Feedforward and Feedback Function of Selected Lower Limb Muscles Following Plyometric Exercises and Cryotherapy

Purpose: Despite the widespread use of cryotherapy in sports fields there is a lack of certain evidence of its impact of it on muscle activation especially following fatigue-induced exercise. This study aimed to assess the impact of cryotherapy alone and after plyometric exercises on knee muscle activation during the drop jump task. Method: 35 active female subjects (mean age of 22.74±2.10, mean BMI of 20.02±2.55) participated in this quasi-experimental pre and post-test study. There were three experimental groups (20-min cryotherapy (Cr), plyometric (P), and plyometric- cryotherapy (PC)) and one control (Co) group. Muscle activation amplitudes (EMG) of knee muscles (rectus femoris(RF), biceps femoris(BF), tibialis anterior (TA), medial gastrocnemius(MG)) were measured and compared in three phases of the drop jump task (one feedforward pre-activation and tow feedback eccentric and concentric phases). Skin temperature was recorded before and after cooling intervention as well. Repeated measure ANOVA statistical test at a significant level of 0.05 was used for comparisons. Results: results showed that skin temperature was decreased significantly after cryotherapy and maintained for 20 minutes. No significant changes in knee muscles EMG were seen in the feedforward and concentric phase of the drop jump task in any groups (P>0.05). but as fore eccentric phase, RF activation decreased the following cryotherapy immediately and after 20 min (P=0/01) and had a significant difference with Co group (P=0.01), besides MG activation decreased in all Cr, P, PC groups immediately(P=0.01). However, no significant differences were seen between them with the Co group (P>0.05). Conclusion: Considering the present results cryotherapy alone and after fatigue-induced plyometric training had a minor effect on knee muscle activation during a functional jumping movement but the impact of these amount of changes on knee biomechanics is not very clear so further studies are essential for a better conclusion.