Expert Tips on How to Analyze Your Power Meter Files

Here is an interview with Dirk Friel, a co-founder of One of his jobs is to help professional riders and coaches to analyze data from power meters. Since one of the most important topics here on is power meter training, it is a pleasure to get some additional info from one of the experts into analyzing power meter files. This interview is quite long, but I hope you enjoy it, several good points are waiting for you! “I guess many pro riders have an SRM or PowerTap mounted (at least to look a bit serious) as a part of their bike equipment, but I’m not sure how many of these riders spend time analyzing their performances. Dirk, you have been working with several pro riders, so how will you describe their look on power meter training?”

Dirk Friel: “It seems today’s pros either embrace technology and will do anything to leverage the latest advances in hardware and software to their benefit, or they resist the new school of thought and hold onto the traditional ways of training. Some pros ride with a power meter just to give the illusion they are analyzing their performances when in fact, they’ve never actually taken the time to download their power meter.

I try to get riders into the routine of downloading and saving files daily as part of their job. Call me crazy, but if you are being paid to ride a bike, you should take it seriously and not waste your time. There is immense value in collecting and analyzing data over time. Maybe even more value than analyzing files daily. Spotting the historical trends and manipulating future training to take advantage of those trends is of huge benefit to those who take the time.” “One of the athletes you have been working with is Levi Leipheimer. He performs well in time trials and during climbing, but how did you help him to develop these skills, and how do you track his progress?”

Dirk Friel: “Let me clarify. I do not coach Levi and I don’t prescribe his training. That is the job of legendary coach Massimo Testa. My job is as a consultant to Massimo and Levi so they can analyze and view reports which track Levi’s progress. We’ve created reports within TrainingPeaks which are in essence a dashboard that compares this year’s data to last year’s. This provides a daily snapshot which quantifies Levi’s fitness, fatigue and overall form.

Levi can also spot when he sets new personal best records which directly affect his training intensity as performed in intervals. Levi is truly on the cutting edge of training analysis and is leveraging technology to gain an edge. TrainingPeaks is also the data management system which allows Massimo and Levi to efficiently monitor, analyze and plan training and racing.” “When you analyze results from a stage race, what key points do you look for in the power meter file?”

Dirk Friel: “There are a number of things a power meter can show you, but it all depends on the rider and their goals within the stage race. One rider may be trying to conserve energy during a stage, while another is trying to be aggressive or work for the team.

One of the primary metrics we track is a value called Training Stress Score (TSS). The Training Stress Score is essentially a way of assigning a value to a ride to quantify the amount of work performed, relative to the individual’s threshold power. The TSS value can give the athlete an indication of how well they may recover for the next day and beyond. Because TSS is directly tied to the individual’s threshold power comparing the TSS value between two riders is a good way of seeing which rider may have worked more than another. This is also very valuable when teaching young riders how to improve as a stage racer since the better stage racers know how to conserve energy for the crucial stages.” “Pro riders who are going to make top performance in time trials often visit a wind tunnel to optimize their aerodynamic position. Many readers here on are serious about their performance in time trials but don’t have the opportunity to save seconds in this expensive way. What would you recommend them to do to make their aerodynamics better?”

Dirk Friel: “With my little knowledge of aerodynamics, I can only advise getting a time trial helmet and aerodynamic wheels. I’m not an aerodynamic specialist, but I do advise riders get a yearly bike fit which has direct benefits when it comes to economy and the ability to time trial well. Racing with a power meter is also of great benefit for those riders who are still learning pacing strategies. Most riders start out too fast and blow up the second half of a TT. Proper pacing can dramatically improve your time trials.

Beyond that it comes down to flexibility to hold an aero position and targeted workouts to improve your muscular endurance, anaerobic power, strength and economy. Improving strength, flexibility and simply riding more in the TT position are probably the most under-rated ways to improve your time trialing.” “Training hard and dedicated is important, but reducing the amount of training before a big event is also a major concern. The perfect tapering protocol is a topic many riders have worked on for many years. Peaking at the right moment at the championship or specific stage race should not be based on many random factors, so heart rate and power meter data files offer a great opportunity to increase the success ratio of such projects. I guess you won’t show us the specific tapering protocol from one of the Tour de France heroes, but can you describe the basic principles you use to calculate peak performance when you analyze data files?”

Dirk Friel: “There are three basic metrics you need to track and be aware of fitness, fatigue and form. In general, we all know what these are, but most riders don’t do a good job of managing or objectifying them. A power meter with the proper software can allow the rider to track these metrics daily. The perfect taper will allow for the maintenance of your race-intensity fitness, reduce fatigue and allow the form to rise. I find
that most pros don’t allow themselves enough recovery time and therefore show up to important events with too much fatigue. It is hard for most riders to back off and allow fatigue to drop and their form to rise. It simply doesn’t matter how fit you are on race day. If your fatigue is higher than your fitness level then you won’t perform at your true potential.

This is why a power meter along with TrainingPeaks software can be so valuable. The TrainingPeaks Performance Management Chart will allow any cyclist with a power meter to track accumulated workloads over time and graphically view fitness, fatigue and form levels. Once you can do this, it becomes a whole lot easier to taper and peak.” “Planning a tapering protocol is also about looking in the mirror to see what has happened in the past. TrainingPeaks WKO+ offers a feature to measure acute and chronic stress. How will you describe this feature, and how is it calculated?”

Dirk Friel: “Chronic Training Load (CTL) and Acute Training Load (ATL) are the technical terms for fitness and fatigue. The last remaining piece to track is form which is also known as Training Stress Balance (TSB). To calculate the three metrics (CTL, ATL, TSB), the rider needs to first track daily Training Stress Score values. We then take the 42-day rolling average of daily TSS to calculate CTL, the 7-day rolling average of daily TSS for ATL, and the difference between CTL and ATL is the Training Stress Balance.

Training Stress Balance is what the athlete wants to see the rise as their highest priority event approaches. Ideally, CTL, or fitness, is near the highest of the season and ATL, fatigue, is low in order to have the form rise.

The screen shot of Silence-Lotto’s Mario Aerts Performance Management Chart which shows his CTL (in blue), ATL (pink), and TSB (yellow) between January and March 2007. You can see his TSB rose to its highest levels as he entered the Belgium classics season, which is exactly what he wanted. The three spikes in ATL are races in Australia in January, then a hard training camp and finally the third spike is the Tour of California.”

3 thoughts on “Expert Tips on How to Analyze Your Power Meter Files”

  1. Just a point of clarification: CTL and ATL are actually calculated as *exponentially-weighted* moving averages, not *rolling* averages as Dirk was quoted as saying. The end result is that CTL reflects primarily what you’ve done in the last ~3 mo (with more emphasis placed on recent training), whereas ATL reflects primarily what you’ve done in the last ~2 wk.

  2. So then should my constants for CTL and ATL be 84 and 14 days if it’s 3 months and 2 weeks??

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