Effects of a 4-week plyometric training on activity patterns during different phases of one-leg drop jump with focus on jump height.

Athletic women have shown a higher risk of ACL injury during jump landing compared to men. Plyometric training can be an alternative way to minimize the risk of knee injuries via the changed muscle activity patterns. Hence, the aim of this study was to determine the effects of a 4-week plyometric training program on the muscle activity pattern in different phases of one-leg drop jump in active girls. Active girls were randomly allocated into 2 groups (Plyometric training = 10, Control group = 10) where the plyometric training group (PTG) performed 60 min exercises, 2 sessions/1 week for 4 weeks while the control group (CG) had their daily activity. In the pre to post test, the sEMG was recorded from the Rectus Femoris (RF), Biceps Femoris (BF), Medial Gastrocnemius (GaM), and Tibialis Anterior (TA) muscles of the dominant leg during the Preparatory phase (PP), Contact Phase (CP), Flight Phase (FP) of one-leg drop jump. Electromyography variables (Signal amplitude, Maximum activity, Time to peak (TTP), Onset and activity time and Order muscle activity) and Ergo jump variables (Time of preparatory phase (TPP), Time of contact phase (TCP), Time of flight (jump height) phase (TFP), and Explosive power were analyzed. The Univariate ANCOVA test showed a significant difference between the two groups in Activity Time, whilst adjusting for pre-test as a Covariate, only in TA muscle (F = 5.09, p = 0.038, η = 0.230). In PTG. TA (- 15%), GaM (- 19%), and BF muscles (- 9%) started their activity earlier while there was no significant difference between the two groups at the Onset time. TTP of RF was significantly different between the 2 groups only in the PR phase (0.216 ± 0.07 vs 0.153 ± 0.09 s) (p = 0.049, 95% CI = 0.001, 0.127). Results of the present study suggest that a 4-week plyometric training can improve the stability of leg joints via earlier recruitment of muscles and change activity patterns in lower limb muscles. It also recommends that the preparatory phase before landing be considered an important stage in preventing sports injuries in a training program.