Comparative Study On Biomechanics Characteristics Of Three Plyometric Jump Techniques

Purpose:By means of sports practice, it was well-known that the plyometric jump training can improve the power strength in lower extremities, and the more effects will be received with the combined training than the single muscular training. The purpose of this study was to explore the kinematics, kinetics, and electromyography characteristics of countermovement jump, squat jump, and counter jump with arm swing and found out the differences in power strength among three plyometric jumps, further found out their biomechanical mechanism and offered some proposal on lower extremities training for coaches.Methods:Ten volleyball players with rank 2 certificate voluntarily participated in this study. High-speed cameras (JVC9800, Japan), multi-dimension force plate(JP6060, China),8-channel sMEG (JE-TB0810, China) were used in this study. Synchronization Testing have been carried out on countermovement(CMJ), squat jump (SJ), and counter jump with arm swing(CJA). The relevant parameters were acquired.Results:l)Among three plyometric jumps, the time of squat period, pedaling and stretching period, and the height of CG were SJ<CMJ<CJA;the maximal reaction force of ground during takeoff phase were SJ<CMJ, and CJA<SJ,2) rectus femoris and biceps femoris muscle were the main muscles during the takeoff phase, the average amplitude of Semg of both muscles have the same traits:the largest amplitude was showed during squat phase, the smallest during the braking phase, and the largest during the pedaling and stretching phase;the amplitude of sEMG of vastus medialis and vastus lateralis had the gradually increased trend till the largest at the pedaling and stretching phase; the amplitudes of sENG of anterior tibial muscle were the stablest muscle during squat, braking, and pedaling and stretching phase, the largest amplitude of sEMG of medial gastrocnemius was only showed during squat phase,3) the agular of velocities of hip, knee, and ankle joints gradually increased from squat to pedaling and stretching phase during takeoff phase in three plyometric jumps, the results were as follows:hip joint:CMJ>CJA>SJ; knee joint:CMJ>SJ, CMJ>CJA, ankle joint:CJA>CMJ>SJ, and 4) the torque of hip, knee, and ankle joints gradually decreased during takeoff phase in three plyometric jumps, the results were as follows:hip joint:CMJ<SJ, CJA<SJ; knee joint:SJ<CMJ, SKCJA; ankle joint:CMJ<SJ, CJA<SJ.Conclusion:The work of CMJ was higher than that of SJ in lower extremities, and CJA was higher than SJ; the reason was that the arm swing or counter movement increased the work output of lower extremities, and it therefore was the main factor in affecting the height of jump. Counter movement and arm swing produced different joint torques, it means that these two techniques have different plyometric effects on the work output of lower extremities. As a consequence, It is very important for athletes to adopted different plyometric jumps techniques in training or competition.