Put Down That Power Meter, Eugene

A recent study, published in the Journal of Strength and Conditioning Research took a look at the two most popular training tools for cyclists, heart rate monitors and power meters, and the results challenge the current wisdom of coaches and athletes.

A quick recap: Heart Rate Monitors (HRMs for short) include a strap that goes across the chest to measure the beats of the heart and a receiver (a watch or head unit of some kind) that displays the current heart rate. With information on one’s resting and maximum heart rates, it’s possible to calculate target zones for different types of training zones.

Power meters record the power output of a rider, either through a hub or crank/bottom bracket combination that measures mechanical strain and translates that into wattage numbers. By riding at different wattages, it’s possible to perform various types of training and it’s possible to see what a rider’s maximum output is.

Heart rate training is more subjective than power meter training–many things can change a heart rate from dehydration to overtraining while the power output by a cyclist is an empirical measurement of how hard they are working. (If you can kick out 400 watts, it doesn’t matter if your heart rate is 150 or 180, you’re still producing the same amount of power.)

Over the last few years heart rate training has declined while power meter training has increased–with most cyclists feeling that they’re getting better results with power meters. The average or beginner cyclist has been left out of the revolution though because of the high cost of power meters relative to HRMs. (A cheap power meter still costs over $1000 while a good HRM can be had for less than $100.)

The study from the Journal took a look at both training methods to determine their effectiveness and see if power meters really hold an edge in high-intensity training. Counter to common wisdom, they do not.

Looking at twenty-one “well trained” cyclists between the ages of 26 and 38 the study divided the riders into HRM based groups, power meter groups and a control group. For four weeks the cyclists were trained at fixed power output or fixed heart rate levels corresponding to 80% of their peak power output.

After four-weeks of high-intensity training the two groups were evaluated again in peak power output, and 40-km time trail performance. Both groups showed significant improvements in output, but the HRM trained group showed significantly greater increases in peak output (5.0% vs 3.5%).

The researches concluded that “the [heart rate] group showed greater probability of a beneficial effect for peak power output. The current general perception that prescribing training based only on power is more effective than prescribing training based on heart rate was not supported by the data from this study. Coaches who are unable to monitor progress frequently should prescribe training based on heart rate, when intervals are performed under stable conditions, because this may provide an additional advantage over prescribing training using power.”

Now, there are some obvious limitations to this study; the cyclists were only trained for four weeks (much shorter than the average season), they were already well-conditioned and the published results don’t indicate what they did between sessions. For professional racers who might be out every day in a constant state of dehydration and sleep deprivation, the power meter training might find a better home as part of their regime.

But for the average cyclist faced with the costs of a power meter vs. the costs of a heart rate monitor, the results of this study are pretty interesting. Until the next training fad comes along, it’s possible to use a heart rate monitor for hard-core training without feeling like you’re stuck in the 1800’s. And think how easy it will be to teletype your results to your training partners in the Old Country.