the latissimus dorsi and gluteus maximus muscles are linked obliquely to the posterior 
 spine by the thoracolumbar fascia , and this is referred to as the posterior oblique sling 
 system1 .
when walking , the muscles of 
 the posterior oblique sling provide trunk stability for extension and work together to help 
 deliver power from the lower body to the upper body .
in addition , they are necessary for 
 trunk stability for rotation and for promoting a mutual gait pattern between the upper and 
 lower extremities2 . moreover , the 
 contralateral gluteus maximus and latissimus dorsi are connected functionally via the 
 thoracolumbar fascia .
therefore , they contract together not only while running , but also 
 during gait and axial movement of the trunk1 , 3 .
the muscles of the posterior oblique sling 
 are essential for promoting mutual gait patterns involving trunk stability and the lower and 
 upper extremities .
they also create joint contraction , not only in running but also in 
 turning the trunk and in walking4 , 5 .
it has also been suggested that the 
 increased gait speed increases the angle of arm swing6 .
however , few studies have examined the effect of a change in arm 
 swing with gait speed on the activities of the latissimus dorsi and gluteus maximus via the 
 posterior oblique sling system . therefore , this study examined the effect of arm swing at 
 different gait speeds in terms of improvement of both gait function and indirect lower 
 extremity muscle activity via the posterior oblique sling system , as it relates to the 
 latissimus dorsi and gluteus maximus .
the subjects of this study were 14 young adult males who voluntarily consented to 
 participate in the study and had no history of disease or any problem with walking .
their 
 average age , height and weight were 28.36  4.31  years , 174.84  6.6  cm and 74.52  7.9  kg , 
 respectively .
surface emg was used to collect raw emg data using a trigno wireless system 
 ( delsys , boston , ma , usa ) .
the sampling rate of the emg signal was 2,000 samples / s using a 
 band - pass of 20450  hz .
two surface electrodes 
 were placed on following muscles : the left ( nondominant side ) latissimus dorsi ( lateral to 
 the t9 spinous process over the muscle belly ) and right ( dominant side ) gluteus maximus ( the 
 midpoint of a line running from the last sacral vertebrae to the greater trochanter)7 .
emg data were normalized using the maximum 
 voluntary isometric contraction ( mvic ) of each muscle measured using the manual muscle test 
 as described by kendall et al8 .
all 
 subjects walked on a treadmill at speeds of 1.5  km / h , 3.5  km / h , and 5.5  km / h for 30 seconds . 

the left latissimus dorsi , and right gluteus maximus muscle 
 activities were measured in subject while walking on the treadmill .
the emg signal was 
 collected for 30 seconds , and the first and last 5 seconds were discarded .
the data were 
 analyzed using one - way repeated - measures analysis of variance ( anova ) .
all 
 significance levels were p<0.05 , and spss version 20.0 ( ibm , armonk , ny , usa ) was used 
 for the statistical analyses .
there was a significant increase in latissimus dorsi muscle activity with a treadmill speed 
 of 5.5  km / h compared with 1.5  km / h and 3.5  km / h ( p<0.05 ) .
the gluteus maximus muscle 
 activity significantly increased in the order of 1.5  km / h < 3.5  km / h < 5.5  km / h 
 ( p<0.05 ) ( table 1table 1 .
comparison of normalized emg data of the two muscles at each treadmill 
 speedmusclesmean  sd ( % mvc)1.5  km / h3.5  km / h5.5  km / hlatissimus dorsi9.4  5.111.1  6.913.3
this study investigated the changes in the activities of the latissimus dorsi and gluteus 
 maximus muscles , as related to the posterior oblique sling system , with changing gait speed . 

a study of children with cerebral palsy showed that 
 increased arm swing is significantly related to gait speed9 .
in addition , ford et al . suggested that rotation of the trunk and 
 pelvis is decreased when arm swing is limited and that gait speed increases due to increased 
 cooperation between the upper and lower extremities when there is no limitation10 .
consequently , it turns out that the 
 change of angle in arm swing due to increased speed affects gluteus maximus and latissimus 
 dorsi activity via the posterior oblique sling system during walking .
one study in which one 
 or both arms were limited suggested that the maximum gait speed was decreased , stride 
 frequency was increased , and stride length was decreased11 .
this means that arm swing during walking can affect the movement 
 of the lower extremity , which is similar to our result , suggesting that muscle activity in 
 the upper extremity can affect that of the lower extremity as arm swing increases .
these 
 results indicate that arm swing connected to increasing gait speed influences lower limb 
 muscle activity via the posterior oblique sling system .
   [ purpose ] this study investigated the effect of different gait speeds on the muscle 
 activities of the latissimus dorsi and gluteus maximus muscles in relation to the 
 posterior oblique sling system . 
 [ subjects ] we recruited 14 young adult males . [ methods ] we 
 measured the left latissimus dorsi muscle activity and right gluteus maximus muscle 
 activity of all subjects while they walked on a treadmill at speeds of 1.5  km / h , 3.5  km / h 
 and 5.5  km / h . [ results ] there was a significant increase in latissimus dorsi muscle 
 activity with a treadmill speed of 5.5  km / h compared with 1.5  km / h and 3.5  km / h . 
 the 
 gluteus maximus muscle activity significantly increased in the order of 1.5  km / h < 
 3.5  km / h < 5.5  km / h . 
 [ conclusion ] the present results indicate that arm swing connected 
 to increasing gait speed influences the muscle activity of the lower limbs through the 
 posterior oblique sling system . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION