When talking about the one leg jump the “general consensus” is that this way of jumping is to be named a “reactive jump” because it relies heavily on the reactive ability of that particular athlete.

While this is a general name for the one leg jump, “reactive”, the reality is that the one-leg jump has two ways of occurring. The first way to jump off one leg is using your strength to provide the force/upward momentum. The second way of jumping off one leg is using the deformation of the jumping leg tendons to provide the force/upward momentum.

These two technique, because we’re talking about technique in here, are pretty different from one another. Yes, of course both the reactive and strength qualities combine for either of the technique, but at different levels of involvement.

Let me explain:

1) The strength jump

In my experience, most people that haven’t trained in track and field and have developed a good one-leg running jump with basketball or other sports just by playing, and not by dissecting the technique behind the jump – are into this category. How can this be characterized? Well, a strength jump off one leg has these characteristics:

a) The run up is usually short – this means at most 5 steps;
b) The hips drop a lot, the center of gravity is lower than for the reactive jump;
c) Longer last stride;
d) Less linear (more rotation occurs at the hip);
e) Longer GCT in the amortization phase (for more strength to be applied);
f) Non-jumping leg pendulation (if the athlete jumps off the left leg, the right, non-jumping leg will “pendulate” (or the non-jumping foot will scrape the running surface);
g) The last step (takeoff) is at approximately the same length, and has approximately the same hip height as the penultimate step;
h) The jump occurs during acceleration.

Let’s work on the reasons behind all this:

a) The run up is short because you need a slow, controllable speed to apply force properly. At least, at lower levels of athleticism. You can have a longer run-up and still be a strength jumper if you have the necessary strength. If you’re strong and use a longer run-up but still do the next “strength jumping” points then you’re probably still a strength jumper.

b) The hips drop a lot because, in order to produce a lot of force, the more ROM you have the more force you can produce and this also elongates the GCT (ground contact time) which, in turn, gives you more time to apply force voluntarily.

c) The longer last stride occurs, again, because of the need to produce force over a longer ROM (range of motion). This also elongates the GCT and allows for more force to be produced (since there’s more time available to produce it).

d) Less linearity – this is a personal observation and it might or might not be a reality. In my experience, people that are strength jumpers also rotate more at the hip when they take off than reactive jumpers. We’re talking about jumping towards the rim in basketball and not in the high jump.

e) Longer GCT – As I said above, a longer GCT is needed for more strength to be applied.

f) The pendulation of the non-jumping leg occurs because the last step is longer and the hips are lower. This means the blocking effect occurs as well (the jumping leg acts as a “pole”) – but at a different angle that what happens for a reactive jumper. The non-jumping leg usually has less ROM to “attack” or “strike” vertically into the jump itself because of this.

g) The difference between the last step and the penultimate step is little in terms of stride length. This is because of the reasons above.

h) The jump occurs during an acceleration phase because the muscles can work to produce voluntary force during an acceleration phase. During a stable/top speed phase, the muscles will work as stabilizers and contract isometrically. For example, in a top speed sprint the calves don’t contract concentrically to extend the ankle. The ankle is extended ONLY by the effect of the recoil that occurs in the Achilles tendon.

Now, if improvement wants to be made for this category (say you have a strength jumper that wants to increase his strength and maintain his jumping style, and therefore jump higher because of the strength increase “only”) – then you need to emphasize a training plan meant to increase the qualities, technique-wise, as mentioned above.

Examples of this include acceleration jumps (where the athlete constantly accelerates towards the take off point), long ROM jumps (like deep lunge jumps, deep split squat jumps), strength work (long lunges for strength) and probably deeper depth jumps to provide more “load”. I’m not going to get into the depth jump contact time argument now so please bear with me.

Also, you’ll probably want to work on increasing posterior chain strength the vast majority of time, with the quadriceps and calf part being important, but not “that” important.

2) The reactive jump

In my experience, most people that have been training in track and field have this kind of jumping technique. In the track and field people are told to have a short last step (takeoff phase) and a pretty long/lowering the hips for a just a bit penultimate (for example, the “accepted” norm in the long jump is just 10% hip lowering, anything beyond being considered “more than optimal” (although the average is ~14%)). How can this be characterized? Well, a reactive jump off one leg has these characteristics:

a) The run up is usually long – this means more than 5 steps;
b) The hips drop a just a little, the center of gravity is higher than for the strength jump;
c) Shorter last stride;
d) More linear (less rotation occurs at the hip);
e) Shorter GCT in the amortization phase;
f) Non-jumping leg has a heel to the butt into extension forward dynamic;
g) The last step (takeoff) is shorter and has a taller hip height than the penultimate step;
h) The jump occurs in at a constant speed.

Let’s work on the reasons behind all this:

a) The run up is usually long to prevent/will prevent the jump from becoming a strength oriented jump. If you take a long run up then the muscles will contract isometrically in the plant just to stabilize the tendons. The tendons will deform and this deformation will then release kinetic energy that will be used to propel the body upwards. It is longer also because you’ll be able to get a faster plant speed with a longer run-up in order to use more kinetic energy that will, in turn, make your bodyweight less important (since you’re going to have initial speed that will negate the bodyweight).

b) The hips drop less than in the strength jump – in fact, the hips will lower in the penultimate step phase and will start to rise a bit from that point on. This shortens the GCT and allows for more tendon recoil to occur.

c) A shorter last stride is used because that’s going to put the body in it’s optimum position to jump vertically, using the jumping leg as a “pole” or lever. A shorter last step also allows for a quicker jump off the floor, or a shorter GCT (yes, I know, these things are somewhat redundant in nature).

d) I have personally observed a more linear approach for the longer run-up kind of athletes towards the take off point. Like I said, this is just my impression. If you compare guys like James White (reactive jumper) and LeBron James (strength jumper) you’ll see that James White has a much more linear approach towards his jumping point, whereas LeBron has a much curved approach towards his jumping point. Again, just an observation that’s not limited to just these two players/athletes.

e) Redundancy – a shorter GCT. We’ve talked about this already.

f) The non jumping leg has that movement (heel to butt to extension) because of the track and field background as well (this technique is used at both long and high jumping, and in athletics in general). It occurs because the hips are not as lowered as in the strength jumping example, and the last stride is shorter as well, which means the body is more vertical and more compact than for a strength jump. This means that in order to transform the horizontal momentum to a vertical momentum, and “load” the pole properly (the left leg, or jumping leg) in a compact, “non-leaking” way, the right leg has to move in a certain way as well. Whenever a limb is too far from the body that limb is hard to stabilize/control (unless great strength is available) and that’s when the “compactness” is lost, if you get the idea.

g) The last step is shorter in order for all the above things to occur. Again, redundancy.

f) The jump occurs at a constant speed. This is because the jump is tendon-deformation oriented, or reactive, whereas in the strength jump, the basic tenet was strength and range of motion. At a constant speed the muscles act isometrically allowing the tendons to provide the kinetic energy.

Now, if improvement wants to be made for this category, then you need to emphasize a training plan meant to increase the qualities, technique-wise, as mentioned above. You can make a strength guy go with this technique and also increase his performance because he has the strength. A reactive guy trying to emulate a strength jump will probably have a hard time.

Examples of this include constant speed jumps (where the athlete establishes a constant speed towards the take off point), short ROM jumps (like short step, high center of gravity lunge jumps, high knee angle split squat jumps), strength work (short ROM lunges for strength) and depth jumps with minimum knee bend.

Also, you’ll probably want to work on increasing posterior chain strength but also work on the stabilizers more, meaning the quad work with partial ROM squats (think – 1/4 and 1/2 squats) is advisable in this situation. Calf work is more important here as well because the calf will aid in stabilizing the lower leg and also increase the positive proprioceptive feedback that will allow for more speed to be used in the plant which will allow for more tendon deformation to occur.

To put things into perspective, here’s an example of a training exercise according to what you want to obtain for it:

5 step acceleration maximal 1-leg vertical jump (strength jump)
vs
10 step constant speed maximal 1-leg vertical jump (with a 5 step acceleration lead-in) (reactive jump)