It is important to reveal the biomechanical responses of connective tissue to the physical activity,especially for the intensive exercise.The purpose of this work is to investigate the histologic,radiographical and biomechanical responses of connective tissues to intensive physical activity.Rabbits put in an electric cage with high voltage,which made the animals jump and run for 360 times daily.Along with exercise,the X-ray pictures of rabbit tibiae were taken weekly,and the histologic changes of tibiae,insertions of Achilles tendon were examined.The mechanical properties of tibiae under three bending test and biomechanical properties of Achilles tendon,flexor digitorum profundus and medial collateral ligament of the knee under axial loading were determined at 4,21,42 days of exercise.The observations of radiography revealed that a lot of periosteitis of tibia e occured in the early stage of exercise,and these periosteal reactions developed into the new bone tissues at 21,42 days of exercise,so the sectional area of tibiae increased and the tibiae can bear a more heavy burden.The results of biomechanical testS of soft tissues showed that the failure loads,linear loads and energy absorptions increased followed 4,21,42 days of execrcise.These observations indicated that the connective tissues can adapt to the intensive exercise according to Wollflaw.The increase of mechanical properties of connective tissues are benificial for the athletes to prevent sports injuries in physical trainings and competitions.