Drop jump (DJ)
The main objective of the Drop Jump (DJ) test is to measure the explosive-reactive-ballistic strength of the lower limbs, using the myotatic reflex. The DJ test is part of the Bosco vertical jump test battery to assess the functional, neuromuscular and morphophysiological characteristics of the extensor muscles of the lower limbs.
- Required Material: Plyometric boxes of different heights (usually ranging from 20 to 100 cm). Different measuring instruments can be used for this test, such as force platforms, contact platforms, optical position transducers (infrared), accelerometers, video analysis or even specific software and Apps.
- Procedure: The Drop Jump is a drill that consists of dropping from a plyo box at a certain height, bending the knees to 90º upon contact with the ground, and then, without pause, making a maximum vertical jump. It is not permitted for the participant to jump out of the box instead of simply “dropping”. Nor is it allowed to perform arm swings, since the subject must place his/her hands on the waist-hip during the entire test, thus focusing the action of the lower limbs.
- Assessment: The jump height is measured in centimetres (cm) and the subject has a maximum of 3 attempts. (En Fisicalcoach,) The highest mark obtained by the subject can be recorded, as well as the mean and the median. In addition to jump height, different variables of interest can be recorded depending on the measuring instrument used.
- Remarks: This test demands a much higher level of strength in the subject’s legs, than a standard vertical jump test. This test is also often used to assess the risk of anterior cruciate ligament (ACL) injury.
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