I often hear people talk about peaking on an annual basis. It seems to me that in order to have a view of training wherein you peak out like this, you have to have a few assumptions.
1) An athlete can attain maximal fitness for performance only for a short period of time
2) One's performance will decline after reaching this "peak"
It seems that an accompanying assumption might be that overtraining results in peak fitness, which would explain the seemingly unsustainable gains.
One related idea is that many cyclists live in a place where they can't ride year round. Some riders however, do live in livable winter environments and ride year round without extended periods out of the saddle.
1. In your own experience, do you believe in "peaking" regardless of the scientific literature?
2. Do you live in a place where you can ride year round?
3. Are you aware of any scientific data that suggests humans make unsustainable gains in cycling performance?