Depth jumping can significantly increase power production and vertical jump height…
It’s been established in both Eastern and Western studies that depth jumping, or shock training, can significantly increase power production and vertical jump height. This is mostly due to the following factors:
1. An increase in reactive strength
Reactive strength refers to the capacity to rapidly switch from an eccentric/yielding action to a concentric/overcoming action. Lack of reactive strength will lead to a longer coupling time and, consequently, lower force and power production during the overcoming portion of the movement (Kurz 2001).
2. Neural adaptations
Viitasalo et al. (1998) found a different neural response between athletes doing a lot of jumping and regular individuals when doing a depth jump. Jumpers were able to activate more motor units during the movement (greater EMG) and plan the motor command faster (higher and more rapid pre-action EMG).
Kyröläinen et al. (1991) also found that 16 weeks of depth jump training led to better jumping efficiency. Schmidtbleicher (1987 and 1982) found that trained subjects were able to use the kinetic energy produced during the eccentric portion of a depth jump, while in untrained subjects this eccentric period was actually inhibiting instead of potentiating!
Finally, Walshe et al. (1998) concluded that the superiority of depth jump training over regular jump training was due to “the attainment of a higher active muscle state,” meaning that the fast eccentric portion of the movement increased muscle activation.
3. Structural adaptations
Depth jumps have been reported to cause some muscle soreness and muscle damage (Horita et al. 1999). This is understandable since the eccentric force produced is very high, albeit rapid. This may indicate that depth jumps are a powerful stimulus to stimulate structural adaptations.
However, depth jumps don’t lead to significant hypertrophy. So the nature of the structural adaptations following depth jumping isn’t quantitative in nature, but qualitative: an improvement of the strength and contractile capacity of each muscle fiber.
Soviet literature gives the following guidelines when practicing depth jumps:
1) The joint position upon landing should be as close as possible to that of an important sport action (Laputin and Oleshko 1982).
2) The amortization phase should be short enough to avoid losing the elastic energy produced, but long enough to allow for the shock stretching to occur (Laputin and Oleshko 1982). Research indicates that the elastic energy from landing is stored for up to two seconds. So in theory you have a window of two seconds between the landing and take-off phase. However, to maximize the training effect you shouldn’t spend more than one second on the floor.
3) The height of the drop should be regulated by the preparedness of the athlete. The heels shouldn’t touch the ground during the landing phase. If they do, then the height of the drop is too high (Laputin and Oleshko 1982). A height varying from 0.5m to 0.7m appears to be ideal for most strength and power athletes (Roman 1986).
4) Depth jumps have a very powerful training effect, so the volume of work should be low, i.e. no more than 4 sets of 10 repetitions (or 40 total jumps spread over more sets), two to three times per week for advanced athletes and 3 sets of 5-8 repetitions (or 15-24 total jumps spread over more sets), one to two times per week for lower classes of athletes (Laputin and Oleshko 1982).
5) Because of the very powerful training effect of depth jumping, it’s idiotic to perform this type of training systematically throughout the year. The shock method should be used in blocks of three to four weeks with at least four weeks between blocks (Roman 1986). In fact, some coaches recommend no more than two to three such blocks per year (Medvedyev 1996) and only when a rapid rise in power and reactive strength is needed to further performance gains.