In this third part former TV Gladiator and record breaking GB pole vaulter Kate Staples concludes her look at the definitions of speed, power, strength and training for them.

Explosive strength deficit (eSd)

It is possible for a person to develop their maximum potential force in around 0.3-0.4 seconds , however there are some some sporting motions that have far less time available to exert this force – i.e throwing a javelin. In this kind of instance there is clearly a deficit.


The difference between the maximum force we could develop and the force we are able to develop in the time allowed during the explosive movement, such as throwing a javelin or putting a shot, is what is known as the explosive strength deficit.

As the resistance/weight of the object decreases and time available to apply/develop force becomes shorter, the difference between the force we are able to generate in the movement and the maximum force we could develop with unlimited time, the ESD becomes greater.

Clearly, the ESD is a measure of what percentage of their total strength potential an athlete is using when performing explosively. Often the percentage will be quite low and ESD large for all of the reasons previously discussed.

This begs the question, if an athlete can never even get anywhere near to the maximum force they could develop under optimal conditions then

…why do so many athletes spend so much training time lifting heavy weights slowly?

This is a training method far more akin to that of a powerlifter whose sole objective is to lift a maximum weight and whose explosive strength deficit is practically zero.

performance fitness_6We have also already seen the impact of this style of training on the previously studied force-velocity curve.

The importance of ESD can be seen in the sport of weightlifting. It is important to note that a number of the greatest powerlifters of all time have tried their hand at weightlifting.

Regardless of being some of the strongest men who have ever lived and enormously impressive in powerlifting terms, they were not actually the most powerful in the sense that we are defining here and they certainly did not make the best weightlifters.

The ESD in the sport rendered their huge maximum strength largely moot.

The impact of momentum

Momentum can be calculated as Mass x Velocity.

As an example: If we have a cricket ball moving at 40m/s with a mass of 0.15kg, it has momentum of 40 x 0.15 = 6(kg*m)/s.

In essence, it is the momentum we generate in a javelin, a shot put, a baseball bat, a gloved fist, a cricket ball or our own bodies which is the determinant of performance.

Here’s an interesting thought regarding momentum:

Imagine there are two athletes, one performs a jump squat with quite a light-weight, perhaps a fraction of their maximum squat such as 40kg, whilst the other squats their maximum figure of 220kg.

– We know that in the first example, thanks to the speed generated and lack of opposing force, the person would leave the floor. They would have developed serious momentum because, although the additional mass was relatively incidental, yet the speed they generated was very high.

– In the second case, the person is forced to move slowly because this is governed by the considerably larger mass and the volocity and momentum involved are almost zero.

Take a second to consider sprinting or jumping

As we looked at back in Part 1, the contact time with the floor in sprinting and jumping is fractional – around 0.1s. That is the time available for an athlete to lay down as much force as possible. Not long is it?

This is why there is talk of the importance of ‘rate of force development.’

The more force the athlete is able to develop and apply rate of force development, the greater their velocity will be when they leave the floor and the fater they will travel.

performance fitness_7The greater  the velocity the more significant the momentum and thus the further or faster an athlete will travel in the jump or between strides.

So lets now get down to some definitions:


This might appear simple but there are many different definitions of strength and there are in fact many different types.  But for the purposes of this article, and allowing for the fact we don’t want to run into thousands of words, we can define strength as:

The ability to generate absolute maximum external force. 

In practice our level of pure strength is the weight we are able to lift once only. You may have heard the the phrase ‘1 Rep Max’.  That is the single optimum power exertion action.

Powerlifters have the highest level of pure strength of any athlete. Hence we can talk about our strength as an ability to develop maximum force.

Yet, taking into account everything discussed above, a broader understanding of strength can only truly be defined in relation to the speed at which it is applied.

Someone can be ‘strong’ at a low speed, e.g. a powerlifter, but ‘weak’ (and I use that term relatively) at a high speed. Taking the shot putter or javelin thrower as expamples again, these athletes are strong at high speed.

Developing strength

There is no great revelation or secret here – the most effective way to develop pure strength is to lift very heavy weights for few repetitions, perhaps 1-5 only, using exercises such as deadlifts, squats and bench presses.

However useful this might be in terms of developing strength, it always needs to be borne in mind whether it is strictly necessary and applicable to an athlete’s requirements.

There is an exception though – the development of maximum strength may also be seen as more of a priority in an athlete’s formative years.

There is quite a bit of evidence that shows that in athletes with less strength training experience, simply ramping up pure strength will have a huge, positive impact upon power and performance in a multitude of sports and activities.

But what happens in the end is that the athlete becomes, in a sense, ‘strong enough’ and the concept of the ESD comes to the fore.


Speed or velocity is how quickly an object would gets from A to B at the rate it is moving at any given instant. We’ve looked at the importance of speed to momentum and thus as well as the negative potential impact of pure strength upon speed (remember the shift of the force-velocity curve with powerlifting style training).

People often ask, “Will weight training make me slow?

It is a good question and, at risk of sounding too obvious, the answer is” “Slow weight training will make you slow. Fast or explosive resistance training will make you fast and explosive.”


Power is the product of force applied and the speed at which is applied. It can be calculated using the equation: Power = Force x Velocity

High levels of power allow an athlete to develop a huge amount of force very quickly. We can say that their rate of force development is high. As noted, more force brought on in a quicker time means greater velocity and thus greater momentum. Look at championship level arm wrestling. Technique-wise it is clearly about huge amounts of speed. These people do not crank up the power slowly and deliberately, they explode into the fastest movement they can immediately. Does the stronger aathlete always win? Probably not, does the fastest armwrestler with great technique win? Almost certainly.

Technically we must distinguish ‘power’ from ‘rate of force development.’ Power is really a flow – we understand this when we think about the wattage of a light bulb.

Power is a measure of our ability to continually develop high force at high velocity for a period of time.

However, our rate of force development is a measure of our efficiency in developing force quickly. If you know your cars and could use a metaphor at this point – power is BHP and rate of force development is akin to torque.

As long as an object is being moved, clearly it involves the development of power.

performance fitness_8And in the same way some velocity will always result in some power. So in a slow squat, power is generated, but not to the degree measured in the forceful and very fast Olympic weightlifting manoeuvres.

If we come back to the shot putt this emphasises the huge impact of speed/velocity on power and therefore performance.

All power is not the same power. To put them all in the same box, and therefore train in a one-size-fits-all kind of way would make no sense  at all.

The Russians make an interesting division here. They speak in terms of ‘strengthspeed’ (power developed by a weightlifter attempting a maximum clean and jerk) and ‘speed-strength’ (a shot putt, javelin throw or punch).

‘Strength-speed’ or ‘speed-strength’ can therefore be developed using absolutely appropriate training methods.

Hopefully these explanations and examples help explain that the development of sport specific strength and power is about more just lifting heavy weights like a powerlifter or a bodybuilder. Getting this wrong can make training somewhat futile futile and potentially damaging to the athlete in terms of performance improvement. But as and where appropriate you should also you should also grasp the potential benefits of explosive lifting and ballistic training. It can make all the difference!

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