[Schroedingersat]

> So recruiting more muscle groups really doesn't help. What does is increasing oxygen intake, and this is where recumbent bikes come in. The laid back position opens the thorax and increases effective lung capacity. As well as reducing air resistance, except that that's a very subtle thing that mostly depends on the rules governing the sport in question (fairing on bike and kayak, for example, are variously restricted or banned in most relevant sports).

Recumbent riders generally have much lower peak power and ftp but higher sustained so VO2 differences wouldn't explain it. The main attribution I've seen is aero and marginally less muscle power used for motions that aren't related to pedalling.

[Psychlist]

My limited experience is that it's easier to recruit more muscles on an upright, so your peak power can be higher. In my 30's I would hit double for a 30s trial on an upright vs a recumbent (last time I had a decent power meter was in my 30's). But over 5 minutes the recumbent was better even if both were fixed to stands. So I don't think it's the balance issue.

For an hour or more the recumbent wins just for comfort, and unfaired records it wins on air resistance (that's why the UCI banned them, it let povo scum beat gentlemen athletes). But then the UCI doesn't have faired records... it's only the IHPVA et al that make that distinction.

Interestingly the PBP etc records (we don't have records, this isn't a race!) are all uprights AFAIK. But that's xenophobia rather than technical skill from what I know. And the Round Australia record is an upright, largely because no-one on a recumbent has been inclined to attempt it. RAAM is held by a bent (https://en.wikipedia.org/wiki/Race_Across_America#Records).

[bmj]

Recumbents are notoriously difficult to ride as the grades get steeper. Upright cyclists have the advantage using different body positions (i.e. standing), but 'bent cyclists can't do that. On the steepest grades, it can be a challenge to even keep a 'bent's front wheel on the ground.