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Scand J Med Sci Sports. 2020;30:1360–1368.
wileyonlinelibrary.com/journal/sms
1 | 
INTRODUCTION
The medial longitudinal arch is a unique structure in the 
human foot. During weight-bearing exercises, the foot arch 
lowers while being stretched out and then recoils as the 
load is removed. Such a spring-like property of the foot 
arch helps to attenuate impact forces and store/release elas-
tic strain energy leading to energy saving during running.1 
It is known, however, that long-distance running (LDR) 
imposes repetitive mechanical stress on the foot, thereby 
inducing transient lowering of the foot arch.2,3 As the foot 
arch is temporarily collapsed, its force attenuation capacity 
Received: 14 December 2019 | 
Revised: 1 April 2020 | 
Accepted: 15 April 2020
DOI: 10.1111/sms.13690  
O R I G I N A L  A R T I C L E
Acute effects of long-distance running on mechanical and 
morphological properties of the human plantar fascia
Hiroto Shiotani1,2
 |   Tomohiro Mizokuchi3 |   Ryo Yamashita3 |   Munekazu Naito4,5
 |   
Yasuo Kawakami5,6
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original 
work is properly cited.
© 2020 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd
1Graduate School of Sport Sciences, 
Waseda University, Saitama, Japan
2Research Fellow of Japan Society for the 
Promotion of Science, Tokyo, Japan
3School of Sport Sciences, Waseda 
University, Saitama, Japan
4Department of Anatomy, Aichi Medical 
University, Aichi, Japan
5Human Performance Laboratory, 
Organization for University Research 
Initiative, Waseda University, Tokyo, Japan
6Faculty of Sport Sciences, Waseda 
University, Saitama, Japan
Correspondence
Yasuo Kawakami, Faculty of Sport 
Sciences, Waseda University, 2-579-15 
Mikajima, Tokorozawa, Saitama 359-1192, 
Japan.
Email: ykawa@waseda.jp
Funding information
Japan Society for the Promotion of Science, 
Grant/Award Number: 16H01870 and 
19J14912 
Long-distance running (LDR) can induce transient lowering of the foot arch, which 
may be associated with mechanical fatigue of the plantar fascia (PF). However, this 
has not been experimentally tested in vivo. The purpose of this study was to test 
our hypothesis that LDR induces transient and site-specific changes in PF stiffness 
and morphology and that those changes are related to the lowering of the foot arch. 
Ten male recreational long-distance runners and 10 untrained men were requested 
to run overground for 10 km. Before and after running, shear wave velocity (SWV: 
an index of soft tissue stiffness) and thickness of PF at three different sites from its 
proximal to distal end were measured using supersonic shear imaging and B-mode 
ultrasonography. Foot dimensions including the navicular height were measured 
using a three-dimensional foot scanner. SWV at the proximal site of PF and navicu-
lar height was significantly decreased in both groups after running, with a higher 
degree in untrained men (−21.9% and −14.1%, respectively) than in runners (−4.0% 
and −6.3%, respectively). The relative change (%Δ) in SWV was positively cor-
related with %Δnavicular height in both groups (r = .69 and r = .65, respectively). 
Multiple regression analysis revealed that %ΔSWV at the proximal site solely ex-
plained 72.7% of the total variance in %Δnavicular height. It is concluded that LDR 
induces transient and site-specific decreases in PF stiffness. These results suggest 
that the majority of running-induced lowering of the foot arch is attributable to the 
reduction of PF stiffness at the proximal site.
K E Y W O R D S
elasticity, mechanical fatigue, medial longitudinal arch of the foot, plantar aponeurosis, stiffness, 
supersonic shear imaging, thickness, ultrasound shear wave elastography
   | 
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SHIOTANI eT Al.
is compromised. A collapsed foot arch (eg, pes planus) is 
known to increase the risk of injury around the lower limb 
and foot.4,5
Previous work indicates that the foot arch elasticity is pri-
marily attributed to the plantar fascia (PF).1,6,7 PF behaves 
visco-elastically under tension and contributes to the elas-
tic recoil of the foot arch.1,8-11 During each foot contact of 
running, PF repetitively experiences tension as high as 0.6-
3.7 times the body weight, with its longitudinal strain up to 
6%.12-15 Simulation studies have shown that the tension and 
peak stress along PF concentrate at its proximal sites.16-18 
Accumulation of such repetitive and site-specific stress on PF 
can induce mechanical fatigue (ie, reduction of stiffness and 
increased strain upon loading).19-21 This can be a major factor 
for the lowering of the foot arch during LDR. This potential 
mechanism should be experimentally tested, but no study has 
ever attempted to quantitatively evaluate the running-induced 
mechanical fatigue of PF in vivo and relate it to the lowering 
of the foot arch.
Long-distance runners, regardless of their performance 
level, are known to be the most prevalent and vulnerable 
population to plantar fasciitis.5,22,23 On the other hand, the 
plasticity of connective tissues’ mechanical and morpho-
logical properties allows them to adapt to chronic mechan-
ical loading (eg, increases in stiffness and cross-sectional 
area).24,25 Therefore, it is possible that well-experienced 
long-distance runners possess PF and a foot arch that are 
adapted to LDR (smaller changes in PF properties and 
arch deformation) as compared to untrained individuals. 
Available knowledge is limited for this issue. The purpose 
of the present study was to investigate the acute effects of 
LDR on the mechanical and morphological properties of PF 
and the foot arch in untrained individuals and long-distance 
runners. The hypotheses were (a) LDR induces transient 
and site-specific changes in PF stiffness and morphology, 
(b) those changes in PF are related to the indices of lowering 
of the foot arch, and (c) LDR shows smaller changes in PF 
characteristics and foot dimensions after running in runners 
than in untrained individuals.
2 | 
MATERIALS AND METHODS
2.1 | Participants
Twenty healthy young men (10 recreational long-distance 
runners and 10 untrained individuals; Table 1) participated in 
this study. All participants had no lower extremity injury in 
the past 12 months or subjective symptom that would impede 
running at the time of measurement. The runners had kept 
habitual running for at least 10 km/wk for the year, and their 
running experiences ranged between 9 and 16 years. The un-
trained participants were either sedentary or lightly active, 
and none of them had been involved in any structured LDR 
program or continuous sports participation at least 12 months 
before the measurement. This study was approved by the 
Institutional Human Research Ethics Committee and was 
carried out in accordance with the Declaration of Helsinki. 
Written informed consent was obtained from all participants 
before data collection.
2.2 | Protocol
Prior to visiting the laboratory, participants were asked not to 
perform any strenuous exercises for at least 24 hours before 
the measurements. A test-retest protocol was used to exam-
ine the acute effects of LDR. Participants were requested to 
run for 10 km on a 700 m outdoor asphalt-surface circular 
path adjacent to the laboratory. The protocol was assumed 
to be identical regarding the mechanical loading for the two 
groups given that they possess comparable stature (Table 1), 
and the condition was standardized with the running velocity 
set at 10 km/h. Lap time was recorded, and running veloc-
ity was adjusted by oral instruction. Participants wore their 
own sports clothes and running shoes during running, but no 
one used unsuitable shoes that could confound the results (eg, 
the minimalist, high cushion or high motion control shoes). 
The foot strike pattern of participants was visually confirmed 
throughout the running task. All participants were able to 
complete this 10-km running task without resting or walking. 
The average completion time was 0:59:57 (0:59:04-1:00:57). 
Before (Pre), immediately after (Post), and 30 and 60 min-
utes after the termination of running, participants underwent 
the measurement to examine PF stiffness, thickness, and foot 
dimensions of their right feet. Care was taken to ensure that 
participants were in the same posture during pre- and post-
running measurements.
TABLE 1 
Physical characteristics of participants
Variable
Runners
Untrained men
P value
n
10
10
-
Age (y)
22.0 ± 0.7
22.5 ± 1.4
.31
Height (m)
1.68 ± 0.04
1.70 ± 0.05
.39
Body mass (kg)
55.5 ± 4.2
58.4 ± 5.6
.06
BMI (kg/m2)
19.6 ± 1.2
20.3 ± 1.7
.11
Running 
experience (y)
11.0 ± 2.2
-
-
Running distance 
(km/wk)
43.7 ± 35.4
-
-
RFS: FFS (n)
7:3
10:0
.06
Note: Data are shown as mean ± SD.
Abbreviations: BMI, body mass index; FFS, forefoot strikers; RFS, rearfoot 
strikers.
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SHIOTANI eT Al.
2.3 | Ultrasound measurements
To measure mechanical and morphological properties of PF, 
supersonic shear imaging (SSI) and B-mode ultrasonography 
were used. SSI is a valid and reliable technique to evaluate 
stiffness and morphology of skeletal muscles, tendons, and 
fasciae in vivo.26-28 SSI uses acoustic push pulses that propa-
gate in the soft tissues and measures their velocity (ie, shear 
wave velocity: SWV) as an index of stiffness.29,30 We re-
cently developed a technique using SSI to measure localized 
SWV values and thickness of PF with high repeatability.31
Details of measurement and data processing are reported 
elsewhere31; but briefly, B-mode images and shear wave data 
were obtained using an Aixplorer ultrasound scanner (version 
6.4; Supersonic Imagine) with a linear array transducer (SL 
15-4; Supersonic Imagine). Participants were requested to 
rest in a supine position on the examination bed with the knee 
fully extended, and their ankle and toe digits were secured to 
a custom-made fixture at the neutral position (Figure 1). PF 
was scanned in the longitudinal direction at the proximal (in 
the proximity to the calcaneus), middle (the level of navicu-
lar tuberosity), and distal (proximity to the second metatar-
sal head) sites. The locations of the transducer were marked 
on the skin surface using a waterproof marker for identical 
measurement locations. For each measurement site, B-mode 
images and shear wave data were recorded for 7 seconds with 
a system operating at 12 Hz (ie, the default sampling rate 
of SSI measurement of the current version of the ultrasound 
scanner). After the data collection, three images separated by 
12 frames from the middle of the 7 seconds recording were 
picked up and used for further analysis.
SWV was obtained as the mean value within the region 
of interest (ROI) which was manually traced over the fascial 
boundaries of PF using a measurement tool included in the 
Aixplorer software (Q-boxTM Trace). Mean ROI size at the 
proximal, middle, and distal sites were approximately 0.34, 
0.22, and 0.17 cm2, respectively. Care was taken to exclude 
any rejection (ie, the area with pixels having no color) within 
ROI to avoid underestimation of SWV (33 of the 720 im-
ages used in this study had rejection areas of approximately 
0.01 cm2). To assess PF morphology, the distance between 
the superficial and deep fascial boundaries was measured 
to determine thickness using a measurement tool (distance). 
Three images were analyzed for SWV and thickness at each 
measurement site of PF; then, the three values were averaged 
to obtain the representative value for each site.
2.4 | Measurements of foot dimensions
A three-dimensional foot scanner (JMS-2100CU; Dream GP) 
was used to obtain foot dimensions. The scanning and analy-
sis procedure were based on previous studies which reported 
transient changes in the foot shapes after LDR using the same 
system.2,3 The foot was scanned both in a sitting and standing 
positions. A laser scanner moved around the foot in an oval 
trajectory, measuring the foot dimensions and the anatomical 
marker positions based on laser line triangulation with high 
accuracy.2,3 After the scanning, foot length, dorsal height, 
and navicular height were obtained. The arch height ratio 
was calculated as the navicular height normalized to the foot 
length. Navicular drop was calculated as the difference in the 
navicular height between sitting and standing positions. Foot 
dimensions in the standing position are reported as the repre-
sentative values unless otherwise noted.
2.5 | Statistical analysis
An unpaired t test was performed to test the difference 
in physical characteristics between groups. The fractions 
of rearfoot (RFS) and forefoot strikers (FFS) within each 
FIGURE 1 
Experimental setup and representative ultrasound B-mode and shear wave images of the plantar fascia (PF) at the proximal (P), 
middle (M), and distal (D) sites. ROI, region of interest
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SHIOTANI eT Al.
group were compared with a Pearson chi-squared test. 
Changes in SWV, thickness, and foot dimensions were 
compared by a two-way (4 time points x 2 groups) re-
peated measures analysis of variance (ANOVA). If signifi-
cant main effects and/or interactions were found, Dunnett's 
test or an unpaired t test was performed as a post-hoc test, 
where appropriate. If there was no significant main effect 
or interactions for ANOVA or significant difference for a 
post-hoc test, a post-hoc power analysis (G*Power v3.1; 
Heinrich Heine-Universität) was performed to test our 
sample size was sufficient for 80% statistical power at a 
significance level of α = .05.
To examine the difference between groups in the degree 
of running-induced changes in SWV, thickness, and foot di-
mensions, relative change (%Δ) from pre- to post-running 
were calculated for these variables and were compared by 
an unpaired t test between groups. As indices of effect size, 
partial η2 (for ANOVA) and Cohen's d (for a post-hoc test) 
were calculated. A post-hoc power analysis estimated that the 
effect size needed for 80% power was d ≥ 0.577. To exam-
ine the relationships of individual %Δnavicular height and 
%Δarch height ratio with %ΔSWV and %Δthickness at each 
measurement site, Pearson product-moment correlation coef-
ficients were calculated. Moreover, to determine predictive 
variables for %Δnavicular height and %Δarch height ratio, 
six independent variables (%ΔSWV and %Δthickness at 
each measurement site) with combining data of both groups 
were entered into a forward stepwise multiple regression 
model with %Δnavicular height and %Δarch height ratio as 
the dependent variables. The criteria used for entering and 
removing the stepwise regression model were F ≤ 0.05 and 
F ≥  0.10, respectively. Statistical significance was set at 
α = .05. Statistical analysis was performed using SPSS soft-
ware (SPSS Statistics 25; IBM).
3 | 
RESULTS
Age, height, body mass, BMI, and fractions of the foot strike 
patterns were not significantly different between runners and 
untrained men (Table 1). Figure 2 shows the changes in SWV 
at each measurement site in runners and untrained men. SWV 
at the proximal site showed a significant time-group interac-
tion (P = .001, η2 = 0.374). In runners, SWV at the proximal 
site significantly decreased at Post (P = .045, d = 1.026), but 
not at 30 or 60 minutes after running (P ≥ .346, d ≤ 0.208). 
In untrained men, SWV at the proximal site significantly 
decreased at Post (P  =  .003, d  =  1.541) and 30  minutes 
(P = .011, d = 1.309), but not at 60 minutes after running 
(P = .101, d = 0.719). %ΔSWV at the proximal site was sig-
nificantly smaller in runners than in untrained men (P < .001, 
d  =  1.912). SWV at the middle site showed a significant 
main effect of time (P = .010, η2 = 0.321), without a main 
effect of group (P = .401, η2 = 0.040), or their interaction 
(P = .165, η2 = 0.266). Dunnett's test with combining data of 
both groups found that SWV at the middle site significantly 
decreased at Post (P = .036, d = 0.643), but not at 30 or 
60 minutes after running (P ≥ .455, d ≤ 0.300).
Figure 3 shows the changes in PF thickness at each mea-
surement site in runners and untrained men. PF thickness at 
the proximal site showed a significant main effect of time 
(P = .012, η2 = 0.344) and group (P = .048, η2 = 0.200), 
without their interaction (P = .072, η2 = 0.121). However, 
Dunnett's test did not find a significant change in PF thick-
ness at the proximal site in runners (P ≥ .196, d ≤ 0.603) or 
untrained men (P ≥ .196, d ≤ 0.603). PF thickness at the mid-
dle site showed a significant main effect of time (P = .015, 
η2  =  0.174), without a main effect of group (P  =  .947, 
η2  <  0.001) or their interaction (P  =  .115, η2  =  0.103). 
However, Dunnett's test with combining data of both groups 
FIGURE 2 
Shear wave velocity of the plantar fascia at the proximal, middle, and distal sites in runners (closed circles) and untrained men 
(opened circles) measured before (Pre), immediately after (Post), and 30 and 60 min after the termination of running. *Significantly different from 
pre (P < .05). †Combining data of both groups show significant difference from pre (P < .05)
1364 |   
SHIOTANI eT Al.
did not find a significant change in PF thickness at the middle 
site (P = .211, d = 0.429). A post-hoc power analysis using 
the parameters of PF thickness revealed that a total of 18 par-
ticipants (nine participants per each group) were required for 
80% statistical power at a significance level of α = .05.
Table 2 shows the changes in foot dimensions of runners 
and untrained men. Navicular height showed a significant 
time-group interaction (P < .001, η2 = 0.342). In runners, 
navicular height significantly decreased at Post (P = .042, 
d  =  1.129), but not at 30 or 60  minutes after running 
(P ≥ .576, d ≤ 0.163). In untrained men, navicular height 
significantly decreased at Post (P  =  .036, d  =  2.029) and 
30 minutes (P = .043, d = 1.506), but not at 60 minutes after 
running (P = .566, d = 0.200). Arch height ratio showed a 
significant time-group interaction (P  <  .001, η2  =  0.329). 
In runners, arch height ratio significantly decreased at Post 
(P = .044, d = 1.050), but not at 30 or 60 minutes after run-
ning (P ≥ .614, d ≤ 0.161). In untrained men, arch height 
ratio significantly decreased at Post (P = .020, d = 3.773) 
and 30 minutes (P = .048, d = 1.364), but not at 60 min-
utes after running (P = .564, d = 0.200). %Δnavicular height 
(P = .002, d = 1.655) and %Δarch height ratio (P = .001, 
FIGURE 3 
Thickness of the plantar fascia at the proximal, middle, and distal sites in runners (closed circles) and untrained men (opened 
circles) measured before (Pre), immediately after (Post), and 30 and 60 min after the termination of running
TABLE 2 
Changes in the foot dimensions in response to long-distance running
Variable
Runners (n = 10)
Untrained men (n = 10)
Pre
Post
30 min
60 min
Pre
Post
30 min
60 min
Foot length (mm)
245.9 ± 8.6
245.7 ± 8.5
244.3 ± 8.2
244.5 ± 7.7
248.3 ± 8.1
248.5 ± 7.8
248.4 ± 7.3
248.2 ± 7.2
Dorsal height 
(mm)
60.8 ± 4.2
59.6 ± 4.1
60.4 ± 3.9
60.0 ± 4.3
61.1 ± 4.0
60.0 ± 4.6
60.8 ± 4.3
60.8 ± 4.1
Navicular height 
(mm)a,b,c 
41.9 ± 6.8
39.4 ± 7.3*,†
40.6 ± 7.4
41.1 ± 7.1
40.9 ± 5.4
35.2 ± 5.6*,†
37.7 ± 5.7*,†
39.8 ± 5.6
Arch height ratio 
(%) a,b,c 
17.1 ± 3.0
16.3 ± 3.1*,†
16.6 ± 3.2
16.8 ± 3.1
16.4 ± 1.9
14.1 ± 2.0*,†
15.2 ± 2.1*,‡
16.0 ± 2.1
Navicular height 
in sitting 
position (mm)
46.9 ± 5.8
45.5 ± 6.7
46.5 ± 5.7
46.0 ± 6.4
45.9 ± 5.7
42.6 ± 5.5
45.0 ± 5.2
45.4 ± 5.3
Navicular drop 
(mm)a 
5.0 ± 2.0
6.1 ± 2.1*,†
5.9 ± 2.8*,‡
5.0 ± 2.1
5.1 ± 1.2
7.4 ± 1.5*,†
7.3 ± 2.3*,‡
5.6 ± 2.3
Note: Data are shown as mean ± SD.
aSignificant main effect of time (P < .05). 
bSignificant main effect of group (P < .05). 
cSignificant time-group interaction (P < .05). 
*Significantly different from pre-running (P < .05). 
†,‡Effect size is interpreted as large (d ≥ 0.8) and medium (0.8 > d ≥ 0.5), respectively. 
   | 
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SHIOTANI eT Al.
d = 1.679) were significantly smaller in runners than in un-
trained men. Navicular drop showed a significant main ef-
fect of time (P < .001, η2 = 0.341), without a main effect of 
group (P = .281, η2 = 0.064) or their interaction (P = .330, 
η2 = 0.061). Dunnett's test with combining data of both groups 
found that navicular drop significantly increased at Post 
(P = .014, d = 0.880) and 30 minutes (P = .025, d = 0.624), 
but not at 60 minutes after running (P = .586, d = 0.742).
%ΔSWV at the proximal site was positively correlated 
with %Δnavicular height and %Δarch height ratio in both 
runners and untrained men (Figure 4). Stepwise multiple re-
gression analysis revealed that %ΔSWV at the proximal site 
was selected as the single predictor of %Δnavicular height 
and %Δarch height ratio explaining 72.7% and 74.4% of the 
variance, respectively.
4 | 
DISCUSSION
The most important finding of the present study was that 
LDR induced transient decreases of both the foot arch and PF 
stiffness in both runners and untrained individuals and that 
the two variables were inter-related. This suggests that me-
chanical fatigue of PF is one of the causes of foot arch flatten-
ing, and in fact, the change in PF stiffness at the proximal site 
solely explained approximately 70% of the total variance in 
the measures of lowering of the foot arch. These results sup-
port the notion that PF provides a primary supporting base 
for the foot arch,1,6,7 and our study further adds the possibility 
that mechanical fatigue of PF, in its proximal part in particu-
lar, is the key factor for lowering of the foot arch. According 
to simulation studies, the proximal site of PF is where the 
mechanical loading is concentrated.16-18 Such site-specific 
stress accumulation during LDR could be the cause of site-
specificity of mechanical fatigue of PF. It may be worthwhile 
also to note that the proximal site of PF is the common site of 
plantar fasciitis.32 Reduction of PF stiffness can lead to an in-
crease in its strain during running. Mechanical overload and 
excessive strain can produce microscopic damage within PF 
which eventually leads to plantar fasciitis,33 and our findings 
are in support of such pathogenesis. Additionally, lowering 
of the foot arch during running would induce greater ever-
sion of the foot. This can be related to a previous finding that 
lower extremity joint kinematics in the frontal plane gradu-
ally changed (ie, greater eversion of the ankle, greater abduc-
tion of the knee, and greater adduction of the hip) throughout 
a 10-km running.34 Since these kinematic features are known 
to be the risk factors for the running-related injuries,5 me-
chanical fatigue of PF and lowering of the foot arch may also 
increase the injury risk of proximal joints.
Theoretically, repetitive mechanical stress can induce 
thinning of PF by mechanical fatigue and/or creep deforma-
tion.19-21 Our results did not show this, which was against 
our hypothesis but it is in line with a previous study on acute 
effects of walking and running on PF thickness.35 A post-hoc 
power analysis revealed that our sample size was sufficient to 
confidently accept or reject our null hypotheses. Our results 
suggest that PF thickness is unsuitable as an indicator of its 
mechanical fatigue.
Runners showed smaller changes in PF stiffness and 
foot arch deformation after LDR than untrained men. This 
suggests adaptability of PF mechanical properties: runners 
may have a more resilient PF to protect against the risk of 
running-related injury, which was not the case for untrained 
individuals. However, there was no statistical group differ-
ence in the baseline measures. This suggests that the adapt-
ability of PF lies in the way it is under mechanical stress and 
a potentially faster recovery rate. A previous animal study 
demonstrated that not only its stiffness but also collagen 
FIGURE 4 
Relationship between the relative change (%Δ) in 
shear wave velocity (SWV) of the plantar fascia at the proximal site 
and %Δnavicular height (A) and %Δarch height ratio (B) in runners 
(closed circle) and untrained men (opened circle). The regression 
lines are shown with correlation coefficients in runners (bold line) and 
untrained men (dotted line)
1366 |   
SHIOTANI eT Al.
content, stress-relaxation, and hysteresis of connective tis-
sues were affected by the external loading during daily exer-
cises.25 It is speculated that the parameters such as viscosity, 
stress-relaxation, and hysteresis of PF are potential factors 
for the difference in mechanical fatigue response between 
runners and untrained individuals. Future studies address-
ing chronic effects of running on the viscoelastic properties 
of PF are needed.
It should be mentioned that smaller change in PF stiff-
ness in runners might also be attributable to the biomechan-
ical differences (eg, kinematics) during running, and indeed, 
runners showing higher values of SWV and navicular height 
were FFS while all untrained men were RFS (Figure 5). FFS 
are considered to receive higher mechanical stress on PF 
during running with higher velocity,12,14,15 which can be one 
of the reasons for the present results. Chronic effects of run-
ning with different patterns on PF properties are unknown at 
the moment, and further research is warranted to establish the 
optimal training and conditioning programs that allow injury 
prevention while being able to run faster.
PF stiffness as well as the foot arch recovered within 
60 minutes after running in both runners and untrained men. 
A previous study on collegiate runners reported that lowering 
of the foot arch remained for more than a week after a full 
marathon.2 It may be that the persistence of running-induced 
fatigue of PF and the arch flattening is related to the duration 
and intensity of running. As we attempted to set the protocol 
on overground running, mechanical loads were not measured. 
This is one of the limitations of the present study. However, it 
has been shown that there are differences in lower extremity 
kinematics between overground and treadmill running.36-38 
In addition, treadmill running has negligible effects on the 
foot arch flattening.35,39 Based on these findings, we decided 
to set the protocol at overground. Previous studies of 10-km 
running on a force-instrumented treadmill at a controlled 
intensity showed that even in competitive and recreational 
runners, there were different fatigue responses in kinematics 
and kinetics.34,40 Thus, it seems to be reasonable that runners 
and untrained individuals showed different fatigue responses 
in the present results. Since LDR is most often performed 
overground, we feel that our overground running setting was 
appropriate to investigate the association of PF and the foot 
arch in an athletic context. The effect of running duration/in-
tensity on PF and foot arch will lead to a better understanding 
of running-induced mechanical fatigue of PF.
In summary, this study revealed that LDR induced tran-
sient and site-specific decreases in PF stiffness, indicating 
occurrence of mechanical fatigue. Furthermore, the majority 
of running-induced lowering of foot arch can be attributed to 
the reduction of PF stiffness. Long-distance runners showed 
smaller changes in PF properties and foot deformation after 
running compared with untrained individuals. Our results 
strongly support a current concept that PF is a primary sup-
porting structure of the foot arch, both of which have positive 
adaptability in response to running training.
5 | 
PERSPECTIVES
There are clinical implications for our findings. First, our 
results highlight that LDR brings about mechanical fatigue 
primarily in the proximal site of PF. This finding coincides 
with the pathology of plantar fasciitis. Second, such hetero-
geneous mechanical properties of the PF depend on run-
ning experience. Well-experienced runners can build up 
resilient PF that minimize the risk of running-related inju-
ries. Future studies will enable a better understanding of the 
optimal training/conditioning schemes that allow PF injury 
prevention while improving its function as a spring during 
running.
ACKNOWLEDGEMENTS
This study was supported by JSPS KAKENHI Grant Numbers 
19J14912 and 16H01870. This study was part of research ac-
tivities of the Human Performance Laboratory, Organization 
for University Research Initiatives, Waseda University. The 
authors express their gratitude to Dr Pavlos Evangelidis and 
Dr Takaki Yamagishi for grammatical corrections of the 
manuscript.
FIGURE 5 
Individual patterns of response in shear wave 
velocity of the plantar fascia at the proximal site and navicular height 
in runners and untrained men at pre- (closed and opened circle) and 
post-running (closed and opened square). Individual changes from 
pre- to post-running in runners and untrained men are connected with 
bold and dotted lines, respectively. Runners, forefoot strikers (FFS) in 
particular, show relatively higher shear wave velocity and navicular 
height at the baseline
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1367
SHIOTANI eT Al.
CONFLICT OF INTERESTS
No conflict of interest, financial or otherwise, is declared by 
the authors.
ORCID
Hiroto Shiotani 
 https://orcid.org/0000-0001-9214-4068 
Munekazu Naito 
 https://orcid.org/0000-0003-0618-0607 
Yasuo Kawakami 
 https://orcid.org/0000-0003-0588-4039 
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How to cite this article: Shiotani H, Mizokuchi T, 
Yamashita R, Naito M, Kawakami Y. Acute effects of 
long-distance running on mechanical and morphological 
properties of the human plantar fascia. Scand J Med Sci 
Sports. 2020;30:1360–1368. https://doi.org/10.1111/
sms.13690

Acute effects of long-distance running on mechanical and morphological properties of the human plantar fascia.
Shiotani, Hiroto,Mizokuchi, Tomohiro,Yamashita, Ryo,Naito, Munekazu,Kawakami, Yasuo