the symmetry of gait refers to the shift and support of body weight on both sides of the 
 lower extremities , and it requires external stability of the hip joint . external stability 
 is the ability to control the center of mass of body weight while moving the body1 . during the stance phase of gait , the 
 posture of the hip joints is stabilized and the gluteus medius , which is the hip abductor 
 muscle in the hip joint , plays an important role in independent gait and balance 
 recovery2 . muscle weakness and 
 malfunction of the gluteus medius is related to various musculoskeletal disorders , including 
 low back pain3 , 4 , while height differences in the hip joint can be found in persons 
 with radiating pain around the low back and hip joints , which is accompanied by muscle 
 weakness in the gluteus medius5 . vleeming 
 et al.6 suggested that a posterior oblique 
 sling links the hamstring , gluteus maximus , thoracolumbar fascia , and contralateral 
 latissimus dorsi , in sequence . lee et al.7 
 studied the changes in muscle activity of the gluteus medius in the stance phase as vertical 
 load was applied to the lower extremities in the swing phase . they found that muscle 
 activity increased when 0.5  kg of vertical load was applied to the lower extremities in the 
 swing phase compared to normal gait , whereas counterintuitively the muscle activity 
 decreased when 1  kg of vertical load was applied , comparied to the 0.5  kg load . in addition , 
 they noted that among loads of 0 , 1 and 2% of body weight , the most appropriate weight for 
 strengthening the gluteus medius was a vertical load of 1% of body weight8 . furthermore , jung et al.9 measured the muscle activity in the gluteus 
 medius during walking on a treadmill set at angles of 0 , 5 , and 10 , and they showed that 
 the muscle activity was the highest at when the treadmill angle was 5. these previous 
 studies discussed muscle activity of the gluteus medius in relation to vertical loads and 
 treadmill angles , which are intervention conditions whose outcomes are thought to be 
 affected by gait speed . therefore , the present study aimed to determine the changes in the 
 muscle activities of the gluteus medius , latissimus dorsi , and gluteus maximus at different 
 gait speeds , to collect basic data for the study of the gluteus medius . the subjects of this study were 18 young and healthy male adults whose mean age , height , 
 and weight were 26.4  years , 173.37  cm , and 72.5  kg , respectively . the subjects had no 
 history of functional impairment in their musculoskeletal or nervous systems and they had no 
 difficulty with normal gait . the subjects fully understood the experimental method before the 
 experiment started and they participated in the experiment voluntarily . in addition , none of 
 the processes in this study were harmful to the human body and all the subjects read and 
 signed a written consent form . electromyography ( emg ) was used to measure the maximum 
 voluntary isometric contraction ( mvic ) . the mvic activities of the gluteus medius , 
 latissimus dorsi , and gluteus maximus were measured three times and then averaged . then , the 
 subjects walked on a treadmill at gait speeds of 1.5 m / s , 2.5 m / s , and 3.5 m / s while the 
 muscle activities of each muscle were measured . a mp36 ( biopac system inc . , usa ) was 
 employed to collect emg data of the latissimus dorsi , the gluteus medius , and the gluteus 
 maximus . while subjects walked at the three different gait speeds , the emg signals were 
 collected for 20 seconds out of 30 seconds , the first and last five seconds being discarded . 
 for each emg measurement , the subjects performed gait on the treadmill for one minute under 
 the same conditions and measurements were taken during the last 30 seconds of gait . the 
 subjects walked barefoot and they removed all the outer clothing they were wearing on the 
 upper portion of their body , retaining only their undershirts . the electrodes were placed 
 horizontally in the direction of the muscle fibers at 4  cm below the inferior angle of the 
 scapula in the middle area between the outermost end of the trunk and the vertebrae for the 
 latissimus dorsi . the electrodes were placed horizontally in the direction of the muscle 
 fibers at one third the distance between the greater trochanter of the femur and the second 
 sacrum for the gluteus maximus , and for the gluteus medius the electrodes were placed 
 horizontally in the direction of the muscle fibers at one third the distance between the 
 iliac crest and the greater trochanter . one - way analysis of variance was used to examine the 
 pelvic muscle activities during gait . as a post hoc test a comparison of the results of the pelvic muscle activities at the under various gait 
 speeds found that the latissimus dorsi showed a significant increase in muscle activity when 
 performing a faster than normal gait , while the gluteus medius showed no significant 
 difference in muscle activities among the different gait speeds . the gluteus maximus showed 
 increases in muscle activity when performing gait at speeds faster than the normal gait 
 speed ( 1.5 m / s ) ( table 1table 1.comparison of the muscle activities at the different gait speeds ( unit : 
 % mvic)1.5 m / s2.5 m / s3.5 m / sgmed11.573.5010.883.569.863.14ld*2.741.163.181.344.251.77gmax*10.382.5411.472.4212.532.42*p<0.05 , meansd . gmed : gluteus medius , ld : latissimus dorsi , gmax : gluteus 
 maximus . significant difference between 1.5 m / s and 3.5 m / s ( p<0.05 ) . significant difference between 2.5 m / s and 3.5 m / s ( p<0.05 ) . significant difference between 1.5 m / s and 3.5 m / s ( p<0.05 ) . ) . gmed : gluteus medius , ld : latissimus dorsi , gmax : gluteus 
 maximus . significant difference between 1.5 m / s and 3.5 m / s ( p<0.05 ) . significant difference between 2.5 m / s and 3.5 m / s ( p<0.05 ) . significant difference between 1.5 m / s and 3.5 m / s ( p<0.05 ) . a social and functional gait , such as crossing the road safely , requires a speed of 1.11.5 
 m / s on average10 . this study aimed to 
 determine changes in muscle activity of the gluteus medius at gait speeds faster than a 
 normal gait speed . although a number of studies have been conducted to determine changes in 
 the muscle activity of the gluteus medius across different intervention methods used to 
 strengthen the gluteus medius , few studies have been conducted on the changes in muscle 
 activity of the gluteus medius with gait speed . the gluteus medius is a muscle that prevents 
 the pelvis from descending on the opposite side to the leg in the swing phase during 
 walking . in previous studies , this muscle was selectively strengthened by applying weight to 
 the legs or changing the angle of treadmills . our present study s results show that gait speed has no effect on the 
 selective strengthening of the gluteus medius . the study conducted by sin et al.11 also noted that no change in the muscle 
 activity of the gluteus medius was found between gait speeds changes of 3.5 and 5.5 m / s . in 
 particular , while performing gait with weight loading on the arm , changes in the muscle 
 activities of the latissimus dorsi and the gluteus maximus , which are the principal muscles 
 of the posterior oblique sling theory proposed by bermark12 , were found to be significant , but no change in the muscle activity 
 of the gluteus medius was found . in summary , at faster gait speeds , greater increases in the 
 muscle activities of the latissimus dorsi and the gluteus maximus are seen , whereas no 
 correlation has been found between gait speed and the muscle activity of the gluteus medius . 
 in this study , we measured the muscle activity of the gluteus medius , at a normal gait 
 speed , and at gait speeds faster than that normally used in ordinary daily living . therefore , intervention methods that aim to selectively strengthen the gluteus medius in 
 order to establish external provide stability of the pelvis during walking , using weight 
 loading or sloped treadmills are an effective intervention methods , but changing the gait 
 speed has no significant effect on the selective strengthening of the gluteus medius .
[ purpose ] the present study aimed to determine the changes in the muscle activities of 
 the gluteus medius , latissimus dorsi , and gluteus maximus at different gait speeds , to 
 collect basic data for the study of the gluteus medius . 
 [ subjects and methods ] the 
 subjects were 18 young and healthy male adults whose mean age , height , and weight were 
 26.4  years , 173.37  cm , and 72.5  kg , respectively . 
 electromyograpy was used to measure the 
 maximum voluntary isometric contraction of each muscle three times and the values 
 averaged . 
 then , the subjects walked on a treadmill at gait speeds of 1.5 m / s , 2.5 m / s , and 
 3.5 m / s and the muscle activity of each muscle was measured . 
 [ results ] the gluteus medius 
 showed no significant difference in muscle activity among the different gait speeds . 
 [ conclusion ] for selectively strengthening the gluteus medius , to establish the external 
 stability of the pelvis during walking , weight loading or sloped treadmills are effective 
 interventions . 
 however , different gait speeds exert no significant effect on the selective 
 strengthening of the gluteus medius .