Heart Rate vs Power

For the best part of a year I've been boring anyone keen or otherwise on the sport with my love for training with power (ie wattage).

Last October I rented a simple powertap unit from the good people and CyclePowerMeters and after a few months convinced Mrs T that I really, really needed to spend the best part of £700 on getting my very own.

Above: My PowerTap SL+

Heart Rate vs Power

So what's wrong with using the traditional HR model for training?

Well nothing really.

I used HR as the key measure of physiological response to training and exercise for many many years although its use has limitations namely that its confounded by variables that act upon it which in turn lead to inconsistencies.

Bodily hydration levels, air temperature, tiredness, caffeine, how well you slept last night and many other variables which can all combine to reduce its effectiveness as a training tool. On the other hand, power as a measure of physical exertion isn’t confounded by such variables.  300 watts is 300 watts.  Period.

This is most apparent for interval sessions where HR lags behind effort which means it's a poor measure of work done in the session. Hopefully the graph below demonstrates this. 

In this 2 x 20min interval session my HR as shown by the red line clearly rises over the course of the two 20 min intervals whereas the wattage I produced, the yellow line, remained essentially consistent throughout.

Above: 2 x 20min interval session - HR in red, power in yellow & speed in blue

For measuring performance and providing feedback on effort there's really nothing better for pro or amateur hobbyist bike riders alike.

So how do I use my PowerTap?

In essence, I use it for 3 things:

• To guide and pace effort for intervals and rides out on the road and on the rollers
• To track changes in fitness vs physiological strengths and weaknesses
• For motivation to train harder and to make indoor work a little less dull

So really that's it.

There are of course other uses of a power based training system which perhaps I'll look at over the course of this little blog.   Should anyone want to know more I'd point you in the direction of Training and Racing with a Power Meter which explains all in a far better way than I ever could.