The Explosive Strength Deficit (ESD) is something we should be very aware of when training in self protection, especially when training strikes. With that said, let me give a brief explanation of what the ESD is and how we can train to minimise its effects.
The ESD is the difference between how much force we can develop if we have an unlimited amount of time against how much force we can develop when our time is limited.
Let us look at an example to make things a little clearer. Athlete ‘A’ who is a shot putter, can bench press 240kg, taking 0.5 of a second to generate enough tension in his muscles to lift the weight. This lift equates to athlete ‘A’ producing 120kg of force per arm when there is no time constraint.
Now if we examine the time it takes athlete ‘A’ to throw the shot, we discover it takes 0.18 of a second, less than half the time required to complete the 240kg bench press. Due to the short duration of the throw, athlete ‘A’ is never able to generate the full 120kg of force per arm we know he is capable of producing and this is the ESD in action. Research carried out by sports scientists show that a well trained athlete is generally able to apply between 50% and 60% of the total force output and this is all due to the constraints of time.
To improve our force output and minimise the ESD we must improve our ‘Rate of Force Development’ (RFD). By making improvements to our RFD, we increase the amount of force we can apply a short time and there are a number of ways in which this can be achieved.
Firstly we can train to improve the velocity of the movement by moving a small external mass. For example, if we are working on a palm heel strike, we could throw a 2 or 3kg medicine ball. The reason for the light weight is to minimise any change to motion used in the palm heel strike. This is down to the concept of specificity, where if the motion changes too dramatically you get good at doing something which is no longer a palm heel strike. By throwing the light medicine ball we are able to concentrate on increasing the velocity of the strike, which in turn leads to more power. Here we would propel the medicine ball on a linear plane for as far as possible.
Another protocol for training the RFD would be working with very heavy weights and this would concentrate on development of the fast-twitch muscle fibres involved in the palm heel strike. Working with heavy weights does present the problem of specificity, so again we have to ensure that the exercise and the weight used in the exercise does not impact negatively on the motion of the palm heel strike. Cable machines are excellent for this type of exercise, as they allow you to work on the body mechanics of the strike without having to worry about supporting the weight against the pull of gravity. You can concentrate fully on perfecting the explosive action required. As an alternative, remove the static weights of the cable machine and attach lengths of chain. As more chain leaves the ground, the load gets heavier; this in turn forces you to accelerate throughout the whole movement.
Finally we could use ‘complexes’ to train our RDF. Here you would perform a set of 20 press ups and then go straight into a dumbbell throw, with a 20 or 30 pound dumbbell. By performing the press ups before the explosive throw we are able to exploit the tension created by the non explosive movement and use it to increase the power output of the explosive one. When doing this keep the explosive reps to around 5 per arm for each twenty push ups.
For a more in-depth discourse on this subject please see ‘Science and Practice of Strength Training, Second Edition’ by Vladimir M. Zatsiorsky, William J. Kraemer.