwear
features such as outsole traction or forefoot flares. A lack of scientific attention could indicate
that the prescription of these features to different runner levels is trivial, these features are not
considered important by footwear professionals or little is known on how to prescribe these
features. An understanding of how footwear experts make decisions about different footwear
features and their properties can be obtained through gathering and summarizing opinions of
experts in the field of running biomechanics and footwear using a Delphi study. The Delphi
method has been utilized for gathering and summarizing opinions via survey-based responses
of an expert panel in order to obtain consensus on complex topics. For example, this technique
has been successfully applied to establish the now frequently reported “Minimalist Index” of
running shoes [14]. Such an understanding can target future systematic investigations around
the presumed optimal property of important footwear features.
The purpose of this study was to utilize a Delphi technique to summarize the opinions of
running footwear experts and reach consensus on 1) runner level definitions, 2) which foot-
wear features are important when designing footwear for different running levels, and 3)
matching the specific properties of footwear features to the respective running levels.
Methods
Footwear experts were asked to complete three rounds of a Delphi study, with each successive
round building on the results gathered from the previous round. Three runner level definitions
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
2 / 17
Funding: “Li-Ning provided support in the form of
a salary for WKL, but did not have any additional
role in the study design, data collection and
analysis, decision to publish, or preparation of the
manuscript. The specific role of WKL is articulated
in the ‘author contributions’ section”.
Competing interests: “WKL affiliation with Li-Ning
does not alter our adherence to PLOS ONE policies
on sharing data and materials”.
were refined throughout the three rounds of the Delphi study through expert feedback. Experts
were also provided a list of 20 different footwear features. Through the three rounds of the
study, experts provided opinions on which features were important and what their properties
should be for the three different running levels.
Delphi study
In total, 142 experts from 18 countries were contacted by e-mail to participate in this Delphi
study: 44 academics, 35 journalists, 25 coaches, 24 scientists in the footwear industry, seven
bloggers and seven physicians. The participants for this Delphi study were compiled from:
authors that appeared on multiple papers from a recent literature review [13], podium present-
ers at the 2019 Footwear Biomechanics Symposium, coaches of national and/or college track
and field teams with publicly available e-mail addresses, scientists working in research and
development at the leading running footwear brands, running shoe bloggers and journalists
identified from an online search of popular running blogs and magazines and running and/or
footwear journalists that Professor Benno Nigg has compiled over the years. All potential par-
ticipants were contacted via e-mail to participate in this Delphi study. Participants were
excluded if they had under two years of experience related to running footwear in their respec-
tive fields of expertise. Each participant was provided an implied consent form stating that
returning the survey was their agreement to participate. The protocol was approved by the
University of Calgary’s Conjoint Heath Research Ethics Board (REB19-0240). The footwear
experts completed web-based surveys through QuestionPro (questionpro.com) and could pro-
vide feedback after the completion of each round of this Delphi study. The participants that
completed the first-round survey were invited to participate in the second-round. Similarly,
the participants that completed the second-round survey were invited to participate in the
third round. To prevent bias in the responses and feedback, all participants’ survey responses
were anonymized by the QuestionPro platform. All participants were encouraged to e-mail the
authors upon completion of each respective round of the Delphi study for additional feedback
and/or comments, and to create a list of respondents for successive rounds of the survey.
Running levels
Three different running levels were initially proposed: novice, recreational and high caliber.
The initial characteristics of each running level (Table 1) were defined based on running litera-
ture [6,7,9–11,15–20]. The proposed characteristics provide guidelines for runner classifica-
tion. As such, there were overlaps in the running distance per week between the running levels
in order to accommodate runners that train less and have a better running performance. Feed-
back on the running level definitions was requested from the participants during each round
of the Delphi study. The feedback from rounds one and two was integrated into the running
level definitions and presented to the participants in rounds two and three, respectively. In
each round, the experts rated the running level definitions on a 10-point scale where “1” indi-
cated that the definitions were “Not at all appropriate” and “10” indicated “Most Appropriate”.
Novice runners—Initial definition.
Novice or occasional runners have little running
experience. These runners typically have less than six months of cumulative regular running
training (i.e. at least one day per week) over the previous 12 months [9,15,17]. They run zero
to three times per week with a maximum of about 20 km per week [6,7,10]. Novice runner per-
formance (Table 1) was extrapolated from an average running pace [10]. These runners are
typically not involved in marathons [7]. Surveys have shown that these runners run to improve
general health, manage stress and weight [7]. Novice runners may choose footwear based on
comfort [16], reduce injury risk and improve performance [7].
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
3 / 17
Recreational runners—Initial definition.
The recreational group is the largest running
group [7]. These runners typically have more than six months of cumulative regular running
training (i.e. at least one day per week) over the previous 12 months [10,15]. They run one to
five days per week for a total of 10 to 50 km per week [6,7,10,11,15]. Recreational running per-
formance (Table 1) was extrapolated from running times reported in [21]. Surveys have shown
that these runners run to improve general health, manage stress and be involved with a team
[7]. Recreational runners may choose footwear based on comfort [16], reduce injury risk and
improve performance [7].
High caliber runners—Initial definition.
High caliber runners have significant distance
running experience, train almost daily and regularly compete in regional to international com-
petitions [18]. These runners typically have over three years of regular running experience
[7,20]. They run about three times per week for at least 30 km per week [6,7]. High caliber run-
ning performance (Table 1) inclusion criteria has been reported in several running studies
[18–20]. Surveys have shown that these runners run to improve general health, manage stress
and compete [7]. High caliber runners may choose footwear based on performance, comfort
and reduced injury risk [7,16].
Footwear features
Twenty running footwear features were initially assessed in this Delphi study. These features
were chosen from an initial list of 31 footwear features that were identified based on a prelimi-
nary literature review, market analysis and internal discussion. Two influential studies during
this process were reports from [6] and [14]. This initial list was reduced to 23 features by
removing or joining related features that were reflected in other features or similar in their
function, respectively (e.g. remove midfoot midsole hardness and only retain forefoot and
rearfoot midsole hardness). Pilot testing with four footwear experts (not included in the main
study) indicated that a survey including 23 features required more than an hour to complete
and could potentially lead to a high-drop out rate. Therefore, we limited the number of foot-
wear features to 20, by removing features that pilot participants indicated had low relevance
Table 1. Initial definitions of running levels.
Level 1
Novice
Level 2
Recreational
Level 3
High-caliber
Running experience
Less than six months of regular
running experience
More than six months of regular
running experience
More than three years of regular
running experience
Running habits
0–3 sessions / week
1–5 sessions / week
> 3 sessions / week
5–20 km / week
15–50 km / week
> 30 km / week
Running performance (times are for
male runners)
5km time > 30 min OR
5km time > 20 min OR
5 km time 15–20 min$ OR
10km time > 60 min
10km time > 45 min OR
10 km time 30–45 min$ OR
No marathon racing
Marathon time 3–4.5 h
Marathon time <3h$
Running motivation (ordered according
to importance)
Improve general health
Improve general health
Improve general health
Stress management
Stress management
Stress management
Weight management
Team affiliation
Competition
Priorities for footwear design (from high
to low)
1) Improve comfort
1) Improve comfort
1) Improve performance
2) Reduce injury risk
2) Reduce injury risk
2) Improve comfort
3) Improve performance
3) Improve performance
3) Reduce injury risk
The () indicates regular running experience defined as running at least once per week. The ($) indicates that elite runners with faster race times than high caliber
runners were not considered since they represent a small percentage of the population and may require individual running footwear recommendations.
https://doi.org/10.1371/journal.pone.0236047.t001
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
4 / 17
(e.g. upper overlays or varus alignment). In return, the option was added for experts to suggest
footwear features that should be added to the questionnaire. The final 20 footwear features
assessed in this Delphi study were (see S1 Appendix for description of each feature): crash pad,
forefoot flares, forefoot longitudinal bending stiffness, forefoot midsole hardness, heel counter,
heel flare, heel (stack) height, heel-to-toe drop, insole shape, medial post, midfoot longitudinal
bending stiffness, midsole thickness, outsole traction, rearfoot midsole hardness, rocker (heel),
shoe mass, toe spring (forefoot rocker), torsional bending stiffness, upper material (breathabil-
ity) and upper material (elasticity).
The importance of the footwear features was assessed in the first-round and verified in the
second-round. In the first-round, participants were asked if each footwear feature was impor-
tant when designing footwear for different running levels. The experts could choose between
the following for each footwear feature: (a) is important, (b) is not important or (c) they do not
know if it is important. If over 75% (a similar threshold to [22,23]) of the first-round partici-
pants selected option (a), the footwear feature was defined as important. The important fea-
tures were then presented to the second-round participants. The participants were asked if
they agreed with the list of the features selected as important/non important on a 10-point
scale where “1” indicated that the list of important/non important features was “Not at all
appropriate” and “10” indicated “Most Appropriate”. The list of important features was veri-
fied if over 75% of the second-round participants answered with a seven or higher on the 10
point-scale. The second- and third-rounds of the Delphi study were then limited to the impor-
tant footwear features. In each round, the experts were asked if other footwear features should
be included in the Delphi study. If there were at least five suggestions to add a certain feature,
this new feature was added to the subsequent round. The participants were then asked if this
new feature was important.
Footwear feature properties
The experts were asked to recommend footwear feature properties for the different running
levels in each round of the study from a multiple-choice selection (see S1 Appendix for the lists
of footwear feature properties). Most footwear feature properties were defined based on the
reviewed footwear literature (see S1 Appendix). If there was no related literature (e.g. upper
elasticity), properties were provided based on commercially available shoes. In rounds 2 and 3,
the results from the previous round were presented to the participants. If at least 51% of the
participants agreed on a footwear feature property (a similar threshold to [24]) for a specific
running level (e.g. high breathability for novice runners), the participants would be asked if
they agreed with the consensus the next round. If at least 51% of the participants verified the
consensus, the experts were not asked again to recommend a footwear feature property for
that running level (see Fig 1). In comparison to the consensus for the importance of shoe fea-
tures (75%), the threshold for consensus was set lower for agreement on footwear feature prop-
erties (51%) because of the greater number of available response options.
Additional Delphi questions
In the second-round of the Delphi study, we aimed to quantify why the participants chose
“I don’t know” for the footwear feature properties. The participants were prompted to
choose one of the following if they selected “I don’t know”: feature is not well defined, fea-
ture is dependent on foot contact pattern (e.g. heel strike), feature is dependent on bio-
mechanical variables (e.g. foot inversion), feature has interplaying effects with other shoe
features, feature function is not known or other. These questions were included due to a
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
5 / 17
high frequency of “I don’t know” responses for some footwear feature properties. These
questions were only included in the second-round as we received feedback that the ques-
tionnaire was time consuming, which may have increased drop-out rate if included in the
third-round.
Fig 1. Flowchart describing the consensus and verifying consensus process for different shoe feature properties (XX) for
each running level (YY). The participants were asked to provide feedback for the recommended properties for all runner levels
on all 20 shoe features (XX1). In the second- and third-rounds, the participants were asked to provide feedback for the
recommended properties for all runner levels on the important shoe features and any additional shoe features the participants
recommended (XX2/3).
https://doi.org/10.1371/journal.pone.0236047.g001
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
6 / 17
Statistical analysis and visualization
Paired statistical analyses were performed to determine if the running level definitions
improved through the three rounds of this Delphi study. A Friedman’s test was performed uti-
lizing the subjective ratings from the respondents that participated in all three rounds of the
study (N = 24). If the Friedman’s test revealed a significant effect, follow-up Wilcoxon signed-
rank tests with a Bonferroni correction were performed to investigate pairwise differences
between the individual rounds. The significance level α was set to 0.05 for all statistical tests.
The median and inter-quartile ranges of the participants’ responses were also computed from
the subjective ratings. These descriptive statistics were computed to demonstrate if the ratings
increased and if there was less variability in the responses. All analyses were performed in
MATLAB (version 2019a, MathWorks, Natick, MA, USA). Figures were created in MATLAB
and Adobe Illustrator (version 22.1, San Jose, CA, USA).
Results
Participation
Of the 142 experts initially contacted, 29 responded to the first-round of this Delphi study (Fig
2, Table 2). Twenty-five respondents participated in the second-round and 24 participated in
the third-round (Fig 2, Table 2). Note that one academic moved to industry from academia
between rounds one and two.
Running level definitions
The respondents’ rating of the running level definitions improved as the Delphi study pro-
gressed, χ2 (2, N = 24) = 13.95, p = 0.0009. The median rating increased each round and the
Fig 2. Participation in each round of this Delphi study.
https://doi.org/10.1371/journal.pone.0236047.g002
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
7 / 17
interquartile range decreased. For example, 69% of respondents rated the running level defini-
tions between 7 and 10 in the first-round which increased to 88% of respondents in the third-
round (see Fig 3). The increase in the running level scores between the first and third rounds
was statistically significant (p = 0.006). The increased running level ratings were accompanied
by changes to the running level definitions. The changes to the “novice” running level defini-
tion for the second-round were: increased running experience to one year and replaced “stress
management” with “enjoyment” for running motivation. The changes to the “recreational”
running level definition for the second-round were: increased running experience to greater
than one year and replaced “stress management” with “enjoyment” for running motivation.
The changes to the “high-caliber” running level definition for the second-round were:
increased running habits to >4 sessions/week and >50 km/week, replaced “stress manage-
ment” with “enjoyment” for running motivation, re-order the running motivation to 1) Com-
petition, 2) Improve general heath, and 3) Enjoyment, and re-order the priorities for footwear
design to 1) Improve performance, 2) Reduce injury risk, 3) Improve comfort. We also speci-
fied the running performance as males between the ages of 18 to 34. Subsequent changes to the
running level definitions were to ensure that the high caliber and recreational runner 5 km
and 10 km times were indicative of the respective marathon times. These updates resulted in
the final runner level definitions in Table 3.
Footwear features
Twelve of the 20 footwear features reached the level of consensus to be considered important.
The majority (92%) of the second-round respondents rated the appropriateness of the 12
important footwear features as a 7/10 or higher. “Lacing system” was added to the second-
round of this Delphi study as five first-round respondents suggested that it should be included
in the list of footwear features. This feature did not reach the threshold of consensus in the sec-
ond-round (68%, Table 4) to be considered important. “Toe spring” was initially not an
important footwear feature as only 19/29 (66%, Table 4) first-round respondents thought it
was important for footwear design. Five second-round participants suggested to add “toe
spring” back into the survey (as it was removed because it was below the threshold of consen-
sus) and 22/24 (92%, Table 4) third-round participants thought that it was important for foot-
wear design.
Table 2. Number of participants and their experience investigating/designing footwear.
Experience (yrs)
Round 1
Round 2
Round 3
Academic
2–5
1
0
0
5–10
6
4
4
10+
8
7
7
Professional in the footwear industry
2–5
0
1
1
5–10
2
2
2
10+
8
8
8
Clinician
10+
2
1
1
Journalist
5–10
1
1
0
Coach
10+
1
1
1
Total
29
25
24
Note that one academic moved to industry between the first and second rounds of this study.
https://doi.org/10.1371/journal.pone.0236047.t002
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
8 / 17
Fig 3. Subjective rating of the running level definitions for the three rounds of this Delphi study. Changes in
subjective ratings were accompanied by updating the running levels definition based on respondents’ feedback. The
diamonds represent the median of each round and the bars indicate the interquartile range. Each shaded dot indicates
one response made by a respondent. The asterisk () indicates a statistical difference in the subjective ratings
(p = 0.006).
https://doi.org/10.1371/journal.pone.0236047.g003
Table 3. Final running level definitions.
Level 1
Novice
Level 2
Recreational
Level 3
High caliber
Running experience
Less than one year of regular
running experience
More than one year of regular
running experience
More than three years of regular
running experience
Running habits
0–3 sessions / week
1–5 sessions / week
> 4 sessions / week
5–20 km / week
15–50 km / week
> 50 km / week
Running performance (example times are for
male runners age 18–34)
5km time > 30 min OR
5km time > 21 min OR
5 km time 15–20 min$ OR
10km time > 60 min
10km time > 42 min OR
10 km time 30–42 min$ OR
No marathon racing
Marathon time 3–4.5 h
Marathon time <3h$
Running motivation (ordered according to
importance)
Improve general health
Improve general health
Competition
Enjoyment
Enjoyment
Improve general health
Weight management
Team affiliation
Enjoyment
Priorities for footwear design (from high to
low)
1) Improve comfort
1) Improve comfort
1) Improve performance
2) Reduce injury risk
2) Reduce injury risk
2) Reduce injury risk
3) Improve performance
3) Improve performance
3) Improve comfort
These definitions were refined by the Delphi study participants through the three rounds of feedback. The () indicates regular running experience defined as running at
least once per week. The ($) indicates that elite runners with faster race times than high caliber runners were not considered since they represent a small percentage of
the population and may require individual running footwear recommendations. Bolded characteristics indicate characteristics that changed from the first characteristics
presented to the respondents (Table 1).
https://doi.org/10.1371/journal.pone.0236047.t003
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
9 / 17
Footwear feature properties
Twenty-three of the 36 shoe feature properties (3 running levels x 12 important shoe features)
reached the 51% consensus threshold (Table 5). Consensus was obtained for upper breathabil-
ity, heel-to-toe drop, forefoot bending stiffness, crash pad and torsional bending stiffness for
all three running levels (Table 5). The consensus for the feature properties from the first- and
second-rounds was verified in the second- and third-rounds, respectively (Table 5). There was
no consensus for the properties of the toe spring as well as the rearfoot and forefoot midsole
hardness for any of the running levels (Table 5). The most frequent response regarding fore-
foot and rearfoot midsole hardness was “I don’t know”. In the second-round when participants
were asked further about this response, the most frequent answer (4/10 participants) for the
forefoot midsole hardness was “feature function is not known”. The responses for the rearfoot
midsole hardness were spread across the six different responses (see Methods: Additional Del-
phi Questions for full list of possible responses).
Discussion
This study provides a unique perspective of footwear experts, most of whom have been exam-
ining this topic for 10+ years. These experts indicated that 12 of the 21 footwear features were
important for footwear design with respect to different running levels. Experts came to a con-
sensus on the properties for five footwear features for all three running levels. Furthermore,
this study has highlighted footwear features that experts consider important but have received
little scientific attention, such as: upper breathability, forefoot bending stiffness, heel-to-toe
drop, torsional bending stiffness and crash pad (Fig 4). Future, novel research can be per-
formed with these features to add to the collective knowledge of how footwear features can
affect the running biomechanics of runners from different levels.
Interestingly, participants in this Delphi study did not come to a consensus for the recom-
mended footwear properties for some of the most researched shoe features: forefoot and rear-
foot midsole hardness [12,13]. Previous research has shown that a softer rearfoot midsole can
reduce ground reaction force loading metrics such as vertical loading rate or peak impact
forces [25–27], which have been hypothesized to reduce running-related injuries [28,29]. The
causal relationship between ground reaction force loading metrics and running-related inju-
ries has not been established. Furthermore, examining prospective running injury studies
Table 4. Percent of participants that agreed upon the importance of shoe features.
Shoe Feature
% Participants
Shoe Feature
% Participants
Shoe Mass
100
Toe Spring
66/92
Upper Breathability
97
Heel Counter
72
Forefoot Midsole Hardness
93
Medial Post
72
Rearfoot Midsole Hardness
93
Midfoot Bending Stiffness
72
Heel (stack) Height
90
Upper Elasticity
72
Midsole Thickness
86
Insole Shape
69
Forefoot Bending Stiffness
83
Lacing System
68
Outsole Traction
83
Rocker
59
Heel-to-Toe Drop
79
Heel Flares
55
Torsional Bending Stiffness
79
Forefoot Flares
45
Crash Pad
76
The shoe features with a consensus above 75% were considered important (bolded). The toe spring was initially not considered important (consensus: 66%), but was
considered important in the third-round (consensus: 92%). The lacing system was added in the second-round to the study, but was not considered important.
https://doi.org/10.1371/journal.pone.0236047.t004
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
10 / 17
together demonstrates that ground reaction force loading metrics are not related to injuries
[30–40]. This paradigm shift could be the reason for the high frequency of “I don’t know”
responses for the recommended properties for the forefoot and rearfoot midsole hardness,
with the most frequent feedback being “the feature function is not known”. Additionally,
shoe midsole hardness may interplay with other shoe features such as heel (stack) height or
heel-to-toe drop to affect the overall shoe cushioning. This interplay could be the reason for
inconsistent findings across studies examining midsole hardness [25,41,42]. In total, further
Table 5. Shoe feature properties that were most frequently chosen for each running level.
Shoe Feature
Running Level
Recommended Property
Round
% Participants
% Participants in agreement with consensus
Shoe Mass
Novice
225–275 g
3
43
-
Recreational
225–275 g
3
54
-
High Caliber
<175 g
1
59
72
Upper Breathability
Novice
High Breathability
1
69
100
Recreational
High Breathability
1
79
100
High Caliber
High Breathability
1
86
100
Forefoot Midsole Hardness
Novice
I don’t know
3
50
-
Recreational
I don’t know
3
50
-
High Caliber
I don’t know
3
42
-
Rearfoot Midsole Hardness
Novice
I don’t know
3
42
-
Recreational
I don’t know
3
42
-
High Caliber
I don’t know
2
48
-
Heel (stack) Height
Novice
14–32 mm
2
72
88
Recreational
14–32 mm
1
65
88
High Caliber
14–32 mm
3
42
-
Midsole Thickness
Novice
10–15 mm
2
60
58
Recreational
10–15 mm
2
52
71
High Caliber
10–15 mm
3
50
-
Forefoot Bending Stiffness
Novice
Low Stiffness
1
55
64
Recreational
Medium Stiffness
1
66
100
High Caliber
High Stiffness
1
55
84
Outsole Traction
Novice
Medium Traction
1
52
76
Recreational
Medium Traction
1
55
72
High Caliber
Medium Traction
3
50
-
Heel-to-Toe Drop
Novice
8–12 mm
2
56
88
Recreational
8–12 mm
3
58
-
High Caliber
4–8 mm
3
71
-
Torsional Bending Stiffness
Novice
Medium Stiffness
2
72
92
Recreational
Medium Stiffness
1
52
76
High Caliber
Medium Stiffness
2
52
88
Crash Pad
Novice
Include Crash Pad
1
76
88
Recreational
Include Crash Pad
1
72
88
High Caliber
Include Crash Pad
3
58
-
Toe Spring
Novice
Mid (16–30 deg)
1
34
-
Recreational
Mid (16–30 deg)
3
38
-
High Caliber
I don’t know
1
34
-
“Round” indicates which round of the Delphi study provided the highest consensus. The footwear feature properties that were above the consensus threshold for
Rounds 1 and 2 were all verified in the subsequent rounds as indicated by the percent agreed with consensus (last column).
https://doi.org/10.1371/journal.pone.0236047.t005
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
11 / 17
investigations are warranted to determine the biomechanical function of the midsole hardness
during running and its relationship with running-related injuries. To achieve this goal, future
studies should focus on how footwear properties affect the internal forces (e.g. muscle, tendon,
or bone forces) that act on the structures at risk of injury during running [8,43].
Though the experts did provide opinions regarding property ranges for different footwear
features, there should be considerations for how these features affect runners and how these
features interact. Studies have shown that subject-specific tuning of the forefoot longitudinal
bending stiffness can improve running performance [4,44]. Utilizing the expert opinions for
groups of runners may overlook this aspect that might be a consideration for footwear design.
On the other hand, tuning of multiple features together (e.g. midsole hardness, longitudinal
bending stiffness) can provide benefits across a wide range of runners as exemplified by the
Nike Vaporfly [19,45]. Such interplay was not addressed in our study as it would exponentially
complicate the survey provided to the participants. However, the respondents had mentioned
(in feedback and in responses to the round 2 survey, see the S2 Appendix for full responses)
that it is difficult to consider some of these footwear features in isolation.
The footwear experts came to a consensus on the running level definitions through slight
adjustments to the initial definitions proposed and derived from literature. We opted to pro-
vide initial running level definitions to our expert panel rather than letting the panel formulate
the definitions independently. This latter approach would have required additional Delphi
Fig 4. Footwear feature importance and the number of related publications. Footwear feature importance as rated
by experts in this study in comparison to the number of available publications for each footwear feature based on a
recent literature review (with permission from [13]). The footwear features inside the box represent opportunities for
future footwear research: while these features were deemed important by footwear experts, only few publications exist
regarding how these features affect runners from different levels.
https://doi.org/10.1371/journal.pone.0236047.g004
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
12 / 17
rounds prior to the recommendation of footwear features and their properties. Panel formu-
lated definitions may have resulted in different running level definitions compared to the
approach presented here. Different running level definitions could have led to altered footwear
feature recommendations. However, the experts’ consensus on the running level definitions
was in agreement with prior literature. This is exhibited by the novice runner level definition
which is similar to a definition created based on subjective running questionnaires [7]. These
definitions may be viewed more as guidelines as one footwear expert mentioned that “Even
elite athletes perform training runs with different intensities, durations, on different surfaces
and so on. For each of these runs they might select a different type of footwear.” This comment
touches on the competing requirements for running shoes as there may be multiple “correct”
shoes for a given running level, especially in the high caliber category.
The Delphi methodology is a useful tool for understanding the current status of a given
research area, as understood by experts in the field [46]. As such, results from this study can
be leveraged to 1) determine if experts are correct in their assumptions (e.g. high forefoot
bending stiffness for high caliber runners), 2) determine important areas of limited research
and 3) demonstrate areas where there is a lot of research, but little consensus (e.g. rearfoot
midsole hardness). The relatively low drop out rate (17%) in conjunction with the extensive
feedback obtained from the respondents via open ended questions provides confidence in
our methodological approach. The Delphi methodology appears to be relevant when explor-
ing high level topics related to running, and identifying the areas where further research is
required.
There are several limitations to acknowledge with this study. Consensus on the recom-
mended footwear feature properties from the third-round could not be confirmed as there was
no fourth-round. We believe that the third-round consensus would have been confirmed as
the consensus from the first- and second-rounds were confirmed in the second- and third-
rounds, respectively. During the second- and third-rounds of the Delphi study, we aimed to
reduce the time it took to complete the survey to limit the drop-out rate. To do so, we elimi-
nated footwear features that were not considered important (consensus below 75%) and elimi-
nated footwear feature properties once they were confirmed. Without such eliminations, a
different consensus may have been obtained, but there may have also been a larger drop out
rate due to the lengthy and repetitive survey. It is recommended to have a drop out rate of less
than 30% [47]. We attained a drop out rate of 17%. Additionally, we did not specify whether
the footwear recommendations were for male or female runners. As such, these results may
not be generalizable between male and female runners as they show distinct anthropometrics
and movement mechanics [48]. These results may also not be generalizable to different run-
ning surfaces/terrains as we asked participants to only consider running on a hard surface.
Furthermore, the final recommendations may be biased as the majority of experts were male
(e.g. 22/26 of the final participants). This expert panel was otherwise diverse as nine countries
were represented. The recommended footwear feature properties may have been influenced by
a dynamic definition of the runner levels, which changed slightly throughout the study. These
changing definitions seemed to have little effect on expert opinions on the footwear feature
properties as the verifying consensus level was generally higher than the original consensus
level (Table 4, last vs. second-to-last column). We also did not specify to the experts how many
of the of the categories a runner must match to be considered a “novice”, “recreational” or
“high caliber” runner. This may have led to minor variations in expert recommendations.
Lastly, the data presented here reflect opinions of experts that have experience with footwear.
As such, the findings from this study can serve as a valuable starting point for future systematic
biomechanical investigations.
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
13 / 17
Conclusion
Footwear experts provided feedback on the effects of different footwear features on running
biomechanics across three running levels. These experts also came to a consensus on the char-
acteristics of runners in these different running levels. The footwear experts indicated that 12
of the 21 footwear features were important for footwear design. Of these 12 features, experts
were able to come to a consensus for five footwear feature properties for all three running lev-
els. These features were: upper breathability, forefoot bending stiffness, heel-to-toe drop, tor-
sional bending stiffness and crash pad. Interestingly, the experts were not able to come to a
consensus for one of the most researched footwear features, i.e. rearfoot midsole hardness.
These recommendations can provide a starting point for further biomechanical studies, espe-
cially for features that have not yet been examined experimentally, e.g. upper breathability.
Supporting information
S1 Appendix. Shoe feature descriptions and properties.
(DOCX)
S2 Appendix. Raw data from the Delphi study.
(XLSX)
Acknowledgments
We would like to thank all of the participants who gave their time to complete the three rounds
of this Delphi study including: Michael Asmussen, Christopher Bishop, Jason Bonacci, Nicho-
las Delattre, Cedric Morio, Tim Derrick, Ned Frederick, Marlene Giandolini, Allison Gruber,
Bryan Heiderscheit, Laurent Malisoux, Sabina Manz, Frank Bichel, Benno Nigg, Max Paquette,
Craig Payne, Natsuki Sate, Thorsten Sterzing, Matthieu Trudeau, Steffen Willwacher, Beat
Hintermann, and Helen Woo. We would also like to thank Ross Miller regarding discussions
about prospective studies examining ground reaction force metrics.
Author Contributions
Conceptualization: Maurice Mohr, Wing-Kai Lam, Sandro Nigg.
Data curation: Eric C. Honert, Sandro Nigg.
Formal analysis: Eric C. Honert.
Investigation: Eric C. Honert.
Methodology: Maurice Mohr, Wing-Kai Lam.
Software: Sandro Nigg.
Supervision: Wing-Kai Lam, Sandro Nigg.
Validation: Eric C. Honert.
Writing – original draft: Eric C. Honert.
Writing – review & editing: Eric C. Honert, Maurice Mohr, Wing-Kai Lam, Sandro Nigg.
References
1.
Mu¨ndermann A, Stefanyshyn DJ, Nigg BM. Relationship between footwear comfort of shoe inserts and
anthropometric and sensory factors. Med Sci Sports Exerc. 2001; 33: 1939–1945. https://doi.org/10.
1097/00005768-200111000-00021 PMID: 11689747
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
14 / 17
2.
Reinschmidt C, Nigg BM. Current Issues in the Design of Running and Court Shoes. Sportverletz 
Sportschaden. 2000; 14: 72–81. https://doi.org/10.1055/s-2000-7866 PMID: 11081243
3.
Roy J-PR, Stefanyshyn DJ. Shoe Midsole Longitudinal Bending Stiffness and Running Economy, Joint
Energy, and EMG. Med Sci Sports Exerc. 2006; 38: 562–569. https://doi.org/10.1249/01.mss.
0000193562.22001.e8 PMID: 16540846
4.
Stefanyshyn DJ, Fusco C. Increased shoe bending stiffness increases sprint performance. Sports Bio-
mech. 2004; 3: 55–66. https://doi.org/10.1080/14763140408522830 PMID: 15079988
5.
Trudeau MB, Willwacher S, Weir G, Rohr E, Ertel C, Bruggemann G-P, et al. A novel method for esti-
mating an individual’s deviation from their habitual motion path when running. Footwear Sci. 2019; 0: 1–
11. https://doi.org/10.1080/19424280.2019.1615004
6.
Clifton P, Subic A, Burton M, Bedford A, Schembri A. FUNCTIONAL CHARACTERISTICS OF RUN-
NING SHOES FOR DIFFERENT USER GROUPS. Seoul, Korea; 2013. p. 10.
7.
Besomi M, Leppe J, Silvestre MCD, Setchell J. SeRUN® study: Development of running profiles using a
mixed methods analysis. PLOS ONE. 2018; 13: e0200389. https://doi.org/10.1371/journal.pone.
0200389
8.
Nigg BM, Mohr M, Nigg SR. Muscle tuning and preferred movement path—a paradigm shift. Curr
Issues Sport Sci CISS. 2017; 0.
9.
Videbæk S, Bueno AM, Nielsen RO, Rasmussen S. Incidence of Running-Related Injuries Per 1000 h
of running in Different Types of Runners: A Systematic Review and Meta-Analysis. Sports Med. 2015;
45: 1017–1026. https://doi.org/10.1007/s40279-015-0333-8 PMID: 25951917
10.
Theisen D, Malisoux L, Genin J, Delattre N, Seil R, Urhausen A. Influence of midsole hardness of stan-
dard cushioned shoes on running-related injury risk. Br J Sports Med. 2014; 48: 371–376. https://doi.
org/10.1136/bjsports-2013-092613 PMID: 24043665
11.
Jakobsen BW, Kro´ner K, Schmidt SA, Kjeldsen A. Prevention of injuries in long-distance runners. Knee
Surg Sports Traumatol Arthrosc. 1994; 2: 245–249. https://doi.org/10.1007/BF01845597 PMID:
8536050
12.
Sun X, Lam W-K, Zhang X, Wang J, Fu W. Systematic Review of the Role of Footwear Constructions in
Running Biomechanics: Implications for Running-Related Injury and Performance. J Sports Sci Med.
2020; 19: 20–37. PMID: 32132824
13.
Hoitz F, Mohr M, Asmussen M, Lam W-K, Nigg S, Nigg B. The effects of systematically altered foot-
wear features on biomechanics, injury, performance, and preference in runners of different skill
level: a systematic review. Footwear Sci. 2020; 0: 1–23. https://doi.org/10.1080/19424280.2020.
1773936
14.
Esculier J-F, Dubois B, Dionne CE, Leblond J, Roy J-S. A consensus definition and rating scale for mini-
malist shoes. J Foot Ankle Res. 2015; 8: 42. https://doi.org/10.1186/s13047-015-0094-5 PMID:
26300981
15.
Malisoux L, Chambon N, Urhausen A, Theisen D. Influence of the Heel-to-Toe Drop of Standard Cush-
ioned Running Shoes on Injury Risk in Leisure-Time Runners: A Randomized Controlled Trial With 6-
Month Follow-up. Am J Sports Med. 2016; 44: 2933–2940. https://doi.org/10.1177/0363546516654690
PMID: 27501833
16.
Tay CS, Sterzing T, Lim CY, Ding R, Kong PW. Overall Preference of Running Shoes Can Be Predicted
by Suitable Perception Factors Using a Multiple Regression Model. Hum Factors. 2017; 59: 432–441.
https://doi.org/10.1177/0018720816681147 PMID: 28430546
17.
Malisoux L, Nielsen RO, Urhausen A, Theisen D. A step towards understanding the mechanisms of run-
ning-related injuries. J Sci Med Sport. 2015; 18: 523–528. https://doi.org/10.1016/j.jsams.2014.07.014
PMID: 25174773
18.
Cavanagh PR, Pollock ML, Landa J. A Biomechanical Comparison of Elite and Good Distance Runners.
Ann N Y Acad Sci. 1977; 301: 328–345. https://doi.org/10.1111/j.1749-6632.1977.tb38211.x PMID:
270926
19.
Hoogkamer W, Kipp S, Frank JH, Farina EM, Luo G, Kram R. A Comparison of the Energetic Cost of
Running in Marathon Racing Shoes. Sports Med. 2018; 48: 1009–1019. https://doi.org/10.1007/
s40279-017-0811-2 PMID: 29143929
20.
de Ruiter CJ, Verdijk PWL, Werker W, Zuidema MJ, de Haan A. Stride frequency in relation to oxygen
consumption in experienced and novice runners. Eur J Sport Sci. 2014; 14: 251–258. https://doi.org/10.
1080/17461391.2013.783627 PMID: 23581294
21.
Fuller JT, Thewlis D, Tsiros MD, Brown NAT, Buckley JD. Effects of a minimalist shoe on running econ-
omy and 5-km running performance. J Sports Sci. 2016; 34: 1740–1745. https://doi.org/10.1080/
02640414.2015.1136071 PMID: 27328725
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
15 / 17
22.
Cook C, Brisme´e J-M, Fleming R, Sizer PS. Identifiers Suggestive of Clinical Cervical Spine Instability:
A Delphi Study of Physical Therapists. Phys Ther. 2005; 85: 895–906. https://doi.org/10.1093/ptj/85.9.
895 PMID: 16117600
23.
Binkley J, Finch E, Hall J, Black T, Gowland C. Diagnostic Classification of Patients with Low Back
Pain: Report on a Survey of Physical Therapy Experts. Phys Ther. 1993; 73: 138–150. https://doi.org/
10.1093/ptj/73.3.138 PMID: 8438002
24.
Loughlin KG, Moore LF. Using Delphi to achieve congruent objectives and activities in a pediatrics
department. J Med Educ. 1979; 54: 101–106. https://doi.org/10.1097/00001888-197902000-00006
PMID: 762686
25.
Baltich J, Maurer C, Nigg BM. Increased Vertical Impact Forces and Altered Running Mechanics with
Softer Midsole Shoes. PLoS ONE. 2015; 10. https://doi.org/10.1371/journal.pone.0125196 PMID:
25897963
26.
Sterzing T, Schweiger V, Ding R, Cheung JT-M, Brauner T. Influence of rearfoot and forefoot midsole
hardness on biomechanical and perception variables during heel-toe running. Footwear Sci. 2013; 5:
71–79. https://doi.org/10.1080/19424280.2012.757810
27.
Nigg BM, Morlock M. The influence of lateral heel flare of running shoes on pronation and impact forces.
Med Sci Sports Exerc. 1987; 19: 294–302. PMID: 3600244
28.
Messier SP, Davis SE, Curl WW, Lowery RB, Pack RJ. Etiologic factors associated with patellofemoral
pain in runners. Med Sci Sports Exerc. 1991; 23: 1008–1015. PMID: 1943620
29.
van der Worp H, Vrielink JW, Bredeweg SW. Do runners who suffer injuries have higher vertical ground
reaction forces than those who remain injury-free? A systematic review and meta-analysis. Br J Sports
Med. 2016; 50: 450–457. https://doi.org/10.1136/bjsports-2015-094924 PMID: 26729857
30.
Nigg BM, Baltich J, Hoerzer S, Enders H. Running shoes and running injuries: mythbusting and a pro-
posal for two new paradigms: ‘preferred movement path’ and ‘comfort filter’. Br J Sports Med. 2015; 49:
1290–1294. https://doi.org/10.1136/bjsports-2015-095054
31.
Dudley RI, Pamukoff DN, Lynn SK, Kersey RD, Noffal GJ. A prospective comparison of lower extremity
kinematics and kinetics between injured and non-injured collegiate cross country runners. Hum Mov
Sci. 2017; 52: 197–202. https://doi.org/10.1016/j.humov.2017.02.007 PMID: 28237655
32.
Napier C, MacLean CL, Maurer J, Taunton JE, Hunt MA. Kinetic risk factors of running-related injuries
in female recreational runners. Scand J Med Sci Sports. 2018; 28: 2164–2172. https://doi.org/10.1111/
sms.13228 PMID: 29846979
33.
Gerlach KE, White SC, Burton HW, Dorn JM, Leddy JJ, Horvath PJ. Kinetic Changes with Fatigue and
Relationship to Injury in Female Runners. Med Sci Sports Exerc. 2005; 37: 657–663. https://doi.org/10.
1249/01.mss.0000158994.29358.71 PMID: 15809566
34.
Bredeweg SW, Kluitenberg B, Bessem B, Buist I. Differences in kinetic variables between injured and
noninjured novice runners: A prospective cohort study. J Sci Med Sport. 2013; 16: 205–210. https://doi.
org/10.1016/j.jsams.2012.08.002 PMID: 22921763
35.
Messier SP, Martin DF, Mihalko SL, Ip E, DeVita P, Cannon DW, et al. A 2-Year Prospective Cohort
Study of Overuse Running Injuries: The Runners and Injury Longitudinal Study (TRAILS). Am J Sports
Med. 2018; 46: 2211–2221. https://doi.org/10.1177/0363546518773755 PMID: 29791183
36.
Davis IS, Bowser BJ, Mullineaux DR. Greater vertical impact loading in female runners with medically
diagnosed injuries: a prospective investigation. Br J Sports Med. 2016; 50: 887–892. https://doi.org/10.
1136/bjsports-2015-094579 PMID: 26644428
37.
Kuhman DJ, Paquette MR, Peel SA, Melcher DA. Comparison of ankle kinematics and ground reaction
forces between prospectively injured and uninjured collegiate cross country runners. Hum Mov Sci.
2016; 47: 9–15. https://doi.org/10.1016/j.humov.2016.01.013 PMID: 26827155
38.
Nigg BM, Cole GK, Bru¨ggemann G-P. Impact Forces during Heel-Toe Running. J Appl Biomech. 1995;
11: 407–432.
39.
Willems TM, Witvrouw E, De Cock A, De Clercq D. Gait-Related Risk Factors for Exercise-Related
Lower-Leg Pain during Shod Running. Med Sci Sports Exerc. 2007; 39: 330–339. https://doi.org/10.
1249/01.mss.0000247001.94470.21 PMID: 17277598
40.
Stefanyshyn DJ, Stergiou P, Lun VMY, Meeuwisse WH. Dynamic Variables and Injuries in Running.
Proceedings of the 5th Symposium on Footwear Biomechanics. Zuerich, Switzerland; 2001.
41.
Hamill J, Russell EM, Gruber AH, Miller R. Impact characteristics in shod and barefoot running. Foot-
wear Sci. 2011; 3: 33–40. https://doi.org/10.1080/19424280.2010.542187
42.
Clarke TE, Frederick EC, Cooper LB. Effects of Shoe Cushioning Upon Ground Reaction Forces in
Running. Int J Sports Med. 1983; 04: 247–251. https://doi.org/10.1055/s-2008-1026043 PMID:
6654550
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
16 / 17
43.
Tilp M. Nigg Benno M., Mohr Maurice M. & Nigg Sandro R.–New paradigms in running injury prevention.
Curr Issues Sport Sci. 2019;4. https://doi.org/10.15203/CISS_2019.100
44.
Oh K, Park S. The bending stiffness of shoes is beneficial to running energetics if it does not disturb the
natural MTP joint flexion. J Biomech. 2017; 533: 127–135. https://doi.org/10.1016/j.jbiomech.2017.01.
014 PMID: 28168959
45.
Barnes KR, Kilding AE. A Randomized Crossover Study Investigating the Running Economy of Highly-
Trained Male and Female Distance Runners in Marathon Racing Shoes versus Track Spikes. Sports
Med. 2019; 49: 331–342. https://doi.org/10.1007/s40279-018-1012-3 PMID: 30374945
46.
Hasson F, Keeney S. Enhancing rigour in the Delphi technique research. Technol Forecast Soc
Change. 2011; 78: 1695–1704. https://doi.org/10.1016/j.techfore.2011.04.005
47.
Sumsion T. The Delphi Technique: An Adaptive Research Tool. Br J Occup Ther. 1998; 61: 153–156.
https://doi.org/10.1177/030802269806100403
48.
Ferber R, McClay Davis I, Williams DS III. Gender differences in lower extremity mechanics during run-
ning. Clin Biomech. 2003; 18: 350–357. https://doi.org/10.1016/S0268-0033(03)00025-1
PLOS ONE
Shoe feature recommendations for different running levels
PLOS ONE | https://doi.org/10.1371/journal.pone.0236047
July 16, 2020
17 / 17

Shoe feature recommendations for different running levels: A Delphi study.
Honert, Eric C,Mohr, Maurice,Lam, Wing-Kai,Nigg, Sandro