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Paper text:
the toes are in contact with the ground 
 approximately three - quarters of the stance phase during walking and distribute the load2 .
toes are also thought to play an important 
 role in the ability to stand firmly on the ground by stabilizing the body3 .
therefore , toe function is important to 
 preserving healthy daily activities such as standing , moving , and walking .
recently ,  floating toe  received attention as a possible cause of toe dysfunction3 , 4 . 

floating toe reportedly influences dynamic balance , stride length , and walking speed in 
 studies from japan .
previous studies concluded that floating toe results from excessive 
 dorsiflexion5 or a lack of 
 plantarflexion6 of the 
 metatarsophalangeal joint ( mtp ) .
fukuyama et al.3 defined floating toe as a condition in which the toe did not contact 
 the ground in the standing position and the weight did not shift to the toe during walking . 

floating toe is one of the most common complications of weil osteotomy , an effective 
 treatment for metatarsal overload7 , 8 . in japan
, there is a high incidence of 
 floating toe among infants and adults who have not undergone weil osteotomy3 , 4 . 
 despite the high incidence of floating toe in japan
toe grip strength ( tgs ) , an indication of toe flexor muscle strength , has also attracted 
 attention as an important clinical indicator .
tgs is related to foot structure , especially 
 that of the foot arch9 , 10 .
mickle et al.11 reported a correlation between toe flexor strength and toe 
 deformities ( e.g. hallux valgus , claw , or hammer toe ) .
previous studies reported the association between floating toe and differences in arch 
 height percentage ( sitting vs. standing ) in adult females3 and birth weight in infants4 .
however , no study has investigated school age children . feet 
 maintain an almost constant growth rate , which is the same in both genders , until 12  years 
 of age12 .
therefore , it may be easier to 
 improve floating toe before 12  years of age using appropriate interventions . to implement 
 appropriate interventions , it is first necessary to investigate the factors associated with 
 floating toe in school age children .
the aim of this study was to investigate the 
 correlation between floating toe and tgs in school age children .
a total of 635 ( 1,270 feet ) japanese children ( boys , n=334 , age=10.2  0.7  years ; girls , 
 n=301 , age=10.3  0.7  years ; mean  sd ) participated in this study .
the participants were 
 recruited from five elementary schools in the nara prefecture in japan . signed consent
was 
 obtained from the principals of these schools for inclusion of their students in this study . 

we explained the 
 purpose and methods of the study to the participants and teachers of each elementary school 
 with a verbal statement and document .
the methods and procedures of the study were in 
 accordance with guidelines approved by the kyoto university graduate school of medicine and 
 the declaration of human rights , helsinki , 1975 .
the protocol of this study was approved by 
 the ethical committee of the kyoto university graduate school of medicine ( r0109 ) .
information on age , gender , height , and weight was obtained with a questionnaire .
the 
 rohrer index , which has been validated in school age children13 , was calculated as body weight ( kg)/height ( m ) .
images of each footprint were obtained using a foot printer ( bauerfeind ag , zeulenroda , 
 germany ) to screen for floating toe .
static footprint images were obtained as each 
 participant stood barefoot on the foot printer in the resting position as described by 
 tashiro et al.9 ( with feet shoulder - width 
 apart and in a neutral position ) .
floating toe was diagnosed if there was no visible 
 toe imprint . a previous study4 that used 
 the same foot printer as used here , calculated the score according to the number of 
 non - contacting toes and conducted a correlation analysis .
however , there has been no 
 established standard subgrouping of floating toe ; hence , two categories and new analysis 
 methods were used in the current study .
tgs was measured using a toe grip dynamometer ( t.k.k.3362 ; takei scientific instruments 
 co. , ltd . ,
participants sat on a chair without 
 leaning on the backrest with both hips and knees flexed at 90 and with the ankles in a 
 neutral position and fixed with a strap .
the first proximal phalanx was positioned at the 
 grip bar , while the heel was fixed by the heel stopper to prevent slipping during 
 measurement .
participants gripped the grip bar using their toe with maximal effort for 3 
 seconds .
the tgs measurements were carried out alternately in each foot and then repeated 
 once .
a foot - based analysis of all 1,270 feet ( both right and left feet of all 635 participants ) 
 was carried out .
all feet were classified into the floating toe group or the normal toe 
 group .
a multivariate 
 logistic regression analysis with generalized estimating equations adjusted for age , gender , 
 and rohrer index was used to determine whether tgs was associated with floating toe .
the 
 dependent variable was with or without floating toe ( floating toe group=1 ; normal toe 
 group=0 ) , while the independent variable was the tgs value .
results are presented as odds 
 ratio ( or ) with 95% confidence intervals ( ci ) .
the statistical analysis was performed using 
 spss version 20.0 ( ibm corp . , armonk , new york , usa ) , and values of p<0.05 were 
 considered significant .
the participants demographic data are shown in table 
 1table 1.participant characteristicsall ( n=635)male ( n=334)female ( n=301)9y ( n=55)10y ( n=143)11y ( n=136)9y ( n = 49)10y ( n=119)11y ( n=133)age ( years)10.3  0.7height ( cm)141.5  7.9134.4  5.3139.3  5.8145.1  7.3133.6  5.3140.8  6.8146.5  7.1weight ( kg)35.3  7.931.0  5.634.6  6.937.5  8.330.4  7.633.9  6.438.6  8.6rohrer index ( kg / m)12.4  1.812.7  1.512.7  2.012.2  1.812.6  2.212.1  1.512.1  1.8sd : standard deviation .
the floating toe group 
 had a lower mean tgs than the normal toe group ( 12.9  3.7  kg vs. 13.6  4.1  kg , 
 respectively ; p=0.001 ) .
table 2table 2.logistic regression analysisfloating toeor ( 95% ci)age ( years)0.982 ( 0.8301.162)gender - male1 ( reference)female0.873 ( 0.6961.096)rohrer index ( kg / m)0.995 ( 0.9891.001)tgs ( kg)*0.954 ( 0.9250.984)or : odds ratio ; 95% ci : 95% confidence interval ; tgs : toe grip strength ; rohrer 
 index : body weight ( kg)/height ( m).*p<0.01 shows the results of the logistic regression analysis . a low tgs was 
 independently associated with floating toe after the adjustment for age , gender , and rohrer 
 index ( or , 0.954 ; 95% ci , 0.9250.984 ; p=0.003 ) .
sd : standard deviation or : odds ratio ; 95% ci : 95% confidence interval ; tgs : toe grip strength ; rohrer 
 index : body weight ( kg)/height ( m ) .
this study investigated the association between floating toe and tgs in japanese children 
 aged 911  years .
we found that a low tgs was associated with floating toe even after the 
 adjustment for other factors .
although a causal relationship could not be determined between 
 these two factors because of the current study s cross - sectional design , maintaining a 
 normal toe position was found to be associated with a higher tgs .
a total of 512 feet ( 40.3% ) in this study had more than one floating toe .
araki et al.4 reported that at least one floating toe was 
 observed in > 87% of all 35  year - old children , while fukuyama et al.3 reported that 18 of 65 ( 27.7% ) healthy adult females in 
 their 20s had floating toes . while most studies have used different methods to evaluate 
 floating toes , there is a tendency toward a decreasing incidence with age .
this age - related 
 difference may be due to differences in tgs . according to one footprint analysis12
, feet maintain an almost constant growth 
 rate from 3 to 12  years of age .
in the same way , tgs may also develop with age until age 
 12  years .
therefore , if someone has a floating toe in childhood , this may be corrected to 
 normal with an increase in tgs .
a previous study14 investigated reference values for tgs among adults aged 
 2070  years .
however , reference values for tgs 
 among children and teenagers until 19  years of age have not been elucidated .
thus , further 
 studies of tgs in this age group are necessary . according to our logistic regression analysis
previous studies6 , 16 reported that the windlass mechanism may 
 be responsible for post - osteotomy floating toe .
tgs is exerted mainly by the plantar 
 intrinsic and extrinsic muscles17 , which 
 play a role in the windlass mechanism .
the mechanism also works in reverse , such that increased body 
 weight tends to flatten the arch , with associated flexion of the toes18 .
therefore , it is possible that a low tgs indicates 
 immaturity of the reverse windlass mechanism , which may lead to floating toe .
it is possible that the toe flexor 
 muscles are stretched by the condition of floating toe with the resulting toe extension . 

optimal muscle length is needed to exert maximum strength of the plantar flexors at a 
 certain angle of the ankle19 . in floating 
 toe
fukuyama et al.3 asserted that various lifestyle factors are involved in the 
 occurrence of floating toe , such as play in childhood , exposure to sports , and footwear . 

our finding implies that increasing tgs may be a key factor in preventing floating toe . 

hashimoto et al.10 studied strength 
 training of the intrinsic flexor muscles of the foot . however , the training studied therein , 
 which involved joint - flexing exercises of 200 repetitions once per day three times per week 
 for 8 weeks with a 3-kg load , is too heavy a burden for children . therefore , longitudinal 
 studies that investigate effective methods of increasing tgs in children and preventing 
 floating toe are needed .
it was previously shown that toe flexor muscle strength is 
 consistently associated with dynamic balance20 . accordingly
, early prevention of floating toe with increasing tgs 
 may improve dynamic balance ability in daily life .
first , owing to its cross - sectional design , a definite 
 causal relationship between floating toe and tgs can not be concluded .
second , our evaluation 
 of floating toe was done using a foot printer , which is limited to evaluations of the 
 stationary posture .
therefore , a new attempt to evaluate whether floating toe can be seen in dynamic motion , 
 such as walking , is necessary . because the foot printer is a simple and convenient piece of 
 portable equipment
tgs and footprint images were measured as 
 described by previous studies ; however , it may be necessary to investigate tgs measurements 
 in weight - bearing positions in the future .
finally , a simple visual evaluation of the 
 presence of floating toe was performed . despite these limitations ,
our findings suggest a 
 significant correlation between floating toe and tgs in school age children .
for the first 
 time , an association between the number of floating toes and tgs was shown .
[ purpose ] this study investigated the association between floating toe and toe grip 
 strength . [ subjects and methods ] a total of 635 japanese children aged 911  years 
 participated in this study . floating toe was evaluated using footprint images , while toe 
 grip strength was measured using a toe grip dynamometer . 
 all 1,270 feet were classified 
 into a floating toe group and a normal toe group according to visual evaluation of the 
 footprint images . 
 intergroup differences in toe grip strength were analyzed using the 
 unpaired t - test and logistic regression analysis adjusted for age , gender , and rohrer 
 index . 
 [ results ] there were 512 feet ( 40.3% ) in the floating toe group . mean toe grip 
 strength of the feet with floating toe was significantly lower than that of normal feet 
 ( floating toe group , 12.9  3.7  kg ; normal toe group , 13.6  4.1  kg ) . 
 in addition , lower 
 toe grip strength was associated with floating toe on logistic regression analysis after 
 adjustment for age , gender , and rohrer index ( odds ratio , 0.954 ; 95% confidence interval , 
 0.9250.984 ) . 
 [ conclusion ] this study revealed that lower toe grip strength was 
 significantly associated with floating toe . 
 therefore , increasing toe grip strength may 
 play a role in preventing floating toe in school age children .