Abstract
ACL injuries are associated with a high risk of developing knee osteoarthritis in the future. In the landing motion, which is the most common injury movement, it is recommended that the vertical component of floor reaction force be lowered by landing softly to reduce the load on the knee joint. However, muscle contraction also affects joint loading, and especially in rapid deceleration movements such as landing, co-contraction of antagonist muscles is likely to occur, but joint loading has not been discussed due to differences in the magnitude of co-contraction depending on the landing method. In this study, one-leg landing movements (comfortable landing, soft landing, and stiff landing) from the 200 mm platform were measured in 11 healthy male subjects. The shock absorption capacity (loading rate) and quadriceps and hamstrings co-contraction index (CCI) were compared, and the relationship between CCI and loading rate was analyzed. The results showed that soft landing resulted in significantly smaller loading rate and CCI compared to other landing methods. In addition, the relationship between loading rate and CCI was shown to increase as CCI increased regardless of the landing method. These results suggest that reducing the co-contraction of the quadriceps and hamstrings improves shock absorption capacity, confirming the usefulness of landing softly to reduce the burden on the knee joint.
https://ror.org/03e1t0653 
