Isokinetic Strength Cybex NORM (Cybex International, Inc, Ronkonkoma, New York, U.S.A.) was employed to evaluate isokinetic muscle strength before and after training. Tests were conducted in two different motion modes which included the flexor/extensor and the internal /external rotator. In the former, the range of motion was set in the range of 0-90°. Maximal concentric force had been performed for five times at the angular velocity of 60°, 120° and 180° per second, respectively. Peak torque was taken to represent muscle strength. Only smooth and similar curves with a peak torque which was no less than 90% of the maximum would be taken. The assessment of isokinetic strength of internal/external rotator was generally similar to flexor/extensor. The ankle joint was fixed into 30° dorsiflexion with an air-stirrup ankle brace (Aircast, Summit, NJ) to limit unnecessary inversion/eversion movement, which might affect measurement of knee joint rotation. In addition, the knee and hip joints were kept in 90°, and the range of motion of knee rotation was set in the range between 25° internally and 35° externally.