walking is an essential movement and is the most frequently performed action by human 
 beings1 .
racewalking is an olympic 
 event , and the popularity of racewalking has increased steadily .
racewalking has not yet 
 attracted large numbers of adolescents in china , but there appear to be indications that the 
 event is growing in popularity .
racewalking events of 5 and 10  km are becoming increasingly 
 popular for amateur athletes , and successes in these relatively short events have inspired 
 some teenagers to attempt longer distance races .
a number of walking enthusiasts have 
 attributed the rising popularity of racewalking to decline in the popularity of jogging , and 
 this trend has been influenced by widespread belief that racewalking is a sport providing 
 opportunities for competitions , as well as valuable health and fitness benefits , without 
 significant risk of injury2 .
sports fatigue , which is an inevitable feature in the career of any athlete , is both a 
 physical and a mental state , representing the state in a difficult training session or 
 competition when the body demonstrates a reduced ability to work efficiently . in longer 
 activities such as distance running and racewalking , fatigue will arise through a combined 
 effect of muscle repetition and depleted energy stores , especially local muscular fatigue 
 that can be caused by insufficient energy to perform the legally specific technique and 
 increased levels of muscular discomfort that may cause the body to shift into deviated 
 biomechanics state .
previous research has shown that success in race walking is related more to the efficiency 
 of technique rather than physiological factors3 .
the kinematics of the forefoot in racewalking are triplanar 
 motions . since the axis of the subtalar joint is not in any cardinal plane , the motions 
 occurring in the subtalar joint present a triplanar motion pattern .
the triplanar motions of 
 the forefoot are as follows : transverse motion , frontal motion , and sagittal motion .
the 
 transverse motions occurring primarily in the subtalar joint are composed of medial 
 rotation , which is movement of the forefoot or part of the foot medially in the horizontal 
 plane , and lateral rotation , which is movement of the forefoot or part of the foot laterally 
 in the horizontal plane . during running , both a medial and a lateral rotation were observed 
 in the footprint when comparing the rear foot and forefoot in the horizontal plane4 .
there are significantly differences between 
 racewalking and normal walking or jogging during the stance phase ( closed kinematic chain 
 motions ) of the gait cycle .
this is because racewalking demands a straight leg from when the 
 support leg touches ground until to the vertical upright position relative to the ground is 
 reached .
keeping the leg straight with introversion of the foot causes a torque to be 
 applied to the knee and this may be a potential factor for lower extremity injuries .
racewalkers often use treadmills because of the benefits of having a flat unchanging 
 surface on which pace judgment can be learned5 .
the effects of fatigue associated with racewalking on a treadmill 
 have not been evaluated and could be informative in regard to maintenance of the legal 
 technique .
the purpose of this study was to investigate the association of the forefoot s 
 kinematic variables ( medial and lateral rotation ) in the horizontal plane with the 
 racewalking linear speed during progressive pace treadmill racewalking in the fatigue state 
 after a physically demanding aerobic exercise load .
the participants were 
 students of the huaian sports school of huaian city , china . to be included in the study , 
 each participant was required to have been trained at the school for at least 3  years .
the 
 subjects characteristics are detailed in table 
 1table 1.characteristics of the subjects ( n=11)age ( years)16.31.9weight ( kg)58.410.1height ( cm)177.810.7data are presented as the mean  sd .
data are presented as the mean  sd participants were excluded if they had a lower limb or foot injury , visual problems , or 
 vestibular problems .
the subjects signed an informed document approved by the ethics 
 committee of jangsu province huaian sports school , which also approved the study . before the 
 testing session ,
all of the participants were supervised while they performed a 10-minute 
 conventional routine warm - up .
the participants were asked to refrain from any exercise for 2 
 hours before testing .
we measured the forefoot maximum 
 medial / lateral rotation with an 8 ch wireless motion recorder ( mvp - rf8-bc , microstone inc .
, 
 saku , japan ) during progressive pace racewalking before and after a physically demanding 
 aerobic exercise load , which consisted of racewalking 5  km on the instrumented treadmill at 
 a pace equivalent to 100% of their recent best load intensity .
the wireless motion recorder 
 was adhered to the third and forth metatarsal above the right foot .
the sampling rate used 
 for detecting the forefoot maximum medial / lateral rotation in the horizontal plane with the 
 wireless motion recorder ( bluetooth ) was 200  hz .
the data were collected for 6 seconds on 
 five successive capture stages , and the subjects maintained the appropriate pace for each 
 stage , 2  km / h , 4  km / h , 6  km / h , 8  km / h and 10  km / h for about 30 seconds each without a rest 
 break .
the motion characteristics of the participants in 3 consecutive gait cycles at each 
 of the 5 speeds were recorded and analyzed with the mvp - rf8-bc analysis software system .
a 
 video camera ( 200 fps ) was simultaneously used to record the cycle phases and technique .
two - way analysis of variance and multiple comparisons ( bonferroni ) were used to test for 
 statistically significant differences in forefoot maximum medial / lateral rotation in the 
 horizontal plane before and after physically demanding aerobic exercise load during 
 progressive pace racewalking , and the factors examined were before and after the physically 
 demanding aerobic exercise load and the 2  km / h , 4  km / h , 6  km / h , 8  km / h , and 10  km / h paces . 

if a significant interaction was found , one - way analysis of variance was performed for each 
 factor .
the independent t - test was performed to compare between before and 
 after the physically demanding aerobic exercise load .
the associations between the forefoot 
 maximum medial / lateral rotation and paces were determined by pearson s product moment 
 correlation .
the results for forefoot maximum medial / lateral rotation in the horizontal plane during 
 progressive pace treadmill racewalking are shown in tables 2table 2.comparison between pre- and post- intervention values of m / lr ( )pacesbefore - interventionafter - intervention2 km / h3.70.54.20.84 km / h5.30.65.30.5 6 km / h6.11.07.00.98 km / h6.30.99.61.3**10 km / h6.90.710.51.7**data are presented as the mean  sd .
significant differences after the physically demanding aerobic exercise load : 
 * p<0.05 ; * * p<0.01 .
m / lr : medial / lateral rotation and 3table 3.correlation coefficient values of progressive paces and m / lr during racewalking 
 on a treadmillcorrelation coefficient ( r)before the exercise load0.7 * * after the exercise lod0.9 * * * p<0.05 ; * * p<0.01 .
two - way analyses of variance showed that there were main effects in the 
 statistics between before and after the physically demanding aerobic exercise load .
the 
 independent t - test showed after the physically demanding aerobic exercise 
 load , there were no significant differences in forefoot maximum medial / lateral rotation at 
 the 2  km / h , 4  km / h , and 6  km / h paces compared with before the physically demanding aerobic 
 exercise load and that there were significant differences in forefoot maximum medial / lateral 
 rotation at the 8  km / h and 10  km / h paces compared with before the physically demanding 
 aerobic exercise load .
there were significant associations between the forefoot maximum 
 medial / lateral rotation and increased paces during progressive pace treadmill racewalking , 
 especially after intervention after the physically demanding aerobic exercise load .
significant differences after the physically demanding aerobic exercise load : 
 * p<0.05 ; * * p<0.01 .
the aims of this study were to evaluate the changes in forefoot maximum medial / lateral 
 rotation and to investigate whether the forefoot maximum medial / lateral rotation in the 
 horizontal plane is associated with increased paces during progressive pace treadmill 
 racewalking in the fatigue state after a physically demanding aerobic exercise load .
there 
 were no statistically significant differences in forefoot maximum medial / lateral rotation 
 when the speed was set to 2  km / h , 4  km / h or 6  km / h .
this implies that the speeds intensity 
 was too slow to change the forefoot s kinematic parameters even though the subjects were in 
 a fatigue state .
the significant associations between forefoot maximum medial / lateral 
 rotation and progressive paces might indicate that the motor skill of the participants were 
 biomechanically constrained by increased paces during progressive pace treadmill racewalking 
 in the fatigue state .
furthermore , in order to correspond with the progressive paces set on 
 the treadmill , the maximum medial / lateral rotation of the forefoot increased to compensate 
 for tiredness , and this could lead to prolonged pronation / supination of the subtalar joint 
 and could be a potential factor for lower extremity injuries .
the foot is not an isolated 
 section but is part of the body s kinetic chain , which as a linked system of interdependent 
 segments , often engages in interactions to efficiently achieve a desired movement .
the 
 body s kinetic chain is vulnerable to sport fatigue , while long - duration sports always 
 eventually lead to fatigue , especially local muscular fatigue , which can be caused by 
 insufficient energy to conduct a precise workout and increase levels of discomfort . 

insufficient recovery or abnormal neuromuscular control of the foot and ankle during 
 progressive pace treadmill racewalking in the fatigue state , particularly in the subtalar 
 joint , is a primary contributor to inefficient alignment to burdened foot and ankle .
as the 
 forefoot turns inward / outward ( medial / lateral rotation ) excessively in the horizontal plane , 
 the angles of the knees , hips , and back rotation are affected , throwing them out of 
 alignment .
furthermore , it can be concluded that in the excessive medial / lateral rotation 
 forefoot , the extension of the first metatarsophalangeal joint may be ineffective .
when 
 athletes and coaches address problems with the knees , hips , and backs , solutions may be 
 found in the foot .
currently , the physical therapists should assist racewalkers for public 
 health or competitiveness to reduce injuries for the development of lower extremity overuse 
 and increase performance by providing knowledge surrounding efficient gait biomechanics 
 model in the fatigue state after exercise training load .
further studies should be performed 
 to explain the features of biomechanics disorders of the lower extremities and to design 
 therapy programs .
 [ purpose ] the aim of this study was to measure the changes in forefoot maximum 
 medial / lateral rotation in the horizontal plane during progressive pace barefoot 
 racewalking on a treadmill after a physically demanding aerobic exercise load ( a fatigue 
 protocol ) . [ subjects ] eleven junior racewalking men participated in this study . 
 [ methods ] 
 to identify changes in forefoot maximum medial / lateral rotation in the horizontal plane 
 after physically demanding aerobic exercise load , an 8 ch wireless motion recorder 
 ( mvp - rf8-bc ) was utilized . [ results ] forefoot maximum medial / lateral rotation in the 
 horizontal plane 
 was significantly associated with increased paces during progressive pace 
 treadmill racewalking . 
 significant increases in forefoot maximum medial / lateral rotation 
 were observed during progressive pace barefoot racewalking on the instrumented treadmill 
 at 8  km / h and 10  km / h after a physically demanding aerobic exercise load . 
 [ conclusion ] the 
 findings of this study indicated that forefoot maximum medial / lateral rotation increased 
 during progressive pace barefoot racewalking in the fatigue state after a physically 
 demanding aerobic exercise load , which implies that the kinematic features of the forefoot 
 are changed in the fatigue state . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION