CYCLING – TRIATHLON: what about Critical Power?

Critical power is another way of thinking about power training, even though many concepts with the PPR ate very close.

There’s a mathematical relation to define the peak power peaks from 2 measurements (CP5 and CP20 for example): we can extrapolate the CP on intermediate durations (between 5 and 20 minutes), before 5 minutes and beyond 20 minutes.

This is the basis of the Coggan thinking model: a time-relation to a power!

Unfortunately, the mathematical relationship comes up against the specificity of each human body:

1. What are our capacities to mobilize an important strength and to use our phosphocreatine reserves during sprints?

2. What is the kinetics of our lactatemia? Recycling lactate production?

3. What is our ratio of lipid/carbohydrate use over long-term efforts?

4. What is the motor efficiency of the pedaling of each of the trained athletes?

A mathematical relationship is an intangible rule: the genetic and the training make each cyclist unique. It’s very comfortable to extrapolate performances but there’s a too wide variation in performance to have credible coaching.

The coach uses measurement and not extrapolations (when it works, it's fine if not ...), so we have a real performance monitoring.

To answer question # 1: strength is not just about the size of a leg; strength comes from our ability to massively and rapidly contract a large number of muscle fibers. It also comes from the help of complementary muscles in order to create an action synergy.

We can imagine that, in the pedaling pattern, the quadriceps and the glutes work together after passing the neutral point.

You will also have to ask the antagonistic muscles to be "relaxed" to not to hinder the gesture.

According to our sporting history, our genetic basis of strength, all this is very variable.

Concerning the reserves of phosphocreatine: traditionally, we explained to sport’s students that the alactic function works no more than 10’’ because it’s the duration of a 100m sprint in athletics.

This observation can be valid in particular “with no warm-up” efforts with an oxygen supply far below the demand.

However, when there is an oxygen consumption steady-state (O2 intake = O2 consumption), the use of CP is in a steady-state too and CP is re-synthesized as quickly as it is consumed.

Indeed, when there is a significant ATP production thanks to aerobic metabolism, a part of the ATP is instantly associated with creatine to reform phosphocreatine (and therefore an ADP).

Do you follow me? In fact, depending on our level of endurance and sprint training, our ability to restructure CP varies! Big endurance skills also give big sprinting skills![1]

To answer question # 2: long and intense efforts impact muscle use of glucose, we talk about anaerobic glycolysis.

This glucose is transformed into pyruvate and potentially into ATP (the only fuel that can be used directly by the muscle) in the mitochondria, which function is very slow.

In parallel, during the short climb or during the first seconds of an “attack”, this pyruvate is produced very quickly and will be accumulated at the periphery of the mitochondria which cannot use everything so quickly. 

This pyruvate will, therefore, be transformed into lactate, 100 times faster than mitochondria would have used.

Again, there are marked individual differences that a mathematical model does not take into account.

The advantage of lactate is that it is not such a bad thing because it is an ATP production booster! Again, depending on our physical condition and our propensity to make violent but prolonged efforts, the impact of lactate will be variable.

We are entering a more complex area not only based on the habits of cycling training; I use the basis of biology which allows us to understand why and how our organism progresses. See you next week.

Frederic HURLIN -

[1] Dynamic asymmetry of phosphocreatine concentration and O2 uptake between the on- and off-transients of moderate- and high-intensity exercise in humans, Rossiter and coll. J Physiol,2002.

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