Go further per calorie – by going laid back
I’ve been putting in the miles on one of my upright bikes recently, ahead of a race where riding recumbent isn’t an option.
I thought I’d spice things up by swapping a session onto the High Baron, using the same PowerTap wheel to see whether I could make anything interesting of the data.
As I suspected, I was faster on my upright than on the High Baron. I wasn’t going flat out on either bike, since I’ve been doing ten or more rides a week – I was only subjectively investing the same effort on each. The outcome mainly reflects training on one bike (many hours) over the other (very little)… the specific effects of training shouldn’t surprise anyone.
What is more interesting is to compare the power I had to use to achieve each performance.
The route is a little under 25 miles with just over 1300ft of ascent (40km / 400m). Overall, I managed 17.5mph average for 230W on my upright, compared with 16.7mph for 168W on the High Baron.
I think there was more of a headwind on the High Baron ride, but since that only advantages the recumbent, let’s assume that wind conditions were the same:
Each recumbent mile cost 36.2kCal, versus 47.3kCal for each upright mile.
If I’d been racing myself, I’d obviously have won on the upright, but that’s just one way of looking at a performance. What if I was riding an ultra-distance event where I’m mainly limited by how much I can force myself to eat and how little sleep I can survive on?
For every 36 miles ridden on my upright I’d be an extra 11 miles further down the road on my recumbent (for the same effort) and once performance becomes limited by something other than absolute power (i.e. limited by fuel, fatigue, comfort, or any similar factor) that’s really going to tell.
Even on a 200km brevet my average power in the closing hour or so can be as low as 150-175W. I can achieve that on either type of bike, and then you’ve got to think of the next 200, 400, 1000km…
Convergence on hills, as expected
I’ve previously compared the performance of recumbent and road bike in ‘ideal’ conditions (flat without wind) and found a large advantage in favour of the recumbent (250W vs 150W for the same speed).
On the other hand, I’ve also previously bemoaned terrible performance on all-out hill climbs (the MetaBike took 36% longer), where absolute muscle recruitment and platform efficiency is paramount.
It would be expected then for a mixed route / mixed conditions performance to show much less advantage than the ideal case, depending on the proportion of time spent climbing and the proportion at high speed (where aerodynamics offers significant benefit). A flat TT would be very close to the 100W advantage shown in my earlier test, while a hilly ride would be closer to break-even, or perhaps to disadvantage the recumbent altogether, as in the second test.
Pleasingly this is the case for the rides in question: I was 0.8mph faster on upright for 62W extra, which is a much prettier picture than getting the same speed for 150W extra!
If I isolate the hillier section of the route I see 14.1mph for 350W (upright) against 10.6mph for 245W (recumbent). The lack of absolute power is dramatic, but again, only important if each second counts for its own sake (as in a road race or head-to-head hill climb).
Much more interestingly, the efficiency gap has closed right down, to 89.4kCal per mile (upright) against 83.2kCal per mile (recumbent). But…
The recumbent is still more *efficient* on a 10mph climb, albiet *slower*
Since so many people seem prone to equate slow climbing with poor performance it’s hard to emphasise this too much.
If you’re touring you’re hardly going to ride for four hours dead then stop wherever you are at the roadside. You probably have a destination and getting there a few minutes either side is not important compared with getting there in comfort or for less sweat and toil.
If you’re riding an ultra distance event, it’s not likely that you’re so strong that you can maintain high wattages for days at a time; it’s more likely that you want to get the maximum ‘bang for your buck’ when it comes to spending your body’s limited capacity for exertion.
Only if you’re racing over fairly short distances does absolute power outweigh efficiency.
If we buy into the hypothesis that recumbents reduce the muscle mass you can recruit by isolating your legs (which is one possibility) you can see that they really will start to shine as the miles rack up.
Other than the obvious (small sample size, indicative only…) the big caveat here is that I’m still measuring power at the wheel and not at the crank. This means it’s possible that one or other of the bikes is systematically under-reading the effort required. What if the much feared phenomena of drivetrain or frame losses mean that the recumbent really requires an extra 50W at the pedals to hit 250W at the cranks?
It’s impossible to answer this question without access to a crank-based meter at the same time as the PowerTap… if anyone has both and would like to run a few tests, get in touch!
For my part, I don’t really see how such a large difference can be accounted for through drivetrain losses: for starters, an idler that sucked out 50W would get as hot as an old-fashioned incandescent bulb, which is patently not the case.
Certainly there are many questions about recumbent performance that remain unanswered, but hopefully this chips away at another aspect of the problem (even if it raises as many questions as it answers!)
Any comments, as ever, gratefully received…