[pro_zac]

They never account for fatigue. On long descents your neck and arms will get tired. The downward back is especially stressful on your neck to hold your head so you can see forward. This means changing to a less aero position to rest your neck and arms. Some positions may be less aero but also put less strain on a rider that may be 4 hours into a race already.

[chrismckleroy]

So true. Which really makes that Pantani position solid, as you are resting chest on seat and eyes are forward.

[Ericson2314]

Yeah when mountain biking something extra steep, Pantani is the only way.