Background:The aim of this study is to compare co-contraction patterns, lower extremity muscles onset latencies to time of impact and magnitude of activation of selected muscles
during landing after single-leg-jump in adolescent soccer players with or without lower extremity injury.
Methods:Twenty two players of under sixteen male national soccer team of China, divided into injury group(IG)who had ankle sprains and will return to play and control group(CG) who
had no injuries, volunteered to participate in our study. The SEMG muscle activity order and contribution rate of players’ lower extremities were tested during specific single leg landing.
Results:Compared with CG, the activity of IG were significantly slower on TA (P = 0.0001), BF (P = 0.01), VM (P = 0.0001), VL (P = 0.001), PL (P = 0.0001), TP (P = 0.0001) and ST (P =
0.01), while the activity of RF was faster (P = 0.024). Most tested muscles of both groups had same contribution rate (P> 0.05) during the movement processing which was from heel-landing to toes-off.
But the contribution rate of BF had significant difference between the two groups (P = 0.016).
Conclusions:During stance phase of single leg landing, the leg muscles of healthy elite adolescent soccer players have the corresponding activation order: ankle dorsiflexion,
quadriceps and hamstrings collaborative stable knee and then PL, TP and gastrocnemius muscle collaborative stable ankle; elite adolescent soccer players with lower extremity soft tissue injury before
returning to play had significantly delayed activation of the rectus femoris and compensatory increase of hamstring work; muscle activation order and contribution rates during specific actions can be
used to develop and evaluate the efficacy of targeted rehabilitation programs.