The Power Meter Handbook: A User’s Guide for Cyclists and Triathletes

performance compared with others. Your CTL at any given time shows only your trends—how you are doing now compared with previously.
    Having such a tool allows you to manage your training by controlling how fast the line rises or falls. You can watch and control trends using it. When CTL rises, you are undoubtedly becoming more fit because you are coping with more stress. But you are also becoming more fatigued.
Fatigue
    You should now understand the relationship between TSS and fitness. As you increase your training workload, as reflected by an increasing CTL on the Performance Management Chart, your fitness improves. Of course, these same increases in TSS per day are also going to make you more fatigued. Greater training workloads make you tired. So if fitness improves with a rise in TSS per day and fatigue also increases as TSS per day rises, then we can draw the conclusion that both fitness and fatigue follow the same trends. In other words, if you train hard, you will become both more fit and more fatigued. If you decrease your training workload, both fitness and fatigue will also decline. That may seem obvious now, but as we get deeper into this, you may question that logic as it applies to race preparation. But stick with me, and I’ll show you that the truth of this statement does not contradict your experience.
    The Performance Management software calculates daily data points for fatigue in the same manner as was done for fitness (CTL). Only instead ofthe calculation being based on a 42-day rolling average, it is based on 7 days (again, this is a default setting in the software and may be changed). The reason for this metric is that fatigue occurs and diminishes rather quickly when compared with fitness. The day after a hard ride, you are not able to measure changes in fitness since they are so small, but you can, indeed, sense fatigue. There’s no doubt that you’re tired. But a day or so later, after some recovery, the fatigue is almost gone. So since this calculation has to do with brief periods of time, the software calls this fatigue the “Acute Training Load”™ (ATL).
    CTL and ATL sound very important, but I refer to them instead as fitness and fatigue when I discuss performance management with athletes. While these terms aren’t precisely fitness and fatigue in a biological sense, they are good indicators of what’s happening in the body and much more easily understood. So for our purposes, CTL = fitness and ATL = fatigue.
    Figure 7.2 illustrates the fatigue (ATL) for the same rider whose fitness (CTL) was described in Figure 7.1 . Notice how much more “spiky” the rider’s fatigue line is than the fitness line for the same period of time. Again, that’s because fatigue occurs rather quickly and to a greater magnitude, so a rider is very aware of it in contrast with the slower response of fitness.
    By overlaying the rider’s fitness (CTL) and fatigue (ATL) lines, we get a clearer picture of what was experienced over the course of the entire season. This is done in Figure 7.3 . Whenever the fatigue line is above the fitness line, we know that fatigue is quite high. Notice the huge spike in fatigue in mid-to late June at the same time that fitness is steadily rising. We know from this that the athlete was training very hard during this 2-week period. Fitness was rising, but fatigue was extremely high. That was preceded by a period of no training at all in late May, as can be seen by the rapidly falling fitness and deeply dipping fatigue lines. In fact, this chart describes quite well what was going on with the rider over the courseof an entire season. It’s the backdrop for a long story the athlete could tell us about that season. And yet all it represents is data downloaded from the power meter every day.

    If you fail to download workout data, then this chart and others are useless. You must be dedicated to doing this for every ride without exception. If there are days that you can’t download because of other commitments, don’t fret. The head unit stores the data, which can be downloaded later. It is capable of storing several such workouts. How many depends on which head unit you have, how it is set up, and how long the rides were. Consult your user’s guide for the details of your device.

Form
    The Performance Management Chart can also be used to help you peak on race day. Peaking, sometimes called “tapering,” is a periodization method in which duration is reduced while