STUDY PROTOCOL
Open Access
Protocol for evaluating the effects of a
therapeutic foot exercise program on injury
incidence, foot functionality and
biomechanics in long-distance runners:
a randomized controlled trial
Alessandra B. Matias1, Ulisses T. Taddei1, Marcos Duarte2 and Isabel C. N. Sacco1*
Abstract
Background: Overall performance, particularly in a very popular sports activity such as running, is typically
influenced by the status of the musculoskeletal system and the level of training and conditioning of the biological
structures. Any change in the musculoskeletal system’s biomechanics, especially in the feet and ankles, will strongly
influence the biomechanics of runners, possibly predisposing them to injuries. A thorough understanding of the
effects of a therapeutic approach focused on feet biomechanics, on strength and functionality of lower limb
muscles will contribute to the adoption of more effective therapeutic and preventive strategies for runners.
Methods/Design: A randomized, prospective controlled and parallel trial with blind assessment is designed to
study the effects of a "ground-up" therapeutic approach focused on the foot-ankle complex as it relates to the
incidence of running-related injuries in the lower limbs. One hundred and eleven (111) healthy long-distance
runners will be randomly assigned to either a control (CG) or intervention (IG) group. IG runners will participate in a
therapeutic exercise protocol for the foot-ankle for 8 weeks, with 1 directly supervised session and 3 remotely
supervised sessions per week. After the 8-week period, IG runners will keep exercising for the remaining 10 months
of the study, supervised only by web-enabled software three times a week. At baseline, 2 months, 4 months and
12 months, all runners will be assessed for running-related injuries (primary outcome), time for the occurrence of
the first injury, foot health and functionality, muscle trophism, intrinsic foot muscle strength, dynamic foot arch
strain and lower-limb biomechanics during walking and running (secondary outcomes).
Discussion: This is the first randomized clinical trial protocol to assess the effect of an exercise protocol that was
designed specifically for the foot-and-ankle complex on running-related injuries to the lower limbs of long-distance
runners. We intend to show that the proposed protocol is an innovative and effective approach to decreasing the
incidence of injuries. We also expect a lengthening in the time of occurrence of the first injury, an improvement in
foot function, an increase in foot muscle mass and strength and beneficial biomechanical changes while running
and walking after a year of exercising.
(Continued on next page)
* Correspondence: icnsacco@usp.br
1Department of Physical Therapy, Speech, and Occupational Therapy, School
of Medicine, University of São Paulo, Rua Cipotânea, 51 - Cidade Universitária,
05360-160 São Paulo, São Paulo, Brazil
Full list of author information is available at the end of the article
© 2016 Matias et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
DOI 10.1186/s12891-016-1016-9
(Continued from previous page)
Trial registration: Clinicaltrials.gov Identifier NCT02306148 (November 28, 2014) under the name “Effects of Foot
Strengthening on the Prevalence of Injuries in Long Distance Runners”. Committee of Ethics in Research of the School
of Medicine of the University of Sao Paulo (18/03/2015, Protocol # 031/15).
Keywords: Running, Sports injuries, Exercise therapy, Foot, Biomechanics
Background
Human performance, particularly in one of the most
popular sports activities such as running, is typically influ-
enced by the state of the musculoskeletal system, either by
the level of training and conditioning of the biological
structures, or by the aging process. Although popular
worldwide due to its low cost, versatility, convenience [1],
and health benefits to people of all ages [2], running is as-
sociated with a high prevalence of lower extremity injuries
(between 19.4 and 79.3 %) [3]. The occurrence of injuries
limits the intended benefits by inducing changes in prac-
tice habits [4] or temporary or even permanent cessation
of running. In addition, injuries lead to increased costs
due to medical treatment and/or work absence [5].
The understanding of risk factors associated with these
injuries, particularly the intrinsic factors, can provide
important benefits for runners. Among these intrinsic
factors, those that are noteworthy include biomechanical
factors and muscle functionality of the lower extremities,
particularly the feet. A systematic review by van der
Worp et al. [5] included 11 high-quality longitudinal
studies and concluded that alterations in the biomechan-
ical force distribution patterns, amount of training, his-
tory of previous injuries, increased index of the navicular
drop, and the misalignment of the ankle, knee, and hip
are among the main intrinsic risk factors for running-
related injuries. In addition, extrinsic factors such as the
training surface and the type of footwear are also relevant
risk factors [5]. It is noteworthy that out of these seven di-
verse risk factors, two are related to the foot-ankle com-
plex, demonstrating the importance of maintaining the
health and functionality of its musculoskeletal structures
to prevent injuries. It is also believed that any biomechan-
ical alteration in the musculoskeletal system, in particular
the foot-ankle complex, broadly influences a runner’s
functionality, predisposing him/her to a lesser or greater
extent to injuries, in addition to the possibility of com-
promising his/her quality of life [2, 6].
The foot has a complex structure that can perform a
broad variety of functions in different postural and dy-
namic tasks [7, 8]. This versatility can only be achieved
through its unique arch-shaped architecture and its
powerful intrinsic and extrinsic muscular activity, which
is responsible for the maintenance and control of foot
arches, postural corrections during disturbances, and
torque generation during body displacement [9, 10].
Even with this unique and specialized structure, a high
prevalence of injuries associated with running practices
occurs in this complex. Among the most common hy-
potheses used to explain this high prevalence are factors
such as the excessive ankle/foot pronation in the stance
phase of running [11], the lowering of the medial longi-
tudinal arch due to navicular drop [12, 13], the alteration
of rigidity of the plantar arches [14], and the increase in
impact and acceleration of the tibia during running [15].
Evidence suggests the importance of the intrinsic foot
musculature, showing that fatigue can cause a significant
increase in pronation, which is evaluated by the navicu-
lar drop [12]. In addition, weakness may be a risk factor
for falls in the elderly population [16]. Therefore, it is
understandable that the specific training of foot [13, 17]
and ankle muscles [18–20] is an important tool that im-
proves functions and functionalities of the lower extrem-
ities, as has been shown in recent studies [13, 19–21].
In one of those studies, the unsupervised practice of a
single exercise for the feet (short-foot exercise) four
times a week promoted a decrease in the navicular drop,
an increase in the medial longitudinal arch index, and an
increase in the functionality quality of the intrinsic foot
muscles in asymptomatic individuals [13]. These results
were maintained 1 month after the training had been
completed. Although the results of Mulligan and Cook
[13] are promising, they only measured the foot function
in static conditions and the unsupervised practice of an
isolated exercise for 4 weeks may not have been suffi-
cient to cause a transfer of the static gains for a more
dynamic task where the foot would be more robustly
utilized, according to the star excursion balance test. In
contrast, one study compared two groups: one group
performed a 4-week period of short-foot exercises, in-
cluding 100 repetitions for five seconds each, and the
second group performed a 4-week period of towel-curl
exercises with the same amount of exercise [20]. This
controlled study showed that both groups exhibited de-
creased displacement of the centre of pressure during
the modified star excursion test. Therefore, a load in-
crease in the same exercises used by Mulligan and Cook
[13] resulted in positive effects for postural control.
The same short-foot exercise was practiced by individ-
uals with flat feet in a randomized controlled trial to in-
vestigate its effect on the use of foot orthoses [17]. The
protocol consisted of three to five sets of exercises with
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 2 of 11
five repetitions each, twice a day, for 8 weeks. In both
study groups, the isometric force and the transversal sec-
tion area of the abductor hallucis muscle were increased
after the interventions, with a significant increase in the
group that used orthoses during exercises. These results
demonstrated that even in structurally unfavourable
conditions, exercise for the foot muscles leads to import-
ant strength gains. It is noteworthy that even with a well-
planned intervention, the lack of a control group and the
evaluation of the muscle strength alone limit the study
conclusions. In addition, the study did not take into ac-
count the potential clinical and functional changes of the
plantar arches, as performed by Goldmann et al. [19]. This
group of researchers investigated the effects of the hallucis
flexors strengthening in the kinetic and kinematic of foot
and ankle during walking, running, and vertical jumping
among university athletes. Training of the experimental
group consisted of isometric contractions of the hallucis
flexors at 90 % of the maximum voluntary contraction
using a dynamometer four times a week for 7 weeks. The
authors observed a significant increase in the performance
of vertical jumping and extensor and flexor momentum of
the metatarsal-phalangeal joint and a gain of 60 to 70 % in
the strength of the hallucis flexors. This study shows that
the flexor muscles of the foot respond in a quick and in-
tense manner to training; even for simple training, the
strengthening of the muscles in question results in global
kinematic and kinetic alterations. It would still be interest-
ing to determine how long these gains would last after the
completion of the intervention and whether more elabor-
ate training, involving more muscles and different pos-
tures and loads, would alter the study outcome, especially
with regard to foot biomechanics during locomotor tasks.
The understanding of the effects of a therapeutic ap-
proach focused on the foot biomechanics of walking and
running, on the strength and functionality of lower ex-
tremity muscles will contribute to the adoption of more
effective therapeutic and preventive strategies for runners.
However, no evidence exists that supports the efficacy of
the therapeutic exercises already used and recommended
for the health of the feet [7, 17, 19, 20, 22] with regard to
preventing recurrent injuries in long-distance runners.
However, one research protocol aims to assess the effects
of ankle and hip muscle strengthening and functional bal-
ance training on running mechanics, postural control, and
injury incidence in novice runners with less than 1 year of
running experience but without focusing on the interven-
tion of intrinsic and extrinsic muscles of the feet [23].
Therefore, a controlled and randomized clinical trial
would determine whether these interventions are effi-
cacious by using the incidence of running-related in-
juries as the primary outcome and following both
intervention and control subjects during a period of
time equal to or greater than 1 year (the period during
which the incidence and prevalence of these injuries
are reported) [4, 16, 24–27].
It is important to highlight that rehabilitation programs
rarely include the intrinsic muscles of the feet in their
therapeutic protocols. The present proposal uses a new
paradigm in which the focus of training and preventive in-
terventions in runners is a “ground-up” approach rather
than the traditional "top-down" approach, which focuses
on the hip strengthening. This new approach, advocated
by Baltich et al. [23], will seek to improve the function of
the ankle-foot complex, which is directly associated with
the absortion and transmission of body forces to the
ground and vice-versa during running.
Hypotheses
Our hypotheses are that the therapeutic exercise proto-
col for the foot-ankle as practiced by long-distance rec-
reational runners for 1 year will:
H 1. Reduce the incidence of running-related injury in
the lower limbs,
H 2. Lengthening the time for the occurrence of the
first running-related injury in the lower limbs,
H 3. Increase intrinsic foot muscle strength,
H 4. Increase foot muscle cross-sectional area and
volume,
H 5. Improve foot health and functionality status,
H 6. Reduce dynamic strain on the foot’s longitudinal
arch during running and walking, and
H 7. Produce beneficial biomechanical changes during
running that denote an improvement in the mechanical
efficiency of absorbing loads and propelling the body
while walking and running. Such changes would
include an increase in the ankle range of motion in the
sagittal plane and increases in 1) ankle extensor
moment and power and 2) knee extensor moment and
power during the second half of the stance phase.
Our aim is therefore to investigate the effects of a
"ground-up" therapeutic approach focused on the foot-
ankle for 1 year as they relate to 1) the incidence of
running-related injuries in the lower limbs of long-distance
runners, 2) time of occurrence of the first injury, 3) foot
health and functionality, 4) strength of the intrinsic foot
muscles; 5) foot muscle trophism, 6) dynamic foot arch
strain and 7) lower-limb biomechanics during walking and
running.
Methods/Design
Overview of the research design
A randomized, prospective controlled and parallel trial
with blind assessment is designed to study the effects of a
"ground-up" therapeutic approach focused on the foot-
ankle concerning the incidence of running-related injuries
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 3 of 11
to the lower limbs of long-distance runners. This trial has
an allocation ratio of 1:1. Its framework is exploratory to
gather preliminary information on the intervention of
conducting a full scale trial. The trial follows all recom-
mendations established by SPIRIT [28].
Long-distance recreational runners are recruited from
the vicinity of the city of São Paulo and referred to a
physical therapist, who performs the group allocation.
The participants are then referred to another physical
therapist, who performs the initial blind assessment. All
runners allocated to the intervention group (IG) partici-
pate in a protocol of therapeutic exercises for the foot-
ankle complex for 8 weeks, with one session per week
supervised by a physical therapist and three sessions per
week remotely supervised by web-enabled software [29].
They receive access to the web software on the first day
and use it for 8 weeks. After the 8-week period, the IG
runners will continue exercising for 10 more months,
supervised only by the web software three times a week.
The runners allocated to the control group (CG) do not
receive any intervention training, but receive a placebo
stretching exercise program.
All runners will be assessed at baseline and 2 months
(end of intervention). They are then assessed twice more
for follow-up purposes, at 4 and 12 months after the
baseline. Assessments will concern the incidence of
running-related injuries (primary outcome), and all other
secondary outcomes.
The design and flowchart of the protocol are pre-
sented in Fig. 1. The assessments are performed at the
Laboratory of Biomechanics of Human Movement and
Posture (LaBiMPH) at the Physical Therapy, Speech and
Occupational Therapy department of the School of
Medicine of the University of São Paulo, São Paulo,
Brazil.
Participants and recruitment
This study is currently recruiting patients (study start
date: April 2015)
The eligibility criteria for the volunteer runners are:
– aged between 18 and 55 years old
– at least 1 year of running experience
– a weekly training distance greater than 20 km an
less than 100 km as their main physical activity
– within 2 months prior to baseline assessment, lack
of any lower limb musculoskeletal injury or pain
that might lead to stopping running practice
– no prior experience within the last year of isolated
foot and ankle strength training
– not receiving any physical therapy intervention
– no history of using minimalist shoes for running
practice
– no prior experience of barefoot running
Runners are not selected if they have other neuro-
logical or orthopedic impairments (such as congenital
foot malformations, stroke, cerebral palsy, poliomyelitis,
rheumatoid arthritis, prosthesis or moderate or severe
osteoarthritis), major vascular complications (venous or
arterial ulcers), diabetes mellitus, sequelae from poorly
healed fractures or prior lower-limb surgeries.
These runners may use the running technique of
fore-, mid- or rear-foot ground contact, which will be
classified by the strike index, according to Cavanagh
and Lafortune [30].
One hundred and eleven (111) runners will be re-
cruited by radio advertisements, print media and run-
ning association groups at their site of practice around
the city of São Paulo. The potential subjects will be
interviewed by telephone and, when selected, assessed in
the laboratory to confirm all the eligibility criteria. This
first laboratory assessment represents the baseline con-
dition (blind assessment).
The runners allocated to the IG will be treated during
their locally supervised session at the Physical Therapy
Department in an ambulatory setting that assists all the
physical therapy treatments of the Department, providing
a reliable therapeutic environment for the intervention.
Randomization, allocation and blinding
The randomization schedule was prepared using Clinstat
software [31] by an independent researcher (Researcher
1) who was not aware of the numeric code for the CG
and IG groups. A numeric block randomization se-
quence will be kept in opaque envelopes.
After the runners’ agreement to participate and assign-
ment in the research, the allocation into the groups will
be made by another independent researcher (Researcher
2), who also will be unaware of the codes. Only the
physiotherapist (Researcher 3) responsible for the locally
supervised training knows who is receiving the interven-
tion. Researcher 3 will also be responsible for the remote
monitoring of the training by web software [29] and tele-
phone. One physiotherapist (Researcher 4), who will also
be blind to the treatment allocation, will be responsible
for all clinical, functional and biomechanical assess-
ments. Both physiotherapists (researchers 3 and 4) will
be blind to the block size used in the randomization
procedure.
To guarantee the blindness of researcher 4, before
each evaluation, runners will be instructed not to reveal
whether they are in the CG or IG; their questions should
be asked only to the physiotherapist in charge of web
software [29] and local training (Researcher 3).
The trial statistician will also be blind to treatment al-
location until the main treatment analysis has been
completed.
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 4 of 11
Treatment arms
The CG runners will receive a 5-min placebo routine of
warm-up and muscle-stretching exercises to be per-
formed immediately before every running practice dur-
ing their 8-week study (Additional file 1: Table S3).
The IG runners will receive a therapeutic foot-ankle
exercise protocol for strengthening and improving func-
tionality under the supervision of a physiotherapist
(Researcher 4) once a week for 8 weeks, and a series of
foot-ankle exercises to be performed under remote
supervision through web software [29] three times a
week for the full 1-year length of the study (1 year). Both
locally (Additional file 1: Table S1) and remotely super-
vised therapeutic routines (Additional file 1: Table S2)
will take from 20 to 30 min. In particular, the remotely
supervised practice will be preferentially performed at
Fig. 1 Flow chart of the study’s design
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 5 of 11
home; the web software includes written descriptions,
photos and videos of each exercise.
Each week, IG runners will be requested to evaluate
the subjective effort of each exercise’s performance using
a score of 0 to 10 either with the web software [29] or to
the physiotherapist during locally supervised practice. If
the effort score ranges from 0 to 5 and the runner’s per-
formance of each exercise is found adequate during the
supervised session by the physiotherapist, the exercises
will increase in difficulty according to the progression
chart in Additional file 1: Table S1 and Table S2. If the
effort score ranges from 6 to 7, the exercise will not in-
crease in difficulty and no progression would be done on
that exercise. Thus, the runner remains in the same ex-
ercise progression until he/she scores 0 to 5 in each par-
ticular exercise. Finally, if an IG runner reports a score
from 8 to 10, the exercise will decrease in difficulty, if
possible, until the subject is able to perform it without
pain or discomfort.
Assessments
A physiotherapist (Researcher 3) who is blind to group
allocation will perform all assessments. Each assessment
will consist of taking a clinical history of personal details,
anthropometry, running practice details (years of prac-
tice, weekly frequency and volume, usual shoe and train-
ing surface, number of races and whether the runner
trains with a running coach), previous orthopedic sur-
gery, other physical activity practiced regularly (previous
to running practice or simultaneously with running) and
an injury history concerning the most important risk
factors previously published [3, 32, 33].
A foot-health status questionnaire [34] will be used to
characterize foot health and functionality. We will use a
Brazilian-Portuguese version (FHSQ-BR) translated and
validated by Ferreira et al. [35]. This instrument is di-
vided into three sections. Section I evaluates foot health
in four domains: foot pain, foot function, footwear and
general foot health. Section II evaluates general health in
four domains: general health, physical activity, social
capacity and vigour. Sections I and II are composed of
questions with answer options presented in affirmative
sentences and corresponding numbers. Section III col-
lects general demographic data of the individuals [36].
We will not use the scores from Section III. Each do-
main scores from 0 to 100 points, where 100 is the best
condition and 0 the worst.
We will access variations in foot posture of the run-
ners using the Foot Posture Index (FPI) [36]. The FPI is
a six component measures that allows multiple segment
evaluation of foot posture on a static measurement and
requires that subjects stand in their relaxed stance pos-
ition looking straight ahead while the assessment is in
process. The assessment consists on the (1) palpation of
the talar head, (2) observation of supra and infra malleo-
lar curvature, (3) observation of the calcaneal frontal
plane position, (4) observation of the bulging in the re-
gion of the talo-navicular joint, (5) observation of the
height and congruence of the medial longitudinal arch
and (6) presence of abduction or adduction of the fore-
foot. Scores reaching from -12 to +12 and normative
values are presented on the literature.
Subjects will then be assessed for intrinsic foot muscles
strength, lower-limb running kinematics and kinetics, and
dynamic foot-arch strain. The feet of 30 % of the partici-
pants in each group (41 participants) will be imaged by
magnetic resonance imaging (MRI) to assess trophism
and strength of the foot intrinsic muscles; this will be
scheduled for the same week of each subject’s baseline
measurements.
After baseline assessment, all subjects will be sched-
uled for two follow-ups assessments, one at 8 weeks and
the other at 16 weeks. They will maintain contact with
the Researcher 3 through the follow-up period by the
web software [29], e-mail and telephone.
Running-related injuries
Running-related injuries will be assessed initially at the
baseline and will be assessed continually throughout the
study by the web software [29]. The definition of
running-related injury was set according to the study of
Macera et al. [4]. They stated that any musculoskeletal
pain or injury that was caused by running practice and
that induces changes in the form, duration intensity or
frequency of training for at least 1 week will be consid-
ered a running-related injury. Only lower-limb injuries
will be accounted during the 12-month period after the
baseline assessment; both the incidence and time of oc-
currence of the first injury will be analyzed.
If any subject presents a new injury during his or her
participation in the study, the injury will be accounted
for and the intervention or placebo intervention will be
discontinued, even though all subjects will still keep be-
ing followed for the completion of the study.
Isometric intrinsic foot muscles strength
Strength of the foot’s intrinsic muscles will be assessed
in trials using a pressure platform (EMED: Novel,
Germany) on which the subjects will place their domin-
ant foot while standing with knees extended. They will
push down as hard as possible using only their hallux
and toes, particularly the metatarsophalangeal joints and
not the hallux interphalangeal joint. A physiotherapist
will determine whether the subject lifted the heel, and
inspect fluctuations in the line of gravity and trunk pos-
ture during each trial. If any changes are observed in the
line of gravity or positioning of the heel or trunk, the
trial will be excluded. Three trials will be completed on
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 6 of 11
each foot (left and right) according to Mickle et al.
(2006) [37]. Maximum force will be normalized by body
weight and analyzed for hallux and toes areas separately.
Foot muscle trophism and strength
One indirect method of measuring foot strength is
through MRI, which, combined with other techniques,
offers good reliability and a way to follow changes in
muscular volume [38]. In addition, MRI can facilitate
understanding the etiology of running-related injuries
and rehabilitation of the foot-ankle complex [39].
The MRI of the foot will be performed with a 1.5 T sys-
tem. Foot images will be acquired by the same technician
using a coil of four channels positioned in the magnetic
centre. Participants will be placed in supine position with
the ankle at 45° of plantar flexion inside the coil. Images
will be acquired in the frontal, sagittal and transverse
planes to confirm the position of the feet, and the subject
will be repositioned if necessary. T1-weighted images of
the entire foot length will be acquired perpendicular to
the plantar aspect of the foot using a spin-echo sequence
(repetition time = 500 ms, echo time = 16 ms, averages = 3,
slice thickness = 4 mm, gap between slices = 0 mm, field of
view = 120 × 120 mm, flip angle = 90°, matrix = 512 × 512)
[39]. The set of images will cover the distance between the
most proximal and most distal images in which every in-
trinsic foot muscle is visible.
To assess changes in the cross-sectional area (CSA)
and volume of the intrinsic foot muscles, 30 % of the
subjects from each group will have MRI of the foot at
three times: baseline, 8 weeks and 16 weeks.
The CSA will be measured by ImageJ planimeter soft-
ware [40]. Following, Miller et al. [14] for each muscle at
each slice and muscle volume will be calculated by
multiplying the CSA of all slices for a muscle by their
linear distance (4 mm) and adding these volumes.
Walking and running biomechanics
To ensure maximum reliability, all biomechanical testing
sessions will be completed by the same researcher.
Gait and running kinematics will be acquired using
three-dimensional displacements of passive reflective
markers (10 mm in diameter) tracked by nine infrared
cameras at 100 Hz (OptiTrack FLEX: V100, Natural
Point, Corvallis, OR, USA) [41, 42]. Some 14 markers
will be placed on the right subject’s foot according to
Leardini’s protocol [43]. Extra markers will be placed at
the medial knee joint line, lateral knee joint line and bi-
laterally at the iliac spine antero-superior, superior as-
pect of the greater trochanter, and sacrum. These
markers will be used to determine relative joint centres
of rotation for the longitudinal axis of the foot, ankle
and knee. The extra markers from the medial aspect of
the knee joint line will be removed during the dynamic
trial. In addition, three non-collinear reflective markers
will be fixed at two technique clusters. One of the clus-
ters will be placed in the lateral thigh and the other over
the shank.
The laboratory coordinate system will be established at
one corner of the force plate and all initial calculations
will be based on this coordinate system. Each lower-limb
segment (shank and thigh), will be modelled based on
surface markers as a rigid body with a local coordinate
system that coincides with the anatomical axes. Transla-
tions and rotations of each segment will be reported
relative to the neutral positions defined during the initial
static standing trial. All joints will be considered to be
spherical (i.e., with three rotational degrees of freedom).
The foot will be modeled according to Leardini et al.
[43]. That is, the calcaneus, mid-foot and metatarsus are
considered rigid bodies and the longitudinal axis of the
first, second and fifth metatarsal bones and proximal
phalanx of the hallux will be tracked independently.
Ground reaction forces will be acquired by a force
plate (AMTI OR-6-1000, Watertown, MA, USA) with a
sampling frequency of 1 kHz embedded in the centre of
the walkway. Force and kinematic data acquisition will
be synchronized and sampled by an A/D card (AMTI,
DT 3002, 12 bits).
The subjects will go through a habituation period before
the data acquisition to establish confidence and comfort
in the laboratory environment, and to ensure appropriate
movement velocity. To assess lower-extremity running
mechanics, subjects will perform 10 valid over-ground
walking trials and 10 valid over-ground running trials at a
constant velocity (9.5 km/h to 10.5 km/s); these will be
monitored by two photoelectrical sensors (Speed Test Fit
Model, Nova Odessa, Brazil).
The automatic digitizing process, 3D reconstruction of
the markers’ positions and filtering of kinematic data will
be performed using AMASS software (C-motion, Kingston,
ON, Canada). Kinematic data will be processed using a
zero-lag second-order low-pass filter with cutoff frequen-
cies of 6Hz for walking and 12 Hz for running. Ground
reaction force data will be processed using a zero-lag low-
pass Butterworth fourth-order filter with cutoff frequencies
of 50Hz for walking and 200 Hz for running.
A bottom-up inverse dynamics method will be used to
calculate the net moments in the sagittal and frontal planes
of the ankle and knee joints using Visual3D software
(C-motion, Kingston, ON, Canada). The human body will
be
modeled
by
three
linked
segments
(foot,
shank
and thigh) and the inertial properties will be based on
Dempster’s standard regression equations. The moment of
inertia and location of center of mass will be computed
assuming the thigh and shank segments as cylinders.
Calculation of all variables will be performed using a
custom-written MATLAB function (MathWorks, Natick,
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 7 of 11
MA, USA). Data of only one lower limb (randomly
chosen) per subject will be analyzed and compared.
The following ankle kinematic variables will be analysed:
maximum dorsiflexion at foot contact, maximum plantar-
flexion, maximum dorsiflexion at the toe-off and dorsiflex-
ion range of motion (ROM) in the sagittal plane during the
stance phase. The knee kinematic variables are: maximum
flexion at foot contact, maximum extension, maximum
flexion in the stance phase, ROM on sagittal plane, max-
imum abduction and adduction in the stance phase. The
foot kinematic variables are: elevation/drop of the longitu-
dinal arch angle and of the first, second and fifth metatarsal
bones; rearfoot to forefoot rotation; transverse plane angle
between first and second metatarsal bones and between
second and fifth metatarsal bones; and maximum inversion
and eversion of the calcaneus (frontal plane).
The ankle and knee kinetic variables to be analysed are
net ankle and knee moments normalized by body weight
times height and power normalized by body weight in the
sagittal plane. The ground reaction force variables will be
normalized by body weight and are as followings: first peak
force (body weight – BW), second peak (BW), loading rate
80 [N/ms], defined as the force rate between 20 and 80 %
of the contact of the foot with the ground during the first
peak; loading rate 100 [N/ms], as determined by the force
rate between 0 and 100 % of the first peak and push-off rate
[N/ms], as defined as the rate of the second peak force, be-
tween the minimal values until the second peak.
Dynamic longitudinal foot arch strain
The dynamic longitudinal foot arch strain will be measured
according to Liebermann et al. [44]. The measurement in-
volves navicular height (NH), which is the minimum distance
from the navicular tuberosity relative to the line formed by
the first metatarsal head and the medial process of the calca-
neus. These three landmarks form a plane and NH is inde-
pendent of rear-foot inversion or eversion. Arch strain can
also be quantified by fitting a parabola to markers (with the
navicular head as the vertex) and then measuring the average
curvature at 100 points evenly spaced along the curve.
Outcome measurements
The primary outcome measurement will be the inci-
dence of running-related injuries in the lower limbs
accounted at the end of 12 months of study.
The secondary outcomes will be: 1) the time of the
occurrence of the first injury along the study period (time
to event); 2) foot health and functionality (change from
baseline); 3) foot, ankle and knee kinematics, ankle and
knee joint moments, and knee and ankle power during
walking and running (change from baseline); 4) strength
of the intrinsic foot muscles (change from baseline);
5) foot muscle trophism (change from baseline); and
6) dynamic foot arch strain (change from baseline).
Interventions
Runners allocated to the IG will receive a foot-ankle thera-
peutic exercise protocol for strengthening and improving
functionality. Part of the exercise protocol (12 exercises) is
to be performed once a week under the supervision of a
physiotherapist for 8 weeks (Additional file 1: Table S1).
And a series of eight foot-ankle exercises is also to be
performed three times a week remotely supervised by
web software [29] (Additional file 1: Table S2) for the full
1-year completion time of the study. Each session,
whether supervised locally or remotely, lasts 20 to 30 min.
The therapeutic exercise protocol is described in details in
Additional file: 1 Table S1 and S2.
Gradual and progressive difficulty will be offered to
the runner, respecting any limitation due to pain, fatigue
and/or decrease in performance during execution. The
runners in the IG will access the web software [29] daily,
entering their data regarding performance of the foot
exercise training and ranking their level of difficulty in
each exercise from 0 to 10.
During the locally supervised sessions, the physiotherapist
will focus on proper alignment of the foot-ankle segments,
especially if the runner has difficulty in maintaining it, in a
way that allows no movement compensations.
Runners allocated to the CG will receive a 5-min
placebo warm-up and muscle stretching exercise routine
(Additional file 1: Table S3) that they are to perform for
8 weeks immediately before each running practice. This
placebo training can also be assessed and followed
through the web software [29]. The stretching exercises
are described in detail in Additional file: 1 Table S3. We
hypothesized that a warm-up combined with muscle
stretching exercises would not have any effect on foot
muscular strength and functionality, lower extremity
biomechanics or injury prevention.
Both groups will access the web software [29] daily,
entering their running practice data (daily training
duration and volume) and information concerning the
occurrence of any injury event.
The discontinuation criteria for the exercises during
any session includes cramps, moderate to intense pain,
fatigue or any other condition that exposes the runner
to any discomfort.
The discontinuation criteria for the training includes an
occurrence of a running-related injury in the lower limbs.
If any subject fails to access the web software [29]
for three consecutive weeks without explanation, or
fails to attend the locally supervised training three
consecutive times, that subject will be terminated
from the study.
To improve adherence, several actions will be per-
formed by the researchers in the web software [29]. Data
regarding the subjects running practice, such as training
volume, time of practice and occurrence of injuries, will
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 8 of 11
be reported to the web software, which will summarize
it and make it viewable in the users’ area. In addition,
for the duration of the study, runners' responses in the
web software concerning their foot-ankle exercise prac-
tice and running training will be stored and be accessible
to the researchers and subjects at any time. If any sub-
ject fails to log in to the web software for more than five
consecutive days, an e-mail will be automatically be sent,
asking the subject to log in to his or her account and re-
port data on the training (or lack of it) for the past week.
The physiotherapist responsible for the
therapeutic
protocol will make phone contact with subjects who fail
to attend to any of the weekly locally supervised ses-
sions. They will also make phone contact with subjects
who do not respond to e-mail reminders from the web
software. Subjects will also be contacted by personal
phone calls if data they reported on the web software is
found to be inconsistent [45].
After the period of intervention and after 12 weeks of
follow up all runners will be questioned about their sat-
isfaction to the training protocol with one question (Did
you enjoy doing the exercises?) with three answer possi-
bilities (No; A Little; A lot). To avoid evaluation bias,
runners will answer this question secretly through an
online-unidentified form sent to their e-mail. Runners
will be informed about the anonymity and this form will
only be accessed after completion of the study.
For the duration of the trial, subjects will be advised not
to engage in any new physical activity or preventive train-
ing protocols for the foot and ankle. If any subject cannot
avoid such behavior, he or she must report this situation
during web software [29] access. Concomitant care, such
as physical therapy, acupuncture or other conventional
medical care, will not be permitted except for runners
who are injured during the study. At the end of 12 months,
CG participants that are interested will receive access to
the software for the foot exercise protocol.
Sample size and statistical analysis
The sample size calculation was made using an effect size
of 0.28 (proportion), considering the categorical primary
outcome variable, which is the incidence of running-
related lower-limb injuries [33]. A sample size of 101 run-
ners is needed to provide 80 % power to detect a moderate
effect difference between the highest and lowest group
injury incidence medians, assuming an alpha of 0.05 and a
χ2 (chi-squared test) statistical design – contingency tables
(df = 1) [46]. Assuming a 10 % dropout rate during the
study, a sample size of 111 runners is needed.
The statistical analysis will be based on intention-to-
treat analysis, and mixed general linear models of analysis
of variance for repeated measure will be used to detect
treatment-time interactions (α = 5 %). The outcome mea-
sures will be compared at baseline, 2, 4 and 12 months.
Effect sizes (Cohen´s d coefficient) will also be provided
between baseline and 2 months and between 2 months
and follow-up (4 and 12 months), if the intervention
shows any treatment effect. The missing data will be
treated by imputation methods depending on the type of
the missing data we will face: missing completely at ran-
dom, missing at random, or missing not at random [47].
Discussion
This clinical trial will provide important data on foot-
training effectiveness, its influence on the incidence of
injuries and its efficacy on strengthening the muscles of the
foot-ankle complex. It will also facilitate the identification
of risk factors and biomechanical mechanisms involved in
injury processes and prevention. We also intend to contrib-
ute new evidence that could be used as a guide for further
studies on biomechanical changes in dynamic tasks result-
ing from the strengthening of the foot-ankle complex.
The few existing clinical trials that have proposed exercise
protocols to reduce the incidence of runners’ injuries have
not included the incidence of injury as a primary outcome.
They also have had short follow-up periods and usually
failed to follow the subjects’ adherence to the program and
the correctness of exercise performance throughout the
study [13, 17, 19, 20]. In contrast, this trial has the incidence
of running-related injuries as a primary outcome, will have a
long period of follow-up (12 months), proposes an interven-
tion training protocol with several exercises that are easy to
perform with short durations for each session (20–30 min)
and does not require subjects to be continuously supervised
by a health professional. In addition, it utilizes open-access
web software [29] that will support adherence control.
We understand that the number of MRIs that we are
performing (on 30 % of the subjects) is limited and might
prevent a broad conclusion about changes in intrinsic foot
muscle cross-sectional area (CSA) and volume.
Running-related injuries in this population cause inter-
ruptions and abandonment of physical activity. They also
could lead to the development of chronic injury that
would prevent the practice of other sports and hence
frustrate the individual’s pursuit of a healthy lifestyle.
Runners are constantly looking for ways to remain free
from injury and the information they receive from coa-
ches or media is often conflicting and varied [48]. Our
protocol has the potential to change the course of this
vicious cycle experienced by long-distance runners.
If our hypothesis that such an exercise protocol reduces
the incidence of running-related injuries to long-distance
runners is confirmed, it could be easily incorporated into
their warm-up routine prior to running practice.
Ethics approval and consent to participate
This trial was approved by the Ethics Committee of the
School of Medicine of the University of São Paulo (Protocol
Matias et al. BMC Musculoskeletal Disorders  (2016) 17:160 
Page 9 of 11
number n°031/15). Additionally, this trial is registered in
ClinicalTrials.gov (a service of U.S. National Institutes of
Health) Identifier NCT02306148 (November 28, 2014)
under the name “Effects of Foot Strengthening on the Preva-
lence of Injuries in Long Distance Runners”. All runners will
be asked for written informed consent according to the
standard forms and the researcher 4 will obtain them.
Consent to publish
Written informed consent for publication of all images
was obtained from the models.
Availability of data and materials
All personal data from potential or enrolled runners will be
maintained confidential before, during and after the trial by
encoding participant’s name. All data access and storage are
in keeping with National Health and Medical Research
Council guidelines, as approved. All files will be available
from the database published at figshare.com. All important
protocol amendments will be reported to investigators, re-
view boards and trial registration by the Researcher 3.
Additional file
Additional file 1: Table S1. Exercises included in the supervised
sessions by a physiotherapist. Table S2. Exercises included in the
remotely supervised sessions in the web software. Table S3. Warm up
and stretching exercises - Control group. (DOCX 2425 kb)
Abbreviations
CG: Control group; CSA: Cross-sectional area; FHSQ-BR: Foot-health status
questionnaire - Brazilian-Portuguese version; FPI: Foot Posture Index;
IG: Intervention group; MRI: Magnetic resonance imaging; NH: Navicular height.
Competing interests
The authors affirm that this study has not received any funding/assistance
from a commercial organization which may lead to a conflict of interests.
Authors’ contributions
All authors have made substantial contributions to all three of sections (1),
(2) and (3): (1) The conception and design of the study, or acquisition of
data, or analysis and interpretation of data (2) drafting the article or revising
it critically for important intellectual content (3) final approval of the version
to be submitted. And in the protocol the following roles will be played by
the authors: UTT is responsible for the study design, intervention,
interpretation of the data, writing the report and submission of the
manuscript. ABM is responsible for the study design, data collection,
management, analysis, and interpretation, writing the report and submission
of the manuscript. ICNS is responsible for the study design, interpretation of
the data, writing the report and submission of the manuscript.
Acknowledgements
The authors are grateful to the State of São Paulo Research Foundation (FAPESP
2014/27311-9; 2015/14810-0), and the Agency Coordination of Improvement of
Higher Education Personnel (CAPES) for the funding granted to this study. The
funders do not have any role in the study and do not have any authority over
any study activity or in the decision to submit the report for publication. The
authors acknowledge Oliveira CC, Soares L, Amorim LG and Vilas Boas C for the
help with the web-software’s construction.
Author details
1Department of Physical Therapy, Speech, and Occupational Therapy, School
of Medicine, University of São Paulo, Rua Cipotânea, 51 - Cidade Universitária,
05360-160 São Paulo, São Paulo, Brazil. 2Federal University of ABC, Biomedical
Engineering, São Bernardo, São Paulo, Brazil.
Received: 2 March 2016 Accepted: 7 April 2016
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Protocol for evaluating the effects of a therapeutic foot exercise program on injury incidence, foot functionality and biomechanics in long-distance runners: a randomized controlled trial.
Matias, Alessandra B,Taddei, Ulisses T,Duarte, Marcos,Sacco, Isabel C N