BACKGROUND:The creep performance of bone tissues during exercise is achieved through the microstrain,and the holosteous torsion can completely retiect the biomechanicel charactedstics of bone tissues.OBJECTIVE:To determine the creep characteristics of rabbit tibia under the torsion load following exercise.DESIGN,TIME AND SETTING:A parallel controlled animal observational experiment was performed at the Laboratory of Biomechanics in Orthopedic Hospital of Sichuan Province between May 2005 and July 2007.MATERIALS:A total of 32 Japanese white rabbits,irrespective of genders,aged 6 months,were divided into exercise group(n=24)and control group(n=8).METHODS:Exercise group animals were placed in cage to receive electrical stimulus.0.1-0.2seconds once every 20 seconds.Following the stimulation,the animals ran and jumped for several paces along with the cage and made a tum,15 minutes once,three times per day,totally 45 minutes,at the interval of 15 minutes.The exercise was carried out five days per week for 4successive weeks.The control group was fed as exercise group.but received no exercise.MAIN OUTCOME MEASURES:After 4 week exercise.the tibias were griped by the torsion clamping apparatus,the creep characterizes of anterior,posterior,medial and lateral sides of tibia under 0.52 N·m torsion load within 500 seconds were determined by strain gauge technique.RESULTS:Under torsion load,the creeps were present obviously in the rabbit tibia,reached the creep curve inflection point at 2seconds,and then gradually appeared.After 4 weeks,the creeps of tibias at anterior and posterior side in the exercise group were less than control group;in the control group,the anterior side of tibia was remarkably greater than the medial side.After exercise.the creep was the smallest in anterior side,which was less than the lateral side(P＜0.05).CONCLUSlON:The creep characteristics of tibia are anisotropic,the deformation at the anterior and posterior sides is greater than that at the medial and lateral sides.Exercisecan alter the creep charactedstice of rabbit tibia and reduces the creep at the anterior and posterior sides.