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The Relationship Between Fitness and Fatigue in TrainingPeaks

BY Joe Friel

Are you constantly fatigued? Here's how you can use the Performance Management Chart to tell if you are overreaching or overtraining.

Many successful endurance athletes are type-A personalities. They are driven to succeed. While this is necessary to some extent, too much drive and motivation can lead to disastrous training and poor performance. This is evident in the following question that I recently received. The athlete, a cyclist, understands a lot about the intricacies of training. His question uses several terms common to power-savvy cyclists and triathletes who use power meters (or GPS devices for runners). Here’s a quick reference so you can understand what he is asking in case you don’t train with power (or a GPS for running):

  • Chronic Training Load (CTL): A rolling, daily average of how much training stress an athlete is managing. The more stress he/she can handle the greater their fitness. So CTL is a good proxy for “fitness.” If CTL is increasing then fitness is generally increasing also.
  • Functional Threshold Power or “Pace” in running (FTP): This is how much power (pace) a rider (or runner) can maintain for an hour. It’s similar to lactate or anaerobic threshold power (pace). Increases in FTP indicate an improvement in aerobic fitness.
  • 1-minute max: The highest max power (or pace) one can maintain for a minute. This is another indicator of fitness.

The question:

I’m a big fan of your blog. I’m having trouble understanding fatigue and recovery. By definition, I need to experience fatigue to gain fitness, but how much fatigue should I “feel” day to day? I’ve been increasing my CTL in 3-5 week cycles, resting a little more for 1 week, allowing a little loss of CTL. Then I hit it again and increased my CTL…. The problem is that my perceived fitness and actual fitness are not getting better. I just feel tired. Heavy legs, not making gains in my FTP, I’m stagnating! My FTP is not in decline, but the numbers I’m putting out seem to require more perceived effort. My 1-minute max has been in decline; at one point, I was able to maintain 550 watts for a minute, and now I’m at 440 watts. The question I have is, how should I feel during training, because quite frankly, I feel like “sh-t”…. and I don’t think I’m supposed to. The other option is that I’m just not cut out for endurance sports because I can’t take the suffering. I just feel weak!

My answer:

First of all, everyone is cut out to be an endurance athlete to some extent. That’s our inheritance as homo sapiens. We’re hunter-gatherers by design—slow sprinters compared with the rest of the animal world but better than the others at endurance. Some of us just have more endurance genes and opportunities than others.

What you’re experiencing is not unusual at all for highly motivated athletes. It’s common for us to always seek our limits. Since you seem to be using the Performance Management Chart, I’ll give you a suggestion that may help you regulate your training to avoid extreme overreaching.

First, some overreaching is necessary to improve fitness. You seem to understand that, given your reference to fatigue being required to improve fitness. However, overreaching and fatigue can accumulate too quickly for the body to adjust and adapt to them. The body functions best when the rate of overreaching is gradual. I suspect yours is overly aggressive.

The rate of overreaching (and therefore “hard training”) is probably too high when your CTL is increasing at a rate greater than 5 to 8 TSS per week.

  • If your absolute CTL numbers are relatively low (let’s say, around 50 or less), then an increase of 7 or 8 in a week is probably a bit too much. Keep it lower than that.
  • If your absolute CTL is higher (around 80+ we’ll say), then a weekly increase of 5 or 6 is pushing the limits. You may be able to manage such a rate of CTL increase for one week and get away with it (some can’t), but the longer you keep that going, the deeper the fatigue hole you dig.

After 2 to 4 weeks of increasing your CTL by such excessive amounts, you are likely to be toast. You’ll be in the early stages of the overtraining syndrome. That will be marked by symptoms like:

  • relentless fatigue
  • poor training performance
  • lethargy
  • low motivation
  • bad attitude about life in general

If you keep pushing it beyond this fatigue, you’re likely to experience full-blown overtraining, which is similar to having a disease such as mononucleosis, chronic fatigue syndrome, or Lyme disease. It isn’t pretty. And it may take you weeks, if not months, to shed the overtraining symptoms.

By keeping the rate of your CTL increase below the numbers suggested above, you should be able to train steadily while making fitness gains and avoiding the downsides.

It may also be that a 5-week period of training in which CTL steadily climbs is too much for you. I train most of my athletes with 2- or 3-week periods before they rest. And regardless of your usual period length, if you are overly fatigued then you should recover immediately regardless of the plan. Training plans must be flexible to be effective. Doing workouts just to satisfy the plan is doing it backward.

Of course, there are other stressors in our lives besides training. Supporting your family, working a lot of hours, having a physically or emotionally stressful job, experiencing lifestyle stresses such as relationship or financial difficulties, and having other pressing responsibilities can also lead to what may be interpreted as overreaching. If this is the case, then training must be reduced regardless of your weekly rate of CTL increase.

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About Joe Friel

Joe Friel is the author of The Triathlete’s Training Bible, Your Best Triathlon and other books on training. For more information visit his website at You can also view and purchase Joe’s training plans on TrainingPeaks.

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