Yokozuka et al. Journal of Foot and Ankle Researchhttps://doi.org/10.1186/s13047-020-00411-1(2020) 13:44

RESEARCH

Open AccessCorrelation between functional ability, toe
flexor strength, and plantar pressure ofhallux valgus in young female adults: across-sectional study
Mieko Yokozuka1*, Kanako Okazaki1, Yuko Sakamoto2 and Koko Takahashi2

Abstract
Background: The prevalence of hallux valgus (HV) increases with age in females. Several studies have investigated
the relationship between foot problems, including HV, and falls in older individuals. This study aimed to examine
whether HV causes a decline in functional activity in young females and also evaluate the relationship between HV
angle, functional activity, toe flexor strength, and plantar pressure.
Methods: We assessed 94 females (mean age, 19.6 ± 1.3 years; mean body mass index, 21.2 ± 2.0 kg/m2) not
currently receiving treatment for lower limb disease. HV angle was determined using their footprint. Functionalreach (FR) and maximum step length (MSL), toe flexor strength, and plantar pressure were measured. Plantarpressure was measured during walking. We also calculated FR and the pressure in eight regions (first toe, second
through fifth toes, first metatarsal, second through fourth metatarsals, fifth metatarsal, midfoot, medial heel, andlateral heel).
Results: There were 39 and 55 participants in the HV and no HV groups, respectively. FR and MSL did not differ
significantly between the HV and no HV groups. Toe flexor strength was significantly different between the HV andno HV groups (26.69 ± 9.68 vs. 32.19 ± 8.55, respectively) (p = 0.002, β = 0.206). During walking, plantar pressure wassignificantly lower in the second through fifth toes in the HV group (p = 0.005, β = 0.187). During FR, plantarpressure was significantly greater in the first metatarsal in the HV group (p = 0.016, β = 0.338). HV angle wasnegatively correlated with toe flexor strength (r = − 0.315, p = 0.002, β = 0.121) and plantar pressure during walking
in the second through fifth toes (r = − 0.362, p < 0.001, β = 0.047), and positively correlated with plantar pressureduring FR in the first metatarsal (r = 0.308, p = 0.002, β = 0.137). Toe flexor strength was negatively correlated withplantar pressure during FR in the second through fourth metatarsals (r = − 0.318, p = 0.002, β = 0.115), and there
was a positive correlation with MSL (r = 0.330, p = 0.001, β = 0.092).
Conclusions: This study confirmed that HV reduces toe flexor strength and affects forefoot pressure during walking
and FR in young females. Moreover, the toe flexor strength affects MSL. Efforts to prevent the onset anddeterioration of HV from a young age might help reduce the risk of falling when older.
Keywords: Hallux valgus, Toe flexor strength, Functional reach, Maximum step length, Plantar pressure* Correspondence: yokozuka@fmu.ac.jp
1
Preparing Section for New Faculty of Medical Science, Fukushima Medical
University, 1 Hikariga-oka, Fukushima 960-1295, Japan
Full list of author information is available at the end of the article© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to thedata made available in this article, unless otherwise stated in a credit line to the data.

Yokozuka et al. Journal of Foot and Ankle Research(2020) 13:44

Background
Foot pain and deformity are associated with falls incommunity-dwelling older persons [1, 2]. One metaanalysis indicated that persons who have falls are more
likely to have foot pain and hallux valgus (HV) with odds
ratios of 1.95 and 1.89, respectively [2]. Another metaanalysis reported that the prevalence of HV in persons
over 65 years was 35.7%, which was higher in females
than in males [3]. Similarly, a study of 268 Japanese females aged ≥65 years living in the community, 99(36.9%) were diagnosed with HV [4].
HV and lesser toe deformities significantly reduce theflexor strength of the hallux and lesser toes [5–7]. The
relationship between HV and physical function [8], spatiotemporal gait parameters [9], balance [10, 11], timed
up and go test [12], and plantar pressure have been reported [7, 8, 13–15]. However, the participants of thesestudies were middle-aged or older people, and the studies also included persons with mobility and ADL limitations [10, 11], with aids [5] or assistive devices [13], withfoot pain or previous treatment [7], with knee osteoarthritis [8], and those with indications for surgery [14].
Therefore, factors other than HV may have been involved, and the deterioration in physical function, balance, and plantar pressure may have been due to aging.
On the other hand, about 30% of female university
students in Japan are reported to have HV [16, 17]. It
has been reported that young women need to be moreaware of the characteristics and severity of HV [16]. To
reduce the risk of falls in old age, it is important to prevent the onset and deterioration of HV among young females. To this end, it is necessary to clarify the effects of
HV on motor function, even in young females. Toe
flexor muscles become more active in the mid stance to
toe off during walking [18, 19], and toe flexor strength
was significantly correlated with the anterior limit of thefunctional base of support [20]. Therefore, even in young
people, if the toe flexor strength is reduced due to hallux
valgus, there is concern that it may affect the forward
movement of the center of gravity and the motion with
propulsive force in daily life.
This study aimed to compare dynamic balance in forward reaching/stepping tasks in young females with andwithout HV. In addition, the relationship among functional activity, toe flexor strength, and plantar pressure
was assessed.
Methods
ParticipantsThis cross-sectional study of 94 female university students was conducted from December 2019 to January
2020. The purpose of the study was explained to all participants in both written and verbal forms, and written
informed consent was obtained. The study was approved

Page 2 of 6

by the University’s Ethics Committee (Approval number:
2019–187). The exclusion criteria were age > 25 years
and the presence of lower limb disorders.
Measurements

All measurements were performed with the participants
barefoot.
HV angle

Measurement of HV was conducted using a foot printer(Bauerfeind, Germany), and a footprint was taken withthe participant in the standing position. The angle between the line connecting the first metatarsal head andthe first proximal phalanx head, and that connecting thefirst metatarsal head and the calcaneus in the posterior
medial malleolus position on the outline from the footprint was measured [21]. This angle is highly correlatedwith the HV angle on X-ray (r = 0.942), and a 16° HVangle on the footprint is equivalent to a 20° diagnosis of
HV on X-ray [21].
Functional reach (FR)Participants stood upright and raised both arms toshoulder height, and the position of the top of the middle finger was marked. After that, participants stretched
their arms forward as far as possible for 5 s, with theirlegs fixed. The maximum distance of the position of the
top of the middle finger from the first position was recorded [22]. This action was performed twice, and the
maximum value was taken as the result. FR was normalized by height (FR / height * 100). Studies have shown
acceptable reliability of the FR [22].
Maximum step length (MSL)

Participants were instructed to stand with both feet in
the indicated position and step forward as far as possible
with their right/left leg and bring the other leg up to thefirst leg in one step. In this position, the stepped distance was recorded. When the participant lost balance,
the distance was measured again. This action was performed twice on each side and the maximum value oneach side was taken as their result [23]. MSL was normalized by height (MSL / height * 100). MSL shows thebest intraclass correlation coefficients [23, 24].
Toe flexor strength

Toe flexor strength was measured using a toe grip dynamometer (T.K.K. 3364b; Takei Scientific Instruments,
Niigata, Japan). The hip, knee, and ankle joints were set
to 90° in a chair sitting position, and the ankle was secured with a belt to prevent the bar being pulled by the
ankle dorsiflexion. The bar for measuring toe flexor
strength was gripped for 3 s with maximal effort using
the toes for the left and right side, respectively. Care wasYokozuka et al. Journal of Foot and Ankle Research(2020) 13:44

taken to prevent the bar being pulled by flexion of theknee joint. Toe flexor strength was measured twice oneach side with a rest of 3 to 5 s to minimize the effect on
the second measurement. The maximum toe flexor
strength on each side was normalized by body weight(toe flexor strength / body weight * 100). The intra- andinter-rater reliability of toe grip dynamometer measurements have been validated [25].

Page 3 of 6

Table 1 Characteristics of participants
HV group (n = 39) no HV group (n = 55) p-value
HV angle (°) (range) 20.3 ± 5.1 (4–15)

11.0 ± 2.6 (16–43)< 0.001Age (years)

19.4 ± 1.2

19.8 ± 1.3

0.186

Height (cm)157.4 ± 4.7

156.8 ± 5.7

0.628

Weight (kg)52.8 ± 4.3

52.1 ± 6.2

0.521

2

21.3 ± 1.8

21.2 ± 2.2

0.425

BMI (kg/m )BMI body mass index, HV hallux valgus

Plantar pressure

Plantar pressure was measured during walking and FR.
The plantar pressure was measured using a foot analyzer(Gaitview UGA-526; aison, Inc., Saitama, Japan), which
includes a 410 × 410 × 3-mm active area, comprising2304 (48 × 48) force sensitive resistor sensors. The average plantar pressure was automatically applied to thefoot in eight regions (first toe, second through fifth toes,
first metatarsal, second through fourth metatarsals, fifth
metatarsal, midfoot, medial heel, and lateral heel) using
software. Plantar pressure during walking was measured
using a two-step method of collecting plantar pressure
values similar to plantar pressure data obtained using
the midgait [26]. Walking started at approximately 80
cm from the front edge of the pressure platform and theplantar pressure of the second step was measured. Participants repeated the walking trial five times, and theaverage plantar pressure of five trials for each foot wascalculated.
Statistical analysis

For variables measured bilaterally (HV angle, MSL, toe
flexor strength, and plantar pressure during walking andFR), data from only one limb was analyzed to maintainindependence [27]. Participants were classified into HV
and no HV groups. For HV participants, the foot with agreater HV angle was chosen (31 right feet and eight leftfeet), while for no HV participants, the right foot or leftfoot was chosen (27 right feet and 28 left feet) randomlyusing random number sampling. Tests for normality
were performed with the Shapiro-Wilk test. FR, MSL,
toe flexor strength, and plantar pressure were comparedusing the unpaired T-test or Mann-Whitney U test. Furthermore, the correlation between HV angle, FR, MSL,
toe flexor strength, and plantar pressure was determinedusing the Spearman’s correlation coefficient, because it
includes variables with a non-normal distribution. Statistical analyses were performed using SPSS for Windows(version 25.0; IBM, Armonk, NY, USA), and the significance level was set at < 5%.

Results
The mean ± standard deviation (SD) age of the total
sample was 19.6 ± 1.3 years, and the mean body massindex (BMI) was 21.2 ± 2.0 kg/m2. Table 1 shows thecharacteristics of participants. The HV group had 39
participants, whereas the no HV group had 55
participants.
Table 2 shows FR, MSL, toe flexor strength, and plantar pressure. FR and MSL were not significantly different
in the HV and no HV groups. Toe flexor strength wassignificantly different at 26.69 ± 9.68 and 32.19 ± 8.55 for
the HV and no HV groups, respectively (p = 0.002,
β = 0.206). During walking, the plantar pressure in the
HV group was significantly reduced for the second
through fifth toes (p = 0.005, β = 0.187) and the second through fourth metatarsals (p = 0.014, β = 0.600),
and was significantly increased in the lateral heel(p = 0.044, β = 0.603). During FR, the plantar pressure
was significantly increased in the first metatarsal in
the HV group (p = 0.016, β = 0.338).
Table 3 shows the relationship between HV angle andtoe flexor strength. HV angle was negatively correlated with
toe flexor strength (r = − 0.315, p = 0.002, β = 0.121), plantar pressure during walking in the second through fifth toes(r = − 0.362, p < 0.001, β = 0.047) and the second throughfourth metatarsals (r = − 0.242, p = 0.019, β = 0.342), andthere was a positive correlation with plantar pressure during walking in the first toe (r = 0.253, p = 0.014, β = 0.301)
and the lateral heel (r = 0.301, p = 0.003, β = 0.154) andduring FR in the first metatarsal (r = 0.308, p = 0.002,
β = 0.137) and midfoot (r = 0.212, p = 0.040, β = 0.459).
Toe flexor strength was negatively correlated with plantarpressure during walking in midfoot (r = − 0.211, p = 0.041,
β = 0.463) and during FR in the second through fourth
metatarsals (r = − 0.318, p = 0.002, β = 0.115) and midfoot(r = − 0.348, p = 0.001, β = 0.064), and there was a positive
correlation with MSL (r = 0.330, p = 0.001, β = 0.092), during walking in the second through fifth toes (r = 0.226,
p = 0.029, β = 0.403), and during FR the first toe(r = 0.223, p = 0.031, β = 0.415).

Discussion
There was no difference in FR and MSL between the
HV and no HV groups. The anterior limit of the functional base of support was significantly correlated with
toe flexor strength [20]. On the other hand, the maximum balance test that participants leaned forward thenbackward as far as possible from the ankle without

Yokozuka et al. Journal of Foot and Ankle Research(2020) 13:44

Page 4 of 6

Table 2 FR, MSL, toe flexor strength, and plantar pressure
HV group (n = 39)

no HV group (n = 55)

p-valueβeffect size dFR (cm/cm*100)

21.39 ± 3.61

22.15 ± 3.54

0.309

0.827

0.214

MSL (cm/cm*100)

72.10 ± 5.78

73.95 ± 6.54

0.159

0.705

0.300

Toe flexor strength (kg/bw*100)

26.69 ± 9.68

32.19 ± 8.55

0.002**

0.206

0.602

T1

89.07 ± 22.65

79.41 ± 28.35

0.070

0.572

0.376

T25

61.33 ± 32.50

81.38 ± 32.50

0.005**

0.187

0.617

M1

104.74 ± 26.82

122.31 ± 52.56

0.055

0.506

0.421

M24

159.60 ± 11.88

172.92 ± 49.54

0.014*

0.600

0.370

M5

115.29 ± 24.03

121.20 ± 20.66

0.205

0.762

0.264

MF

102.91 ± 29.44

96.37 ± 39.01

0.379

0.854

0.189

MH

162.05 ± 7.96

163.01 ± 8.35

0.576

0.914

0.118

LH

168.63 ± 11.93

164.29 ± 11.69

0.044*

0.603

0.368

T1

59.23 ± 54.25

56.15 ± 49.83

0.985

0.941

0.059

T25

53.30 ± 39.26

62.64 ± 46.33

0.343

0.829

0.218

M1

105.82 ± 42.92

85.09 ± 37.44

0.016*

0.338

0.515

M24

133.13 ± 34.33

128.12 ± 29.50

0.220

0.888

0.157

M5

97.78 ± 40.45

105.52 ± 31.77

0.323

0.829

0.213

MF

70.32 ± 26.10

58.23 ± 31.04

0.050

0.487

0.422

MH

103.77 ± 34.39

110.34 ± 32.78

0.351

0.848

0.195

LH

103.70 ± 34.35

112.59 ± 30.71

0.347

0.757

0.273

Plantar pressure (kPa)
Gait

FR

FR functional reach, MSL maximum step length, HV hallux valgus, T1 first toe, T25 second through fifth toes, M1 first metatarsal, M24 second through fourth
metatarsals, M5 fifth metatarsal, MF midfoot, MH medial heel, LH lateral heel
* p < 0.05, ** p < 0.01

moving their feet is heavily involved with ankle
inversion-eversion ROM, and the maximal balance range
was not influenced by the presence or absence of HV[11]. As for the reason why there is no difference between FR and MSL in HV and no HV groups, young
women with HV may be adequately compensated using
different balance strategies, despite toe flexor strengthwith HV weakness.
There was a difference in toe flexor strength between
the HV and no HV groups. Also, HV angle and toe
flexor strength were negatively correlated. It has often
been reported that plantar flexion strength of HV decreases in older people [5–7]. The valgus / pronation of
the first phalanx associated with HV may relatively
shorten the length of the flexor hallucis muscles, making
it difficult to exert the toe flexor strength. Although it
was not possible to evaluate the muscle strengths of thehallux and lesser toes separately with the equipmentused, it became clear that even in young people, plantar
flexion strength was lower in those with HV.
There was no significant difference in pressure on thefirst toe during walking between the HV and no HVgroups. There are various reports on the pressure of thetoes during walking in older people. The HV showed nosignificant difference in plantar pressure of hallux during
walking and the pressures of the first and second metatarsals were significantly higher than those of no HV[13]. Many reports suggest that the first toe pressure on
HV during walking is low [7, 8, 28, 29]. Greater HV severity was associated with great toe pain and reduced
loading under the hallux when walking [29]. Conversely,
the pressure of the hallux during walking was significantly higher in women with mild HV than in those withno history of foot or lower limb problems [30]. The participants of this study were young persons with no painin the toes and no disability in the lower limbs. That is,
the participants did not avoid pain and were not affectedby other joint disorders. Even the HV may not have affected the pressure of the hallux during walking.
Furthermore, in the HV group, the pressures of thesecond through fifth toes and the second through fourth
metatarsals during walking were significantly lower, andthe pressure of the lateral heel was significantly higher
than that in no HV. From this result, it is consideredthat the load is applied to the outside by heel contact,
and the load is decreased from mid stance to toe off. In

(2020) 13:44

Page 5 of 6

Table 3 Correlations between HV angle and toe flexor strengthand FR, MSL and plantar pressurephalangeal joints in 0°–10° ankle dorsiflexion and in
25°–45° metatarsal phalangeal joint dorsiflexion [31].
Flexor muscles exert their most tension when themuscle length becomes long due to the two joint movements. The movement of MST includes metatarsal phalangeal joint dorsiflexion, but the movement of FR does
not include this joint movement. Also, similar to FR,
previous studies have reported that maximal balance
range does not depend on the presence or absence of
HV [11], with the most important independent predictor
noted as ankle dorsiflexion strength [10] and ankle
inversion-eversion ROM [11]. Therefore, in MST, more
toe flexor muscles were acting, but in FR, it may nothave been acting. That is, it is considered that there wasa significant relationship only between toe flexor
strength and MSL.
This study has some limitations. First, an HV angle of
16° or more indicated HV, as determined by the footprint. This angle would correspond to 20° on X-ray.
Therefore, an X-ray image showing an angle of 15° may
indicate mild HV, and it is possible that the no HVgroup included participants with mild HV. Second, pressure of the supporting foot in MSL could not be measured by the foot analyzer used in this study, and thepressure distribution with or without HV remains unknown. Third, FR and MSL were measured as functional
activities. These movements involve whole-body movements, and although their relationship with toe function
was recognized, involvement of other parts of the bodyother than the toes could not be ruled out. A relationship was observed between HV angle and toe flexor
strength, and between toe flexor strength and MSL, but
the causal relationship remains unknown.

Yokozuka et al. Journal of Foot and Ankle Research

HV angler
HV anglep-valueToe flexor strengthβrp-value β−0.315 0.002** 0.121

1.000

Toe flexor strength −0.315 0.002**

0.121 1.000

FR−0.007 0.949

0.950 0.198

0.056

MSL

−0.129 0.217

0.764 0.330

0.001** 0.092

T1

0.253

0.301 −0.038 0.718

T25−0.362 < 0.001** 0.047 0.226

0.029*

0.403

M1−0.138 0.186

0.736 0.013

0.899

0.948

M24

−0.242 0.019*

0.342 −0.067 0.520

0.901

M5

−0.091 0.385

0.860 −0.007 0.944

0.949

MF

0.163

0.116

0.650 −0.211 0.041*

0.463

MH

−0.168 0.106

0.632 −0.065 0.532

0.904

LH

0.301

0.003**

0.154 −0.132 0.205

0.754

T1

0.028

0.791

0.942 0.223

0.031*

0.415

0.515

Plantar pressure
Gait0.014*

0.935

FR

T25

−0.130 0.213

0.762 0.199

0.054

0.509

M1

0.308

0.002**

0.137 −0.135 0.195

0.745

M24

0.124

0.235

0.779 −0.318 0.002** 0.115

M5−0.144 0.166

0.716 −0.095 0.364

MF

0.212

0.459 −0.348 0.001** 0.064

MH−0.174 0.093

0.608 −0.193 0.062

0.534

LH

−0.198 0.056

0.517 −0.173 0.095

0.612

0.040*

0.852

FR functional reach, MSL maximum step length, HV hallux valgus, T1 first toe,
T25 second through fifth toes, M1 first metatarsal, M24 second through fourth
metatarsals, M5 fifth metatarsal, MF midfoot, MH medial heel, LH lateral heel
* p < 0.05, ** p < 0.01

HV, the ratio of the center of pressure excursion to thefoot width during walking is low, and it is pointed outthat foot pronation may occur [28]. In this study, although the center of pressure and foot posture were notmeasured, the tendency toward foot pronation in thehallux valgus is predicted due to the decrease in lateralpressure during walking.
In FR, when body weight was moved forward while
standing on both legs, the pressure on the first metatarsal in HV was higher compared to no HV group, but not
the pressure on the hallux and lesser toes. The varus of
the first metatarsal bone and the valgus / pronation of
the first phalanx that is associated with HV may increase
the most prominent pressure on the first metatarsophalangeal joint.
Toe flexor strength and MSL were positively correlated. However, toe flexor strength and FR were not correlated. Long and short toe flexor muscles produce
maximal voluntary moments around the metatarsal

Conclusions
In conclusion, the main finding of this study was that inyoung females with HV, toe flexor strength is significantly reduced and positively correlated with MSL. HValters foot loading patterns during walking and pressure
distribution during FR. Foot problems, including hallux
valgus, are associated with falls in old age. Attention
should be paid to the onset and deterioration of hallux
valgus from an early age.
Abbreviations
HV: Hallux valgus; FR: Functional reach; MSL: Maximum step length
Acknowledgements
We thank all the participants in the study.
Authors’ contributions
MY participated in the study design, participants recruitment, dataacquisition, analysis, interpretation and drafting of the manuscript. KO
assisted with data acquisition and analysis. YS and KT assisted withparticipants recruitment. All authors read and approved the final manuscript.

Yokozuka et al. Journal of Foot and Ankle Research(2020) 13:44

Funding
Research funds allocated from the University were used.
Availability of data and materials
Not applicable.
Ethics approval and consent to participate
The study was approved by the University’s Ethics Committee (Approval
number: 2019–187). Written informed consent was obtained from allparticipants.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Preparing Section for New Faculty of Medical Science, Fukushima Medical
University, 1 Hikariga-oka, Fukushima 960-1295, Japan. 2School of Nursing,
Fukushima Medical University, 1 Hikariga-oka, Fukushima 960-1295, Japan.
Received: 17 March 2020 Accepted: 2 July 2020

References
1. Stubbs B, Binnekade T, Eggermont L, Sepehry AA, Patchay S, Schofield P.
Pain and the risk for falls in community-dwelling older adults: systematic
review and meta-analysis. Arch Phys Med Rehabil. 2014;95:175–87.e9.
https://doi.org/10.1016/j.apmr.2013.08.241.
2. Menz HB, Auhl M, Spink MJ. Foot problems as a risk factor for falls incommunity-dwelling older people: a systematic review and meta-analysis.
Maturitas. 2018;118:7–14. https://doi.org/10.1016/j.maturitas.2018.10.001.
3. Nix S, Smith M, Vicenzino B. Prevalence of hallux valgus in the general
population: a systematic review and meta-analysis. J Foot Ankle Res. 2010;3:
21. https://doi.org/10.1186/1757-1146-3-21.
4. Nishimura A, Fukuda A, Nakazora S, Uchida A, Sudo A, Kato K, et al.
Prevalence of hallux valgus and risk factors among Japanese community
dwellers. J Orthop Sci. 2014;19:257–62. https://doi.org/10.1007/s00776-0130513-z.
5. Mickle KJ, Munro BJ, Lord SR, Menz HB, Steele JR. ISB Clinical Biomechanics
Award 2009: toe weakness and deformity increase the risk of falls in older
people. Clin Biomech (Bristol, Avon). 2009;24:787–91. https://doi.org/10.
1016/j.clinbiomech.2009.08.011.
6. Nix SE, Vicenzino BT, Smith MD. Foot pain and functional limitation in
healthy adults with hallux valgus: a cross-sectional study. BMC
Musculoskelet Disord. 2012;13:197. https://doi.org/10.1186/1471-2474-13197.
7. Hurn SE, Vicenzino B, Smith MD. Functional impairments characterizing
mild, moderate, and severe hallux valgus. Arthritis Care Res (Hoboken).
2015;67:80–8. https://doi.org/10.1002/acr.22380.
8. Nishimura A, Ito N, Nakazora S, Kato K, Ogura T, Sudo A. Does hallux valgus
impair physical function? BMC Musculoskelet Disord. 2018;19:174. https://doi.org/10.1186/s12891-018-2100-0.
9. Misu S, Doi T, Asai T, Sawa R, Tsutsumimoto K, Nakakubo S, et al.
Association between toe flexor strength and spatiotemporal gaitparameters in community-dwelling older people. J Neuroeng Rehabil. 2014;
11:143. https://doi.org/10.1186/1743-0003-11-143.
10. Menz HB, Morris ME, Lord SR. Foot and ankle characteristics associated with
impaired balance and functional ability in older people. J Gerontol A Biol
Sci Med Sci. 2005;60A:1546–52. https://doi.org/10.1093/gerona/60.12.1546.
11. Spink MJ, Fotoohabadi MR, Wee E, Hill KD, Lord SR, Menz HB. Foot andankle strength, range of motion, posture, and deformity are associated withbalance and functional ability in older adults. Arch Phys Med Rehabil. 2011;
92:68–75. https://doi.org/10.1016/j.apmr.2010.09.024.
12. Uritani D, Fukumoto T, Matsumoto D, Shima M. The relationship between
toe grip strength and dynamic balance or functional mobility amongcommunity-dwelling Japanese older adults: a cross-sectional study. J Aging
Phys Act. 2016;24:459–64. https://doi.org/10.1123/japa.2015-0123.

Page 6 of 6

13. Mickle KJ, Munro BJ, Lord SR, Menz HB, Steele JR. Gait, balance and plantarpressures in older people with toe deformities. Gait Posture. 2011;34:347–51.
https://doi.org/10.1016/j.gaitpost.2011.05.023.
14. Hofmann UK, Götze M, Wiesenreiter K, Müller O, Wünschel M, Mittag F.
Transfer of plantar pressure from the medial to the central forefoot inpatients with hallux valgus. BMC Musculoskelet Disord. 2019;20:149. https://doi.org/10.1186/s12891-019-2531-2.
15. Hida T, Okuda R, Yasuda T, Jotoku T, Shima H, Neo M. Comparison ofplantar pressure distribution in patients with hallux valgus and healthy
matched controls. J Orthop Sci. 2017;22:1054–9. https://doi.org/10.1016/j.jos.
2017.08.008.
16. Okuda H, Juman S, Ueda A, Miki T, Shima M. Factors related to prevalenceof hallux valgus in female university students: a cross-sectional study. J
Epidemiol. 2014;24:200–8. https://doi.org/10.2188/jea.JE20130110.
17. Yokozuka M, Okazaki K, Sakamoto Y, Takahashi K. Relationship between footmorphology and toe muscle strength in female university students. J Phys
Ther Sci. 2019;31:457–61. https://doi.org/10.1589/jpts.31.457.
18. Mann R, Inman VT. Phasic activity of intrinsic muscles of the foot. J Bone
Joint Surg Am. 1964;46:469–81.
19. Gray EG, Basmajian JV. Electromyography and cinematography of leg andfoot ("normal" and flat) during walking. Anat Rec. 1968;161:1–15.
20. Endo M, Ashton-Miller JA, Alexander NB. Effects of age and gender on toe
flexor muscle strength. J Gerontol A Biol Sci Med Sci. 2002;57:M392–7.
https://doi.org/10.1093/gerona/57.6.M392.
21. Shimizu S, Maeda T, Kato Y, Sasaki K, Uchida T. Effective evaluation of hallux
valgus angle and digitus quintus varus angle for footprint. J Jpn Soc Surg
Foot. 2010;31:35–9 [in Japanese with English abstract].
22. Duncan PW, Weiner DK, Chandler J, Studenski S. Functional reach: a newclinical measure of balance. J Gerontol. 1990;45:M192–7. https://doi.org/10.
1093/geronj/45.6.M192.
23. Bongers KT, Schoon Y, Graauwmans MJ, Hoogsteen-Ossewaarde ME, Olde
Rikkert MG. Safety, feasibility, and reliability of the maximal step length, gait
speed, and chair test measured by seniors themselves: the senior step study. J
Aging Phys Act. 2015;23:438–43. https://doi.org/10.1123/japa.2013-0231.
24. Schoon Y, Weerdesteyn V, Stunnenberg A, Olde Rikkert MG. Sense andsimplicity: maximum step length is also reliable, feasible, and valid in very
old adults. J Am Geriatr Soc. 2010;58:2444–5. https://doi.org/10.1111/j.15325415.2010.03193.x.
25. Uritani D, Fukumoto T, Matsumoto D. Intrarater and interrater reliabilities fora toe grip dynamometer. J Phys Ther Sci. 2012;24:639–43. https://doi.org/10.
1589/jpts.24.639.
26. McPoil TG, Cornwall MW, Dupuis L, Cornwell M. Variability of plantarpressure data. A comparison of the two-step and midgait methods. J Am
Podiatr Med Assoc. 1999;89:495–501. https://doi.org/10.7547/87507315-8910-495.
27. Menz HB. Two feet, or one person? Problems associated with statisticalanalysis of paired data in foot and ankle medicine. Foot. 2004;14:2–5.
https://doi.org/10.1016/S0958-2592(03)00047-6.
28. Galica AM, Hagedorn TJ, Dufour AB, Riskowski JL, Hillstrom HJ, Casey VA,
et al. Hallux valgus and plantar pressure loading: the Framingham footstudy. J Foot Ankle Res. 2013;6:42. https://doi.org/10.1186/1757-1146-6-42.
29. Clarke GR, Thomas MJ, Rathod-Mistry T, Marshall M, Menz HB, Peat G, et al.
Hallux valgus severity, great toe pain, and plantar pressures during gait: across-sectional study of community-dwelling adults; 2020. https://doi.org/10.
1002/msc.1472.
30. Martínez-Nova A, Sánchez-Rodríguez R, Pérez-Soriano P, Llana-Belloch S,
Leal-Muro A, Pedrera-Zamorano JD. Plantar pressures determinants in mild
Hallux Valgus. Gait Posture. 2010;32:425–7. https://doi.org/10.1016/j.gaitpost.
2010.06.015.
31. Goldmann JP, Brüggemann GP. The potential of human toe flexor muscles
to produce force. J Anat. 2012;221:187–94. https://doi.org/10.1111/j.14697580.2012.01524.x.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.