Introducing an athlete to the process of training with power can be arduous. The devices themselves require a learning curve to set up, calibrate, and utilize. Once that is out of the way, then the real fun starts: uploading the data to the variety of software platforms available and determining what utility it has.
Once I teach the basics and the athlete understands the process, then it is a matter of interpreting and explaining the data. Although power training “zones” can be established, just like heart rate zones, the real accuracy is derived from using the athletes own “personal bests.” The more popular analysis software used to analyze power data scans each uploaded workout to determine if the average power for a particular length of time exceeds the known value for the athlete. This is called their “Mean Maximal” or “Critical Power” for that period of time. For example, an athlete may have a 30 second Mean Maximal power value of 473 watts. During their last ride they exceeded the average power of 473 watts for 30 seconds with a value of 486 watts, which now becomes their new Mean Maximal 30s.
Instead of testing periodically to determine zones based on a percentage of a test average, each work out is an opportunity to set a new personal best for a time period ranging from 5 seconds to 3 hours. Workouts can then be created and prescribed based on the athlete’s known performance envelope (ex. “perform a 20 minute interval at your CP90 min. power level”). The athlete’s “high bar” changes much more frequently and it is a more accurate and adaptable way of coaching and training. Personal bests become both the carrot and the stick to achieve new levels of performance, often squeezing that extra bit of potential out of the athlete.
There is one caveat, however, in that power training can frustrate the athlete, especially those driven by numbers. Fitness is a slow process that requires patience, and it is important to understand that new power levels are not set every day, or week, and sometimes not even within a month. When an athlete begins training with power, every work out will set a new personal best but as they progress, the bar becomes progressively higher. Personal bests are only be achieved when the athlete is sufficiently rested and/or tapered, which is one of the reasons race power data is so important. An athlete may try very hard to hit a number that is not achievable on a particular day. It is vital to set the level of expectation for progress when training with power. Personal bests may only be set in peaking phases, but that does not mean the athlete is not making progress on another level or fitness substrate.
By comparison, the power ranges that are derived from a heart rate-based workout are considerably broader and less accurate. For instance, a zone 3 heart rate workout may produce a much wider wattage range when compared to a CP90 work out. This can be used advantageously. I like to give my data obsessed athletes a break from highly structured and targeted training at key points in the season. By switching to heart rate, especially for base aerobic work outs, I give them more wiggle room and less structure. They can still upload their power data and it is still useful, but we will use broader heart rate ranges. You cannot press an athlete for new performance levels year round, and when it comes to using personal bests a more prescriptive approach is often better.