ABSTRACT

　We examined the influence of Jack-knife stretching on lower limb muscle tightnessand kicking motion in adolescent soccer players. It is hypothesized that performingJack-knife stretching for six months, improves flexibility of the lower extremitymuscles and decreases posterior pelvic tilt during kicking motion. Twenty-two boys （mean age 12.1±1.1 years） belonging to the junior division of the professional soccerteam, were included. Height（ cm）， body weight（ kg）， distance of long seat type bodyanteflexion （cm）， straight leg raising （SLR） （degrees）， heel hip distance （HHD）（mm） and posterior pelvic tilt （degrees） were assessed. Jack-knife stretching wascarried out five times, in the morning and at night, for six months. The height andweight at initial measurement and after six months were 154.0±10.4cm and 45.3±9.3kg, and 158.1±10.1cm and 48.0±9.6kg, respectively. Distance of long seat type bodyanteflexion was 35.5±7.1cm, 42.0±6.0cm（ p = 0.004）．SLR was 64.9±6.8ﾟ, 75.3±7.2（P<0.001）．HHD was 121.5±32.6mm, 111.1±24.9 mm（P=0.008）．Posteriorpelvic tilt during an in-step kick was significantly increased. Jack-knife stretchingimproves the distance of long seat type body anteflexion, SLR and HHD. However,posterior pelvic tilt during an in-step kick was significantly increased.

DECENTE SPORTS SCIENCE Vol.40/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE