Why Train With a Power Meter?

Why train with a power meter? I am a recreational mountain biker who really enjoys going out to the mountains on my bike. Mountain biking is a though sport and being as fit as possible comes in handy to make those days in the outdoors more pleasant.

I know that to enjoy mountain biking and keep within the group rides, I have to train.

In reality the only way to get fit is to go out and ride your bike as much as possible. But using some help from technology is welcome.

Heart rate-based training has helped a lot, but being in the MTB scene, meant power-based training information was coming from many sources, claiming the great benefits it provides.

For almost two years at the time of writing this post, I have been using a power meter for training, which has proven to be a very valuable tool, especially in the last few months when I understood and got the right tools to get the most benefit out of it.

It has been a long but worthwhile learning curve which I do not regret.

Let’s see why a power meter is a great tool for training.

Note: This post is part 1 of 5 of a series on how to start training with a power meter. If you came here as a result of a web search, make sure to go the starting post to take full advantage of the series. If you have not done so yet, please read the section About Training with Power, where we explain our approach to sharing the Training information in this website.

 

A BC BIKE RACE EXPERIENCE

Back in 2011 I had the privilege to ride (no race) the BC Bike Race (https://bcbikerace.com/ ). It had been in my to do list for a while and, after I got my spot, I was really happy I would finally go.

I had never been to a stage race. I was aware it would be very difficult, so some structured training was on order. After searching and getting recommendations, I purchased a Stage Race Training Program by Chris Eatough, six-time 24-hour solo World Cup champion. It was a 12 week training plan that showed session intensities as a percentage of effort.

At that time, I was using a Polar CS200 bike heart rate computer and I translated those efforts to heart rate zones. I followed the plan as close as possible and it got me to a good enough fitness to participate and finish the race.

Though I am very proud of my accomplishments in the BC Bike Race, for several months I had in the back of my head I could have been faster and get a better place on the race. In the next few years, reading about power meters made me think I could have gotten better results in the BC Bike Race shall I had a power meter.

It seems the power meter niche has traditionally been in road cycling and triathlons as for years there were very few (and expensive) options for mountain bikes.

BUT WHY IS A POWER METER A BETTER TRAINING TOOL? THE QUEST TO MEASURE EXERCISE INTENSITY

In order to improve fitness, there are 3 components to be controlled and monitored:

  • Frequency or how often you train, like how many days a week. Easy to measure and control.
  • Duration or for how long you train in each session. Easy to monitor and control as well.
  • Intensity or the amount of effort you sustain in a session. This has been the hardest component to accurately measure until the advent of the power meter.

The most common methods used to measure intensity before power meters are Rate of Perceived Exertion (RPE) and Heart Rate.

RATE OF PERCEIVED EXERTION METHOD (RPE) TO MEASURE INTENSITY.

This is a scale from 1 (very easy effort) to 10 (very hard effort) in which, according to how you felt during a training session, a rate is assigned. Perception may be affected by many external factors of daily life that cannot assure it is really measuring the training session by itself.

There is another scale from 1 to 18 that has the same purpose but I have never seen it being used in practice.

HEART RATE BASED INTENSITY MEASUREMENT

This method consists in finding either your maximum or your threshold heart rate and then derive intensity training zones based on heart rate ranges. So, depending on your training plan, you would strap on your heart rate monitor and make sure that during the session, you got to the prescribed intensities by sticking to the heart rate zone for the assigned duration.

Modern heart rate monitors and applications now allow to calculate a metric called TRIMP to assign the session an Intensity score. TRIMP is a very powerful method to monitor exercise intensity and load, especially in sports where means to measure power are not feasible or available.

Though highly more accurate than RPE, heart rate may also be influenced by external factors other than exercise such as ambient temperature, life stress, sleep quality and so forth that cannot assure it is really measuring the training session by itself.

 

POWER: THE ACCURATE MEASURE OF EXCERCISE INTENSITY

Power measures the force you are applying to the pedals and how often. It is physics and mechanics and there are no guess or external factors. Power meters measure the force your feet are pressing the pedals with and how often (cadence, the speed at which you spin the pedals).

Apply some formulas and you get how many watts (the most common unit of measure used by power meters) you are exerting. Its measurement is consistent and accurate.

Many fitness parameters are derived from this power readings resulting in a series of metrics, graphs and tables with precise data to evaluate a training session, assess performance improvements over time and plan specific workouts that will allow you to achieve your mountain biking goals, whether you compete and want to get first to the finish line or just hang out at the front of your group rides.

Most GPS Bike Computer companion apps will calculate and show the metrics for a training session that will allow you to accurately know the intensity applied. This is an image of a ride from Garmin Connect with the power derived metrics

And these ones from the Wahoo Elemnt app

With power analysis tools such as Golden Cheetah, you can analyze progress over time with graphics such as the PMC chart that plots how fitness is improving over time

and the Power Curve that allows to see where your strengths and weaknesses are. Are you a sprinter? Or are you more like a long distance rider? Are you training at the correct intensities to achieve your goals? All this can be seen in the Power Curve

While giving a look at what Golden Cheetah provides, I found a chart called Power vs. Speed Trend that shows whether your speed is improving at a given power level. In the long term you should be able to ride faster with lower power levels if your training is working. Interesting chart.

 

SUMMARY

The data derived from using power meter to train allows to accurately understand how you are performing in a training session, see your progress (or lack thereof) along time and properly plan your training sessions towards a certain event or goal you have in mind.

 

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