Looking At Power Outside vs. Inside?

Winning the watts game: more than just blind grinding… it’s understanding the key differences between dynamic, outside road conditions and the controlled, almost clinical environment that indoor interval sessions afford.

“Saved up and got that power meter finally. How do I go about using it on my outdoor rides now? I want to know, at a basic level, the most important data point when looking at outside/road-derived data and the indoor session-derived data, and how to utilize it.”  

- Samuel, who recently bought and installed a power meter on his road bike
  • A great question, as it addresses concerns that are becoming more common – as the prices of powermeters have been decreasing while availability has been increasing too.
  • First, understand that if you cycle with two different power meter systems (one on your bike which you typically ride outdoors, and the other via the Computrainer/PerfPro system in Athlete Lab, for instance), you are not necessarily going to get the same set of data for a given workout. that in itself is not a problem; what matters is having accurate calibration of your power meter to provide you with consistent data sets.
  • Outdoors on your own bike, learn how to do calibration or ‘manual zeroing’ before you start each ride. Because power meters are very sensitive to temperature changes, it is wise to double-check this if you are riding on a particularly hot/cool day, or have taken your bike for riding overseas in a climate which is much different to your typical ‘home’ climate.
  • Riding indoors, you will get workout sets which require very precise changes to effort, duration, cadence, and so on. Outside, you are subject to a host of factors such as variable wind speeds/directions, inconsistent gradients,  differing granularity of road surfaces (from super smooth to cobblestone-like), and of course the natural ebb and flow of the peloton (depending on whether you are in the draft or taking a turn out front). Riding in an urbanized setting adds even more factors in the form of reacting to traffic lights as well as motor vehicle drafts and buffeting.
  • Take particular note of Normalized Power (or NP) as you progress through your workout (whether indoors or outdoors). It is not the same as average power – in fact, you will end up with much higher numbers generally. NP is NOT the quotient of your wattage divided by the time you spend pedaling (and cutting out the instances where you are not pedaling/coasting); it is more complicated than that, but what it essentially gives riders is the measurement of approximating what a ride’s effort would look like (at a constant output) if all the peaks and troughs were removed.Peaks and troughs are fairly common on indoor workouts, depending on its nature. For instance, sprint-focused intervals have VERY DEFINITE peaks and troughs where the rider’s output dips to almost zero, whether intentionally or otherwise following a big peak effort. In contrast, a long endurance time-trial simulation indoor workout would afford very little peak or trough variations.But get this: peaks and troughs are even more prevalent in an outdoor ride. The sum of the factor mentioned above all conspire to give the rider what would look like a very erratic power output graph, even for someone who is riding well within his capacity on a very steady cadence and perceived effort.Taking NP of each hard effort/interval done outside into account helps you analyze better without being put into a situation where you are analyzing the wrong data (eg: average power, which usually comes up as woefully lower than what a solid FTP test/figure might suggest). Do study the settings of your powermeter in more detail to see how you can capture the 3, 5, or even 10-second average, especially if your intervals outdoors cover long efforts (sustained hills, long-duration aerobic intervals, even your recovery rides) on terrain that is high-traffic, has lots of corners, or requires jittery, close-in peloton-style riding with a cycling group of varied ability. You may experience none of these when indoors, but taking them into account in your power analysis for outdoor training will give you a better perspective and basis for comparison of your training progression FAR BETTER than just focusing on indoor data sets or outdoors data sets in isolation.