Gaining fitness as someone who was previously trained

Let me explain a hypothetical scenario to help me ask my question:

  • Person A used to hold a good level of fitness, doing some hard sportives and sustaining periods of 200+ miles a week for around 5 years.
  • Person B has never been this fit.
  • Both people are currently lacking in fitness and both around 25kg overweight

Ignoring technique and prior knowledge, if and both people were to start the same regieme of exrcise and good diet at the same time, would there be any difference in their progress based on one having been very fit before?

Person A should develop faster I think. The half life of muscles is large and they had more when they were fit. Like everything in life though it won’t be as simple as that and person B might have more motivation currently.

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I’ve done that experiment , at least the detrained athlete part! IMHO, once you have fitness, even if you lose it over time, it comes back faster than for someone starting from scratch.

This is a function of some permanent changes that occurred the first time around and also the concept that a decent part of fitness involves your nervous system in essence learning a skill in terms of muscle activation, etc and those “skills” comes back faster than starting from scratch. And, there is some hint that once trained, muscles retain an enhanced ability to gain strength back faster than untrained muscle. The concept of skeletal muscle memory: Evidence from animal and human studies

Also, simply being experienced with the process of training can make the experienced but out of shape athlete much more efficient in training than a newbie giving them what can be a huge advantage so you can’t discount that.

So, generally speaking, one should be able get fitness back faster than someone else can develop it from scratch.


I’d imagine the individual details are pretty variable, but my understanding is that it’s generally easier to get back to where you were the second time around.

As an anecdote: I was a fairly competitive runner for a lot of high school before dropping out due to an eating disorder. Ended up being 5+ years of me being significantly underweight and hospitalized frequently, so pretty much entirely sedentary along with periods where I was essentially bed-bound for several weeks at a time. Returning to a healthy weight was basically just restoring normal body fat levels, so can’t imagine there was much in the way of muscle left there. I think I matched my half marathon PR within 6-8 months of resuming running, and qualitatively I think I improved a lot faster and started from a higher ‘baseline’ of endurance the second time around. Started training with a club early on and got a lot of comments on that!

As @STP said, I think having some experience with the process was a big one- once I’d built up some mileage and confidence I moved pretty quickly into training for specific targets rather than ‘just running’ which tends to be how most beginners approach it. I was also able to sidestep some common mistakes and had a general idea of what worked for me, so it kind of felt like slotting into a familiar routine despite how long it had been.

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Person B could also have a never trained world class VO2max and in six months be running circles around Person A.

I raced road for 5 or 6 years and never got past cat 4 in a very competitive district. Many times I saw new guys come in and in one year jump two categories. They didn’t have the riding and racing skills but they had a better engine.


All else being equal, prob person A. Tho, person B might be just a stronger person / higher natural ability. Your heart / cardiovascular system definitely undergoes considerable changes holding high training loads for years.

I did 4 years structured cycling training and was around ± 5w/kg ftp for the last 2. I then took 2-3 years with no training or no more than 50-75% of old volume inconsistently (other life priorities).

I have been continuously training for about 2 yr now and have regained the old fitness with slightly lesser ftp but higher <10min power levels. Took me about 9months structured to get back to around the old level. This is from early 20s to late 20a/ early 30s tho.

Second this. I personally went cat 5 to 3 in one road season, 3 to 1 in one mtb season, and from 3 to 2 in one CX season (starting at cat 3 based on road license). I’m a pretty good bike handler but I rarely won or placed well based on tactics / skills. Usually just aerobic engine. This was racing in NE / mid Atlantic so I would say a pretty competitive field

Really depends on the genetics of A and B. At this point in time you don’t know how B responds to training. They might have superior genetics and improve their fitness at a faster rate than A given the same training programme.