Effects of perturbation training on quadriceps and hamstring electromyographic ratios

It seems knee joint stability through co-contraction (CC) of hamstrings and quadriceps may be necessary for athletes with quadriceps dominance (QD) neuromuscular deficit. The lower CC and muscle activity ratio in medial compartment of knee can predispose this joint to excessive valgus position that exaggerates anterior cruciate ligament (ACL) injury. The purpose of this study was to determine the effects of perturbation training on quadriceps and hamstring ratios in QD deficit athletes. EMG data of quadriceps and hamstrings (during single limb drop landing) of 53 (26 control and 27 experimental) athletes with quadriceps dominance deficit (identified with tuck jump test) acquired in pre-test and post-test. After completing 6 weeks of perturbation training in experimental group, the repeated-measures analyses of variance, independent sample t-test and paired sample t tests used for statistical analysis. After perturbation training, the lateral knee compartment CC decreased and medial knee compartment CC increased (both in feed-forward and feedback phases). The medial to lateral knee compartment ration increased after six weeks of perturbation training. Also in the post test, the higher effect size observed in studied variables. Improvement in CC in knee medial compartment can limit the knee valgus and also anterior shear force that led to ACL optimal control. Considering the extremely large effect size of the perturbation group, we recommend that this program be used in the correction of QD deficit women in future.