… Or why can't athletes maintain the same high / 'peak' level of fitness all the time?

… why does peak performance eventually drop off over time – despite continuing to train at similar levels?

How can an athlete be said to 'peak' too soon?

What's going on here?

(queue an ensuing mele of armchair sports physiology-babble from the STW massive)

you can maintain a high level – just not your absolute best – but the peak is usually becasue the structure of your training program is aimed at this. Also, in the terms you seem to be talking (pro-level), rest and (yes!) psychological factors have as great of a bearing on this as the physical effort. They are aimed at at end point/desired result; the peak!

Peak drops off, because all of the factors have to be in sync at the same – rest, base fitness/skill level, lack of injury, positive mindset etc; it's hard to keep all of these things at the required top level for an extended period – more training = less rest, competitive focus = ignored social life, etc and vice versa, which creates a balance that is hard to maintain in a real life situation.

Peak too soon is just getting the structure of your training/focus/rest/whatever you in particular need program/schedule, "wrong" and therefore not being able to maintain the above mentioned delicate balance through to the intended/desired end point in time (eg final or champ. race, etc) hence too early, or not having it all in place in time – not reached peak

Yeah what Langy said. A peak requires a lot of training followed by a taper, the more you prolong the taper the more your fitness can drop off.

If you trained really well, did everything right, no injuries/illness etc, then had a really easy week going into a race you'd be nicely rested and probably go well. If you then took another week really easy and raced the next weekend you'd start to lose fitness. Another week and it'd get a bit worse etc etc.

It's not really rocket science!