In this issue Dr Mike Posthumus briefly discusses the benefits of using a power meter during racing.
In the April Full Sus Coaching Column (read it at www.fullsus.co.za/training-with-power/), I discussed the benefits of training with a power meter and provided some alternatives if you could not afford a power meter. Those of you who follow the social media trends in the bicycle industry will agree that we are entering a new age where power meters are becoming cheaper and thus more accessible to all. The launch of Stages Power Meters in South Africa has given several keen competitors a MTB power meter without a significant weight addition and at a very competitive price point. These trends will allow more and more keen competitors to not only train with power meters, but also race with power meters. In this article I will be briefly discussing the benefits of racing with a power meter.
When we talk about racing with a power meter, we instantly have the picture of Chris Froome staring at his stem in our minds. This is partly the reason for this particular article. Yes, we may be able to pace ourselves during a MTB race with a power meter, but we still have to ride over the obstacles the course presents. Therefore it becomes more complex. Due to the terrain MTB power data becomes extremely stochastic (highly variable) in nature. So if it is difficult to pace yourself using power on a MTB, what are some of the other benefits?
Recording the demands of MTB racing with a power meter is a perfect means of tailoring your training to increase the specificity of your training sessions (i.e. make your training more similar to the demands of racing). Analysing race power data will identify specific periods in the race of particular demand. Designing a training session, which mimics these demands repeatedly, is an excellent manner in which to improve your race performance. Note however, that these very race specific sessions should not replace all phases of your training. They should be included toward the end of a periodised training plan to add that cherry on top of the training adaptations you have already made.
Further, race data is also an excellent way in which to track and ensure progression. Post race analysis should consist of keeping track of your best 5 seconds, 30 seconds, 1 minutes, 5 minutes, 10 minutes, 30 minutes and 60 minutes of average power production during the race. Although these numbers may also be dependent on race terrain, trends over time should be used to establish if there is progression and importantly, to identify potential weakness. Furthermore, an important variable when analysing power data is normalised power, or NP. Normalised power, as well as other important key terms, is defined below. Normalised power should also be plotted and compared to similar races of equivalent durations.
Although I mentioned that it is very difficult to pace yourself using MTB data, you may use your IF (Intensity Factor) to ensure that you are not pushing yourself beyond what you are able to sustain for the desired. If your race is only 1 hour long, it may be realistic to maintain an IF of 1. However, if you are doing a race with an expected finishing time of 4 hours, do not try and maintain an IF of 1 for the first hour. You should base your targeted IF off previous races of similar intensity. Only experience with racing with power will assist you in pacing yourself using your IF.
Understanding Power metrics
Normalised power (NP): Normalised power is calculated from an algorithm to account for the random nature of power data and should be representative of the power you could have sustained with a constant power output. NP is more representative of the physiological demands of racing, when compared to average power).
Functional threshold power (FTP): Is the maximum constant power you can sustain for 1 hour.
Intensity factor (IF): Your IF is calculated from the fraction of your NP/FTP. You should therefore not be able to sustain an IF of >1.0 for more than 1 hour.
Training stress score (TSS): TSS is defined as your IF duration in hours. An all-out 60 minute time trial should therefore be approximately 100TSS. A mountain bike race may be anything from 100TSS (short cross country race) to 400 TSS (a tough day at the Cape Epic).