RT Journal Article
SR Electronic
T1 Dependence of human maximum vertical counter-movement jump height on activation sequence of the biarticular muscles
JF British Journal of Sports Medicine
JO Br J Sports Med
FD BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine
SP 538
OP 539
DO 10.1136/bjsm.2011.084558.16
VO 45
IS 6
A1 M Bračič
A1 M Supej
A1 Z Matjačić
YR 2011
UL http://bjsm.bmj.com/content/45/6/538.3.abstract
AB Background When executing vertical jumps a noticeable problem transpires in the efficient transfer of rotational energies of the trunk and the lower body segments into the largest possible vertical velocity. In the transfer of energy, the biarticular muscles rectus femoris (RF) and gastrocnemius (GAS) play an important (Bobbert & Van Ingen Schenau, 19881; Gregoire et al., 19842). Objective The hypothesis of the study were that athletes with greater maximum vertical counter movement jump height have better energy efficiency of two-legged jumps due to correct activation sequence of the biarticular muscles RF and GAS, which ensure a transfer of rotational kinetic energy between body segments following a proximal to distal principle. Setting and participants 12 male elite athletes (age: 22.41±3.39 years; height 177.58±6.86 cm, body mass 74.92±5.23 kg) performed two-leg counter movement jumps (CMJ). Methods Eight camcorders with a frequency of 200 Hz were used for the 3D kinematic measurements of CMJ. The ground reaction forces of jumps were measured unilaterally and bilaterally using two independent and synchronized force platforms. The maximal jump height of the centre of body's mass (HCM) was determined by the time integration (tfl) of the vertical force (F=Fz-mg) signal: HCM=tfl2•g•8–1. Electromyographical data of the time to peak EMG (TTPEMG) from biarticular RF and GAS in concentric phase of the jump were analyzed. Results The comparison between two groups showed that athletes with greater maximum vertical counter movement jump height (group_1: 64.10±5.08 cm vs group_2: 56.41±3.88 cm; p<0.05) have different activation sequence of the biarticular RF and GAS (group_1; TTPEMG_RF=110.53±20.11 ms, TTPEMG_GAS=137.88±22.43 ms vs group_2; TTPEMG_RF=143.56 ±32.23 ms, TTPEMG_GAS=84.81±25.67 ms; p<0.05) which indirectly implicate that the transfer of rotational kinetic energy between body segments follows a proximal to distal principle. Conclusions It is concluded that correct activation sequence of the RF and GAS is essential in the execution of vertical counter movement jump.