Kinematic and kinetic differences in the execution of vertical jumps between people with good and poor ankle joint dorsiflexion (vol 31, pg 1789, 2013)

The aim of the present study was to investigate the kinematic and kinetic differences in the execution of vertical jumps between individuals with good and poor ankle dorsiflexion. Fifteen physical education students were assigned to the flexible group (FG), while another 15 were assigned to the inflexible group (IFG). The two groups executed countermovement jumps (CMJ) and drop jumps from a 60 cm height (DJ60). For the CMJ, the FG jumped higher (32.0 +/- 4.0 cm vs. 30.2 +/- 4.9 cm, P = 0.27) and used a greater range of motion in all leg joints. The IFG jumpers raised their heels off the ground and had a greater horizontal distance between the centre of mass of the trunk and the centre of the hip joint (L-CMh 25.6 +/- 3.4 cm vs. 30.9 +/- 4.3 cm, P < 0.001). In the DJ60 the FG jumped higher (22.4 +/- 5.9 cm vs. 19.5 +/- 4.6 cm, P = 0.14) with a greater vertical shift of the body centre of mass (BCM) (S = 0.45 +/- 0.11 cm vs. 0.36 +/- 0.05 cm, P < 0.01) and better joint coordination. The IFG jumpers changed the position of their trunk and heels depending on the jump type. Trainers should reconsider the technical issues of vertical jumps according to the flexibility of the ankle joint.