A comparison of lower-body flexibility, strengths and knee stability between karate athletes and active controls

Probst, M.M., R. Fletcher, and D.S. Seelig. A comparison of lower-body flexibility, strength, and knee stability between karate athletes and active controls. J. Strength Cond. Res. 21(2):451-155. 2007. - The purposes of this study were to compare the lower-body flexibility, strength, and knee stability of karate athletes against that of non-karate controls and to determine whether regular karate training results in adaptations that may result in an increased risk for knee injury. Flexibility measurements included knee flexion and extension, hip flexion and extension, hip internal and external rotation, and foot inversion and eversion. Nine karate athletes (4 women and 5 men, age = 24.3 +/- 6.7 years) and 15 active, non-karate controls (7 women and 8 men, age = 22.1 +/- 3.2 years) participated. No subjects reported recent knee surgery or chronic or acute knee pain. Concentric quadriceps and hamstrings strength and endurance were measured using a Biodex II isokinetic dynamometer at 60 degrees center dot s(-1) and 180 degrees center dot s(-1). Eccentric strength was measured at 150 degrees center dot s(-1) and 250 ft-lb (339 N center dot m). Knee stability was measured via varus and valgus stress and anterior drawer testing. Karate athletes demonstrated a significantly greater right hip flexion (p <= 0.05). Isokinetic testing demonstrated a significantly greater concentric right and left hamstrings peak torque at 60 degrees center dot s(-1), right hamstrings to quadriceps torque ratio at both 60 degrees center dot s(-1) and 180 degrees center dot s(-1), and a significantly faster time to peak torque in the hamstrings at 60 degrees center dot s(-1) in the karate athletes (p <= 0.05). Eccentric isokinetic testing showed a significantly higher peak torque at 60 degrees center dot s(-1) in both the right and left quadriceps and hamstrings in the karate group compared to the controls (p <= 0.05). There were no significant differences in bilateral movement of the knees between the karate and control groups. The results indicate that this group of karate athletes may have demonstrated sport-specific adaptations in certain flexibility and strength measurements, but they showed no increased risk for knee injury.