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The strength curve

Strength curve

Advanced knowledge, the seven factors in motion and how to improve them

Every body is different and there is no better place to observe this than personal training. With the Olympics preparations ongoing in Tokyo we encounter more and more athletes looking for advanced stuff. The strength curve is a comprehensive way to depict movement and to isolate specific aspects to be improved.

Concentrated curls or picking your nose, breathing or dashing, any movement at all, on a piece of paper looks something like the figure below:


Strength curve


  1. You rear back, getting in position, preparing to spring
  2. Transition from eccentric to concentric movement
  3. Force is applied, pushing, pulling, throwing, hitting
  4. Apart from powerlifting, acceleration time is kept short
  5. Maximum force is reached
  6. Absolute maximum almost never reached in any sport, maximum force is almost always a portion of that limit strength


The seven factors

Factor one: The angle of “Q” – This is the starting strength, the steeper the line, the greater the number of muscle fibers you will have recruited at that exact time. The starting strength is all about explosivity and the ability to recruit the maximum number of muscle fibers simultaneously. Best training to do so are compensatory accelerating training, plyometrics, olympic lifts and running drills.


Factor two: The angle of “A” – This is the sustained acceleration, usually short, it must suddenly drop at the maximum range of motion to start amortization. Once again when you train to improve speed and acceleration, compensatory accelerating training, plyometrics and olympic lifts are doing wonder. This is more of a neuromuscular training than a pure strength training.


Factor three: Force – The maximum amount of force output you produce during  any given movement is called Fmax. Fmax is improved by regular strength training such as weight lifting within the 4-10 repetitions range.


Factor four: Time – Tmax is the time taken to achieve a movement through its expected full range of motion. In most sports, but precision ones, we intend to shorten Tmax as much as possible. This is achieved by improving the factor one and two.


Factor five: The relationship between Time and Force – Some high school science class here:


Power is equal to the force times the distance per unit time.

More practically, Fmax divided by Tmax is the definition of explosive strength. Starting strength is the ability to turn as much as fiber on, explosive strength is the ability to keep them on. Those are absolutely different and should be considered as two different aspects to be trained. Collectively they are referred to as “speed strength”.

Consideration of speed strength is what really defines sports nowadays. In the past only limit strength was considered.

before and now in training

then and now


Factor six: The relationship between Limit Strength and Fmax – Tmax is so short that it is impossible to get all of your motor units turned on. Far from that! Hammering your limit strength is not the way for an athlete to become great. It would slow you down if carried to the extreme. Training limit strength was the paradigm followed by the Soviet Union athletes and we all know that those former records are now all beaten.

“Functional strength” comes into play and pretty much defines how much you should train your Fmax. This is defined by the amount of limit strength necessary to maximize Fmax without increasing the distance between Fmax and limit strength (resulting in speed loss). One’s strength-to-weight ratio is very different from sport to sport and this is also why there is no generic training to follow to be good at your craft. To each sport a specialized training.


Factor seven: The amortization phasis – Even if this phasis does not seem as critical at first glance, it is! Remember that the absolute majority of the injuries occurs during the amortization phasis. Think of powerlifing when performing the transition from downward to upward motion, or more ballistic motions such as pitching at baseball. Everything should be properly balanced, a limb to fast, too strong for its ligaments and tendons will sooner or later get injured. The best way to train amortization is to follow a proper periodized training, with well defined cycles. Those cycles will provide enough stress for your body to trigger adaptations and enough rest to repair micro traumas that would only worsen otherwise.


To sum it up

Y axis should be stretched as long as it stays functional and does not impact speed, X axis should always be shortened as long as your body is well trained enough to deal with such amount of power.

This is what separate modern athletes from antic ones, a sprint from a turbo waddle.

Strength curve's ideal evolution

Strength curve’s ideal evolution


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