Background: Knee injury commonly happened in badminton players. Their knee strength character is unknown. The aim of this study was to determine and compare the isokinetic strength,
flexion/extension ratio and functional ratio for Shanghai adult badminton players. It provides theoretical basis for knee strength evaluation and injury prevention.
Methods: Seven male and eight female badminton players involved in this study. Isokinetic strength was tested for both knees, their flexion/extension ratio and functional ratio was
compared between male and female. Both male and female plays completed isokinetic strength for both knees at the speed of concentric 60°/s, 300°/s, and eccentric 60°/s. Relative maximal torque
(maximal torque/weight), knee flexion/extension ratio(the ratio of concentric maximal torque of flexion and concentric maximal torque of extension), functional ratio(also named as dynamic control
ratio, the ratio of eccentric knee flexor and knee extensor) were compared.
Results: Male players have higher value for hamstring and quadriceps at concentric 60°/s, and quadriceps for 300°/s than female players（1.86±0.21vs.1.66±0.16, 3.52±0.37vs.3.11±0.40,
2.32±0.24vs. 1.89±0.09, P<0.01. The extensor is significant stronger than flexor. The knee flexion/extension ratio at the speed of 60°/s is 53.1% for male, and 54.1% for female players. The knee
flexion/extension ratio at the speed of 300°/s is 66.3% for male, and 74.0%for female players. The functional ratio of the knee is 56.8% for the male players, and 58.8% for female players.
Conclusion:1. Male players have higher value for hamstring and quadriceps at concentric 60°/s, and quadriceps at 300°/s than female;2. There are no significant differences between
male and female players for both flexion/extension ratio and functional ratio; 3. The flexion/extension ratio of both male and female is relative low. It shows, comparing with quadriceps, the
hamstring is relative low. It could be related with injury, but it still need further research.