Originally Posted by
osteoclast
You can bring your fitness to a peak (your peak) with a training program over 10-12 weeks.
Essentially intervals are stressful and sometimes us old guys are just not that motivated to suffer to that extent.
So how much can we improve our individual fitness? Depends on how hard we want to work and unless you're racing you're probably not going to be that motivated.
I suspect that's just one peak among many, potentially. Local maxima. To reach your full potential is likely to take more than 12 weeks.
I'll also take issue with the idea that only racing can motivate someone to do what it takes. Certainly it will inform your methods, but the only motivation? I think that there are many approaches, other methods and motivations.