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In descriptive words Power is in essence a measure of how effectively or quickly we can apply a force. It is in some ways an evolution and progression of strength, which itself is simply the ability to exert a force (move a load/overcome a resistance) no matter how quick. In more matter-of-fact, scientific terms Power is the amount of work done per unit of time (with work measured in Joules and Power in Watts).

P = W / t

Because work is the mathematical product of force and distance and in the case of athletics the distances are largely controlled by the anthropometry of the athlete, we can ignore distance and state more simply that power is force per unit time.

If W = f x d and d is constant (then d can be ignored conceptually)

Then P = f / t (1)

This can also be rearranged in a way that states power is equal to the product of force and velocity.

If P = f x d / t and v = d / t

Then P = f x v (2)

This implies that if we know from measurements an athlete’s force values and either their contact time values or velocity values then we can calculate power values indirectly. This can play out in two contrasting ways. If the athlete is running, the measured data will be force (ground reaction force) and contact time (ground contact time), where as if the athlete is performing Olympic lifts in the gym it is most realistic that we will be able to measure force (load) and movement velocity. Hence depending on the environment and type of training we can make use of either power equation (1 and 2 above) for our needs.

for running the measured data will be force and ground contact time

So why would athletes need to care about Power as a measurement? As stated earlier power is in essence a way to qualify how effectively or quickly the athlete is applying a force. For a runner this force is applied into the ground during a single foot ground contact during which time the foot is stationary. In more abstract terms it’s telling the runner how hard they are working, combining the effects of both mechanics and physiology.

For many running enthusiasts. coaches and practitioners the pre-existing method for quantifying how hard a runner was working, heart rate, was not enough. Whilst heart rate could highlight the workload on the cardiovascular system it didn’t address other important factors in performance such as muscle strength, neuromuscular activation, synchronisation and timing, form and biomechanics, and leg stiffness and elasticity. Added to this were the well known drawbacks of heart rate response lag time, effect on heart rate of extrinsic factors and so on. So it was hoped that the development of Power measurement in running would give end users a ‘true’ mechanical measure of how hard the athlete was working that could respond immediately to dynamic intrinsic and extrinsic changes.

Now that the scene is set in terms of what Power is, how it’s calculated and what it’s providing to the athlete, the next power article will dive into how the runner can begin to apply power to their training at a conceptual level.

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M.Sc, MSci, B.Sc, CSCS, NSCA-CPT, XPS, CGS. Malc Kent is a professional coach, internationally respected applied scientist and former world class athlete. His services include sports coaching and mentoring, workplace coaching and biomechanics coaching.

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