CYCLING – TRI: why using power when you ride?

We all have a GPS or a HR monitor that we use during our ride. The down side is that the data recorded with these small computers aren’t enough representative of the intensity of the energetic output.

It is clear that the tiredness on a downhill is lower than the road but uphill!! The speed is influenced by the elevation, but also the wind or the presence of a pack. Comparing an average speed over a typical segment is therefore not very relevant. Yet it is a regular habit of cyclists and triathletes, to compare themselves on their fetish uphill (thank you Strava segments !!).

As for the heart rate, it is influenced by many factors but it is true as well as the power:

  • lack of sleep,
  • the dehydration,
  • the dynamic of the race (constant effort or not),
  • elevation.

The impact of fatigue or dehydration can often be observed when you wake up, with a feeling of heavy legs and, when you can measure it, a higher HR when you wake up than usual.

From the point of view of the race dynamic, we regularly observe that for the same average HR, the central exhaustion (nervous and cardiac) and peripheral exhaustion (muscular) is totally different between a TT and a classical road race for example: the frequent braking and acceleration are horrible. 

The power is a more stable data in time to be used in a clearly quantifiable and regular way. To put it simply, power is the force applied by our legs to propel the bike. At a given energy output is linked a power. The power data make it possible to judge the athlete's commitment to the bike during his effort.

Of course, a power is influenced by the same factors as a HR but to a lesser degree and especially without inertia: it is always the heart that allows the legs to turn. But the stability of the measurement over time allows a use on the bike in full effort and thus to evaluate the impact of each factor individually:

  • lack of sleep and dehydration will affect my power by X%.
  • The elevation above 3000ft, 5000ft, 6500ft or 8000ft will impact my power by X%.
  • the type of effort (how to quantify the effort on a sprint? will the HR have time to move higher?).

To take me as an example, furrowing the mountain passes around Mont Blanc:

  • I know that I am able to climb a long but low trail (yes it exists, starting from 0ft of elevation to finish at 3000ft for example) at 230-240watts for 2 hours.
  • On the other hand, I know that I am able to climb a long but high trail (from 4000ft altitude to finish at 6500ft for example) to only 200 watts over the same duration of effort. Elevation hampers my performance.

The power is more easily used during the effort, in the reflection on the pacing strategy (in TT or in triathlon) and a posteriori, in the analysis of the effort.

Thanks to the power measurement, we can follow the progress of an athlete during the season, observe the variation of the state of fitness in a precise way and, thus, optimize the trainings and the competitions. This is the Maximum Mean Power (MMP) created by Frédéric GRAPPE and Julien PINOT which we will talk about next week.

Nevertheless, it is important to have a look on the HR because I remind you, the heart is still one of the first link in the chain that allows us to crush the pedals: we can be able maintain a power called "confortable" but sometimes at a massive energetic output.

Laisser un commentaire