kumar1 claimed that people have 
 difficulty using the hamstrings , muscles that are prone to shortening .
ayala2 argued that the hamstrings play a 
 significant role in effective walking and running , and that short hamstrings have often been 
 observed in people , especially athletes . in addition , extended hamstring muscle contraction 
 prevents complete extension and reduces flexibility . as stated by kim3 ,
stretching is one of the most popular methods to increase 
 muscular flexibility ; thus , self - myofascial release with a foam roller has gradually become 
 preferred to improve muscular flexibility , particularly since it is a low - cost intervention . 

faulkner4 also asserted that 
 self - myofascial stretching improves one s sense of physical awareness and joint sensitivity , 
 and improves the function of the proprioceptors , which function in balance and motor skills . 

muscular flexibility of the hamstrings can be examined using the sit and reach test , 
 passive toe touch test , and straight leg raise ( slr test ) .
the sit and reach test is highly 
 reliable ; thus , it is used as a valid testing method5 , 
 6 .
ultrasound delivers heat deep into 
 the muscles , resulting in better flexibility of the collagen fibers and muscles7 , 8 . 

the therapeutic effects of ultrasound include relaxed joint contracture , better adhesion , 
 and reduced joint stiffness , pain , and muscular rigidity7 , 9 .
therefore , this study explored the positive effects of self - myofascial release on hamstring 
 muscular flexibility and proprioception and investigated the comparative effectiveness of 
 the stretch combined with therapeutic ultrasound .
this study involved 30 university students ( mean age , 21.8  0.81  years ; 1:1 male : female 
 ratio ; mean height , 167.6  8.49  cm ; mean weight , 62.5  8.13  kg ) with no history of pain in 
 the achilles tendon or hamstrings within the most recent 6 months . written informed consent 
 was obtained from each subject .
this study was approved by the ethics committee of the kaya 
 university ( kaya irb-78 ) .
the subjects participated in two experiments . in the first experiment ( ms ) , they performed 
 self - myofascial stretching using a foam roller daily for 1 week . in the second experiment 
 ( msu ) , the same participants performed the self - myofascial stretching after the 15-minute 
 application of ultrasound .
ultrasound therapy were applied to the biceps femoris , 
 semitendinosus , and semimembranosus muscles for 5 minutes each ( frequency , 1  hz ; strength , 
 3  w / cm ; velocity : 2  cm / sec ) . this study included pre- and post - tests of 
 hamstring muscle flexibility and hip joint proprioception .
this study used the sit and reach test to 
 evaluate hamstring flexibility , while dual inclinometers were used to test hip joint 
 proprioception .
a paired t - test was used to test differences between the pre- and post - test 
 results , while an independent t - test was used to test differences between the two 
 experiments .
the use of self - myofascial stretching in the ms experiment had a significant effect on 
 hamstring flexibility and hip joint proprioception . however , the addition of ultrasound to 
 self - myofascial stretching in the msu experiment had no additive effect ( table 1table 1.comparison of hamstring flexibility and hip joint proprioception before versus 
 after the ms and msu interventionsbeforeafterdifferencesmssrt ( cm)7.42  10.2110.92  9.84 * 9.58  10.12jps ( degrees)3.57  2.491.41  1.30 * 0.40  1.02msusrt ( cm)5.42  11.3310.67  9.73 * 9.36  10.48jps ( degrees)7.45  4.281.37  2.12 * 0.79  1.82ms : self - myofascial stretching ; msu : self - myofascial stretching with ultrasound ; srt : 
 sit and reach test ; jps : joint position sense ( * p<0.05 , mean  sd ) ) .
ms : self - myofascial stretching ; msu : self - myofascial stretching with ultrasound ; srt : 
 sit and reach test ; jps : joint position sense ( * p<0.05 , mean  sd )
as suggested by sherer11 , 
 self - myofascial stretching had a significant effect on increased hamstring flexibility and 
 improving hip joint proprioception .
longo12 also investigated the muscle and tendon stiffness after stretching 
 with feet lifted 20 degrees toward the shin , that is , in dorsi - flexion , using an 
 electromyogram and an ultrasound .
as shown in the aforementioned research , this study also 
 presented the same result that self - myofascial stretching using a foam roller immediately 
 increased hamstring flexibility and enhanced hip joint proprioception .
however , the results of this study showed that the use of therapeutic ultrasound for 15 
 minutes prior to the self - myofascial stretching had no additional effect on hamstring 
 flexibility or hip joint proprioception .
therapeutic ultrasound delivers heat to the soft 
 tissues , which helps increase blood circulation and induce relaxation .
as suggested by 
 kondo13 , the application of heat on leg 
 contractures in mice did not increase muscular flexibility .
however , further research should 
 be performed since lounsberry14 presented 
 the contradictory result that therapeutic ultrasound treatment applied to the hamstrings can 
 increase muscular flexibility . the current study concluded that self - myofascial stretching immediately increased hamstring 
 flexibility and improved hip joint proprioception but that the addition of therapeutic 
 ultrasound offered no further benefit .
 [ purpose ] this research explored the positive effects of self - myofascial release on 
 hamstring muscular flexibility and proprioception and investigated the effectiveness of 
 the stretch combined with therapeutic ultrasound . [ subjects and methods ] this study 
 included 30 healthy university students with no history of pain in the achilles tendon or 
 hamstring within the recent 6 months . 
 each participant completed two experiments . in the 
 first experiment ( ms ) , they completed self - myofascial stretching using a foam roller for 7 
 days . in the second experiment ( msu ) , the same participants performed the self - myofascial 
 stretching after the 15-minute application of ultrasound . 
 this study involved a pre- and 
 post - test on hamstring muscle flexibility and hip joint proprioception . 
 [ results ] the use 
 of self - myofascial stretching in the ms experiment had a significant effect on hamstring 
 muscle flexibility and hip joint proprioception . 
 however , the addition of ultrasound in 
 the msu experiment had no additive effect . [ conclusion ] self - myofascial stretching 
 immediately increased hamstring muscle flexibility and improved hip joint proprioception , 
 but the addition of pre - stretch ultra sound provided no further benefit . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION