Jumping is a critical skill in many sports. But when we talk about jumping performance, we need to be clear about the jumping skills we are wanting to improve. Different sports require different types of jumping. By understanding the vertical jump in more detail, we can gain more insight into training the physical needs required to jump higher.
When you analyze jumping in different sports, three categories of jumping appears:
|Jump type||Sports examples|
|Double leg from standing position||Jump to block in volleyball
Jump ball in basketball
Jump in various field team sports
|Double leg from run-up||Jump to spike in volleyball
Dive from 10m platform
|Single leg from run-up||High jump (track and field)
Jump in various field team sports
Each category requires somewhat specific skills due to differing technical and physical demands. A single leg jump requires coordination in swinging the free leg, which does not apply to a double leg jump. Likewise, a jump from a run-up requires the ability to convert horizontal run-up speed to vertical velocity.
All this means that an athlete who is relatively good at a double leg jump from a standing position, may not be so good at a single leg jump from a run-up, and vice-versa. There are two practical take aways from this:
- Coaches must know the jumping demands of their sport before prescribing training to improve jump performance. They must determine what the dominant jump types are.
- If there is more than one jump type needed in the sport eg. basketball, the coach should assess their athletes to know what their jumping strengths and weaknesses are. This can easily be done with the use of a jump testing device like a Vertec or yardstick.
The effect of the run-up
The figure below shows the relationship between the number of steps in the approach run and jump height for both double and single leg take-offs.1 Participants were asked to run up faster as they increased the number of steps in their approach. The graph shows that the best jump height (on average) was achieved with the 5 step approach for the single leg take-off, and with the 3 or 5 step run-up for the double leg take-off.
There are two important trends from this graph. The first is that jump performance improves as you run-up faster, to an optimum point. The reason for this is that as you run-up faster, you can swing the free limbs faster and produce more force with the take-off leg, resulting in greater vertical ground reaction forces, and vertical velocity generation.
The second trend is that jump height declines at relatively faster run-up speeds when you go beyond the optimum. Remember that the graph shows an average curve for one particular group, but curves will vary among different athletes.
There are likely two reasons for the declining jump performance with the fastest run-up:
- An inability to coordinate the skill. In other words, the athlete is “out of control” when moving at a speed that he or she is not accustomed to. It is quite possible that practicing run-ups a bit faster than the current optimum, may reduce the decline in jump height at the same run-up speed.
- An inability to tolerate the load on the take-off leg. This is especially likely when performing a single leg take-off because one leg has to absorb a large impact force and eccentric or muscle stretch load. The faster the run-up, the greater the load. If the leg isn’t strong or ‘stiff” enough, it may “buckle”, or at least result in excessive hip and knee flexion, and loss of take-off power.
Reactive strength and plyometrics
The ability to absorb a relatively high eccentric or stretch load and quickly produce a forceful extension of the leg is known as reactive strength. Reactive strength is a unique and specific physical quality.2 Athletes that are strong and powerful, do not necessarily possess good reactive strength. For example the best squatter is not always the most reactive. The reason is that these qualities are determined by different neuro-muscular mechanisms. Leg strength and power are largely determined by the amount and structure of muscle tissue, and the ability of the nervous system to activate the relevant muscles to achieve a high rate of force development. These qualities can be developed through traditional weight room exercises such as Olympic lifts and their derivatives. However reactive strength is also influenced by the elastic properties of the muscles and tendons, the activation of stretch reflexes, and the pre-activation of the muscles. Pre-activation refers to the muscles being active before the take-off leg makes contact with the ground. This increases the stiffness of the leg, and therefore the leg is prepared for the high impact forces and eccentric loading that follows.
The main way to train reactive strength is through plyometric exercises such as drop jumps, bounding, or any exercise that involves a landing and a subsequent jump, over a relatively short ground contact time (e.g.<250ms). Exercises such as countermovement jumps, vertical jumps, jump squats with a barbell from a standing position are too long (>250ms), and although they may be effective for developing the rate of force production, they are not very useful for the development of reactive strength.
A training study that I conducted as part of my doctorate showed that athletes who performed six weeks of plyometrics (drop jumping with a short ground contact time of <200 ms), achieved a 15% gain in reactive strength, without any improvement in maximum strength or pure concentric leg power.3 In terms of transfer to jumping performance, the gain in the double leg jump from a standing position was only 2%, whereas the jump from a run-up and single leg take-off was enhanced by 7%. This shows that plyometric training that targets reactive strength is especially effective for improving jumps performed from a run-up.
A theory about double leg take offs
Although not confirmed by any research, I have observed that some athletes that prefer to jump from a double leg take-off, tend to have poor reactive strength. This makes sense because when two legs are used, the landing and eccentric load can be spread over both legs and over a longer time (if the feet land in quick succession). The graph above shows that single leg take-offs tend to produce greater jump heights that double leg take-offs. This may be because in a single leg take-off, the free leg contributes to the vertical force produced, and the support leg can be used as a lever to convert horizontal run-up speed to vertical velocity. Therefore, if athletes who lack reactive strength can develop this quality through plyometric training, they may be able to perform more single leg jumps effectively, and improve overall jumping performance.
- Young, W., MacDonald, C., Heggen, T. and J. Fitzpatrick (1997). An evaluation of the specificity, validity and reliability of jumping tests. The Journal of Sports Medicine and Physical Fitness. 37: 240-245.
- Young, W., Pryor, J.F. and G.J. Wilson (1995). Effect of instructions on characteristics of countermovement jump and drop jump performance. Journal of Strength and Conditioning Research. 9,4: 232-236.
- Young, W.B., Wilson, G.J. and C. Byrne (1999). A comparison of drop jump training methods: effects on leg extensor strength qualities and jumping performance. International Journal of Sports Medicine. 20, 295-303.