Can you train into deeper fatigue as you get fitter?

Say on Strava’s fitness and freshness, or something similar, you train to -40 fatigue then take a rest. Later can you train to -50. Then -60 etc, as you get more fitness/endurance etc.

Or is it sort of relative and you’ll always feel roughly as poor at whatever number it is, even if you’re a pro compared to a novice?

I know it’s not an exact science that chart on Strava but I like it, and it tallies well for me in performance terms. I usually stop around mid -40s. But I’m thinking this week to push it deep into -60s as weather will be great and it would be a shame to miss out.

I apologize as I don’t know the exact terms Strava uses, but and Training Peaks (I think), use fitness, fatigue and form, so I will use those. I think it is easier if your ‘fitness’ is lower to get a more negative ‘form’. form = fitness - fatigue. Say your ‘fitness’ is 20, then you only need a 60 ‘fatigue’ to get the -40 ‘form’. If your ‘fitness’ is 100 you need to hit a 140 ‘fatigue’. I guess at the unrealistic end, a ‘fitness’ of 0 makes any kind of training take your ‘form’ drop below zero and would be the easiest.

Personally, I cannot stand the fitness / fatigue / form nomenclature. I understand why it came to be, namely because of trademarks on CTL/ATL/TSB, but I think it really confuses the topic. My perspective is that a high chronic training load does not mean you are ‘fit’, it means you have a high chronic training load (relative to your FTP.) Does having a ‘fitness’ of 100 with a 200 watt FTP mean person A is ‘fitter’ than person B with a ‘fitness’ of 80 and a FTP of 300 watts (all other things equal)? I don’t think so, I think it means person A has a higher relative chronic training load that person B.

I tend not to have TSB/‘form’ drop below -20 - -25 at the most. My perspective is that if it is too negative it means I am ramping up the training load too quickly relative to my long-term load, and that is usually not sustainable for me and can lead to overreaching (TSB = CTL - ATL.). A training camp like week might get me below -25 there but I am not able to do those often. I can’t imagine how my body would feel if I hit -40 or below.


There is always talk about “going deeper” in endurance events as a combination of mental and physical effort, which can definitely be trained on a mental level. I wouldn’t pretend to know the science of the physical side of fatigue.

But I can tell you that the Strava Fitness, Fatigue and Form are very flawed. For the last two years my “form” has read as low as 80 after rides and almost never above zero. The only period of staying near zero was when I was on the trainer all winter.

Any time I do a long ride all the Strava metrics take a massive jump. Especially with HR only based data (power helps a lot) time is much too large a factor in the calculation. Spanish Needle and going for a 2 hour mtb ride with some friends at very casual speeds have the same effect on fatigue and form.

Last year I did a completely flat, no wind century with Max HR at 125bpm but it took 5:30. In the middle of my Marathon XC training it was one of the easiest weekend days I had, but checking on Strava my form went down 57 to -61 that day. Later the target race came and after an all out 3:47 on the bike Strava shows form down 71 to -67. This time I felt gassed on the bike for a week and a half recovering afterwards, but looking at Strava Fitness, fatigue and freshness" you can’t tell the difference.

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Many people find it more realistic to set your fatigue as a percentage of your fitness as opposed to just a straight calculation. This is especially more relevant when your fitness number is relatively low.

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As an example, in May I did 10 stages of the RGT Giro, loads of sweetspot rides, several over 90 minutes at continuous sweetspot, it was hard. My chart showed me nicely in the “green” zone on raw figures but with it set to percentage of fitness I was way deep into the red area consistently for about a week. For me this was more representative of how I was feeling.