Have you ever heard the saying – slow jumping is low jumping? These five words are referring of course to people who lack reactive strength. Reactive strength is very important for people wanting to increase their vertical jump.
In this four part series I am going to examine reactive strength and the various methods of training and developing it at length. By the end you should have a pretty good understanding of what it is, why it is important, and how is the best way to improve it.
Essentially reactive strength is the ability to absorb force in one direction and then apply more force in the opposite direction.
An older definition put forth in the 60’s was that
“reactive strength is a concentric contraction following a rapid eccentric contraction resulting in greater concentric force output” – Cavagna et al 1965
However, from a more practical point of view I prefer a more recent definition of reactive strength as
“the capacity to rapidly switch from an eccentric/yielding action to a concentric/overcoming action.” – Thibaudeau 2006
If you lack the capacity to quickly switch from the yielding phase of your jump to the overcoming, i.e. you lack reactive strength, you will have great difficulty effectively executing the jumping motion swiftly and powerfully, and as a result, you will not be jumping very high.
For many years sports coaches and trainers believed that reactive strength was primarily a result of long term plyometric training which they believed decreased the inhibitory effects of the golgi tendon organ allowing a the body to better use the stretch shorten cycle (SSC).
More recent research however has suggested that reactive strength is influenced very little by the SSC and more by the levels of eccentric strength the athlete has. This shift in thinking has led to a variety if different training methods being employed (which will be discussed in detail in the other parts of this series) besides the standard depth jumps and altitude landings that were (and still are) staples of many athletes vertical jump programs.
For the remaining parts of these reactive strength articles I use the terms reactive and eccentric strength interchangeably.
As you have probably worked out by now that an athlete wanting to jump high will need high levels of reactive strength. Without it the athlete will not be able to effectively absorb force as they run and jump.
This is important because when you plant your feet as you are about to jump you are applying a lot of force down into the ground. If you are not able to absorb that down force and brake your descent effectively your knees will buckle and you will be unable to then apply your concentric power back into the upwards movement of the jump.
Anyone who lacks eccentric strength will know the feeling of running in to jump and feeling their knees weaken a little bit right at the takeoff which causes them to lose momentum and power on the jump.
While high levels of reactive strength are definitely advantageous to jumping high, the benefits don’t end there. It also helps tremendously for participants in most team sports as it is one of the key factors in an athletes ability to change directions quickly.
Just like a jump is a rapid change of direction from down to up, a football player for example, trying to avoid a defender will also use a rapid change of direction to try and out manoeuvre their opponent.
As an observation, and I stress this is based purely on the athletes I have seen and not on any empirical evidence that I am aware of, the types of athletes that are generally (but not always) considered to be highly reactive, i.e. those guys that seem to really effortlessly get off the ground quickly, tend to be the lighter, or more slightly built jumpers.
This make sense if you believe (as I do) the idea that reactive strength is more about eccentric strength than the ability to exploit the SSC. The more mass an athlete has the more down force he/she will have to overcome.
If the athlete is fairly light on the other hand, then they will have to overcome far less down force and so will require relatively lower levels of eccentric strength to achieve the same result. It is also another reason most single leg jumpers are pretty skinny. Long jumpers and triple jumpers are classic example of this.
Now this isn't to say that you have to be light as a feather to jump high. You can still overcome a little extra muscle mass with higher levels of relative strength, and as a counter-point, in many team sports for example, a bit of extra muscle mass will provide a bunch of other performance benefits that will outweigh an extra couple of inches on your vertical you might potentially lose.
This introduction to reactive/eccentric strength has been pretty brief. As long as you know that reactive strength is essentially how eccentrically strong an athlete is, and that reactive strength it important because the more you have of it, the more quickly you will be able to absorb the downward force and reverse direction when you take off, then you basically know most of what you need to.
In the following parts I will discuss the stuff you probably are really interested in, the training methods used to develop it. I am sure you will enjoy these as there a number of them that are quite fun to do. Click the link for Part 2 of our reactive strength series which goes into what I call the 'classic' training methods.