Tri v Road bike - power question

Triathlon Forum
1

So this stems from what someone said in the Lake Placid thread regarding people climbing best on the bike they trained the most on. I remember reading some people say that you make more power from a position further back, like a roadie. If climbing speed is purely related to power to weight ratio, and you control for weight (same rider), would it be safe to assume that if you climb faster on the tri-bike your making more power on the tri-bike?

I guess my question is if one trains on the tri bike more/exclusively, will that person make more power on the tri bike than on the road bike?

I know that when I was riding the tri bike alot at the end of last season I felt I made better power on the tri bike, now I haven’t really been on the bike for 3-4 months and I feel stronger on the roadie. Should I do alotta time on the tri bike again to get more comfie in time for my first race (Wildflower)?

2

I think the greater power most people get from a road bike is due to position. Most tri bikes have a seat angle of 76 degrees or steeper. This position seems to recruit mostly quadricep muscles.

A roadie seat angle of 73 degrees or slacker tends to use not just the quads, but also the hamstrings and glutes. But it’s much harder to get a low front end with this position and heavy recruitment of your hammies and glutes may not be a good thing if you have to run before or after.

3

Fluffy – your instincts are correct.

One more time for those not paying attention: There is no such thing as a position on a bike that makes “more power” than another, equally acceptable position. Forward, backward…doesn’t matter. However you have trained the most is the way you will produce the most power. (the caveat being that you need to be sitting on the bike in a way that allows your lungs and limbs to operate well – which is a rather broad range of possibilities.)

I think people keep buying into old Euro myths about this stuff. Don’t forget – there was a myth that lasted for two generations that smoking helped cycling because it “cleared out the lungs”.

Let’s think through this logic: If a given position is “most powerful”, wouldn’t one want to ride that position all the time? Why be powerful on hills and weak on flats. And – it has nothing to do with the fact that the bike is tilted up a degree or three. This has been studied, and muscle recruitment does not change with hill slope.

As for “sitting back and recruiting bigger muscles”…cycling is not strength limited, so the size of the muscles involved has zip to do with power generation. I think that, as their cadence plummets, people want to sit back and pull on the bars to get the pedals around. This is a reflex that is not optimal, and would be avoided simply by proper gear selection. It’s also driven by the continuing misconception that cycling is a strength sport. It’s not; it’s an aerobic power sport. I bet I am WAY stronger than Heras, and he’s a wee bit more powerful than me on a bike.

So yes, race the bike you trained on the most. You will climb the best on that bike. If you’re going to race a tri bike at Wildflower, then train on that bike.

It’s all about specificity.

4

Isn’t it true that the rider’s ‘position’ is the same?

With ‘steep’ vs ‘shallow’ they’re simply rotated to a different postion around the bottom bracket. Now if your shallow road bike position entails a smaller hip angle, then I would tend to agree with your statement a bit more.

5

“Let’s think through this logic: If a given position is “most powerful”, wouldn’t one want to ride that position all the time? Why be powerful on hills and weak on flats”

I agree for the most part but with one caveat. How much power can you afford to sacrifice for better aerodynamics? I did a 30 min TT on the computrainer a couple weeks ago on my road bike riding mostly on the hoods. I have been playing around with my position on the tri bike for a while and based on some of the info on this forum have gone more forward and lower in front. I feel like I have gotten to the point where my position is pretty aero. Last night I did the 30 min TT on the Tri bike and was surprised to find that at the same HR I was putting out about 20 watts less. My question is, despite the lower output, will I be faster based on the better aerodynamics?

6

“Isn’t it true that the rider’s ‘position’ is the same?”

Theoretically, yes. But I would invite you to experiment and see what you find. I do 80% of my riding on a 73 degree seat angle road bike and 20% on an 81 degree seat angle tri bike. After a long ride or a hard set of intervals on the tri bike my quads are always sore but my hammies are relatively fresh. I can’t explain it, but my empirical evidence seems to support my theory.

But I’m not a physiologist and my n=1.

7

I had a similar thing happen to me. I lost 25 Watts in my lactate testing riding in a very aggressive aero position compared with previous tests on my road bike. In addition, my pedal stroke went to crap…spiking the whole time, whereas I have a very fluid pedal stroke in the road position. We determined that assuming a 10% reduction in frontal surface area by changing to the aero position, a 15 Watt advantage would be anticipated from aerodynamic positioning alone. That still put me at a 10 Watt deficit at L2. Needless to say, I made some modifications to my aero position that day. I also plan to ride my tri bike more and practice riding my PC’s in the aero position.

8

How much power can you afford to sacrifice for better aerodynamics?

No specific answer; one must do the math or some trials.

I rode a 4.1 mile loop circuit about a month ago. I did 3 repeats, each came out to exactly 230 watts. Average speed on each was 20.6, 20.5, 20.6, respectively.

I did the same circuit two weeks later after lowering my bars two inches and bringing my saddle forward a little to compensate. This time, I did 4 continuous loops as part of a duathlon, and my power was lower as a result. The four laps averaged 210 watts, and ranged from 208 to 212 each. My average speed was 21.75 mph.

Weather conditions were virtually identical. I zeroed the Powertap before each ride, rode the same tires/wheels and used actual stopwatch time and the start-finish lines as pace gauges on each. The only difference was a lower frontal area.

So, I gave up 20 watts (intentionally), yet went over a mile an hour faster. So, we can give up watts for better aerodynamics. Not without limit, of course. It depends on the specifics of what is being changed and by how much.

9

Julian, didn’t you just contradict yourself?

Post # 3

"There is no such thing as a position on a bike that makes “more power” than another, equally acceptable position. Forward, backward…doesn’t matter. "

Post # 8

"I did the same circuit two weeks later after lowering my bars two inches and bringing my saddle forward a little to compensate. This time, I did 4 continuous loops as part of a duathlon, and my power was lower as a result. "

10

Julian, didn’t you just contradict yourself?

I wasn’t clear – when I said “power was lower as a result” I meant my power was lower because I was riding at lower effort because I was doing (1) a duathlon, and (2) four continuous laps instead of three individual ones with rest breaks.

Sorry for the confusion. I *intentionally *rode at 210 watts on the second ride, as a choice of race strategy.

However – I do think my absolute power level is slightly lower right now in the new position because I haven’t adapted fully. (The main problem I’m facing is the fact that my aerobar arm pads are closer together, and I’m having trouble making that work. I’m getting neck cramps after two hours. The leg power is there, but my comfort level is still catching up.)

A change in position can lower our power for two reasons:

(1) It’s a really bad change. For example, if I lowered my saddle four inches, my power would drop and stay dropped. It’s outside the “reasonable range.”

(2) Change requires a little adaptation. If you paraded a series of cyclists through your ergometer lab, you would find that nearly all of them put out the best power in the position they came in on. Change almost anything, and their power drops. That’s why Computrainer bike fits are pointless. Most of us will acknowledge that we arrived at our current bike fits a little at a time, over a few years. It’s iterative, the process being: (a) change something; (b) adapt to it; (c) measure results; and (d) repeat. It’s quite common for absolute power levels to drop a little at first. This is also why it’s a bad idea to switch bikes or bike position on the eve of a race.

11

What folks seem to be saying is that it’s not simply a question of position (the triangle created by the relationship between saddle, pedals, and hands/arms that can be rotated around the bottom bracket to make tradeoffs between comfort and aerodynamics). The relationship of that position ‘triangle’ in relation to gravity influences sustainable power. Am I summarizing this right?

12

The relationship of that position ‘triangle’ in relation to gravity influences sustainable power. Am I summarizing this right?

I would agree that John’ first post above implies that. But, I think something else is at work for him. If we “freeze” the basic triangle, and then rotate it forward (which is the basic presumption of Dan’s FIST protocol), we can ask whether our muscle recruitment really changes. I think that, in real life, we don’t really “freeze” the triangle – we end up making other subtle changes to the angles.

Back to the “frozen rotation” idea. The best way to test the hypothesis is to take somebody’s existing bike and simply rotate it in a stand hooked up to an ergometer. Wire up the athlete with muscle activation sensing electrodes and have at it. We can now test whether the simple orientation of gravity changes how we pedal.

In fact, this has been done (I had a few pubmed cites at one point, but can’t find them now). I looked into this question because I was trying to figure out why we all tend to pedal more slowly on climbs, even when we have additional gears to reach for. I thought maybe it had to do with our changed orientation to gravity. It doesn’t. The muscle activation studies show no difference in muscle activation when the orientation to gravity is changed on the bike.

There is a reason we pedal more slowly on climbs, but it has to do with gear ratios, not the slope of the road.

13

" Last night I did the 30 min TT on the Tri bike and was surprised to find that at the same HR I was putting out about 20 watts less. My question is, despite the lower output, will I be faster based on the better aerodynamics? ’

I would say yes you’d be faster in the aero position. In fact it can be calculated based upon the amount of power to over come drag.

I read something recently (unfortunately forgot to bookmark it) where it was determined that a group of riders produced more power sitting up in hybrid bike type position than on a racing aero position. However, the authors determined that this would be a much slower riding position due to the aerodynamic drag.

14

JustCurious wrote: The relationship of that position ‘triangle’ in relation to gravity influences sustainable power.

I think this COULD be true. For example, if you were upside down, you wouldn’t need hip flexors firing much, if at all. Also, the increased lymphatic flow from your legs might keep the edema in the interstitial spaces at a very low level…decreasing the distance between the capillaries and the mitochondria. This would allow for quicker diffusion of molecules, such as oxygen, and removal of waste products. So, maybe inverted would be the best position.

But, inversion will only be better for power if there is a greater advantage due to the increased lymphatic flow rate than the disadvantage of decreased blood flow rate to the legs due to the energy required to pump blood uphill.

As far as 73 degrees vs. 81 degrees…I do think there are body types that do better in one style of pedalling vs. another. People with big gluteal muscles may do better when they can get their heels to drop early in the power stroke…theoretically, you can do this at either 73 degrees or 81 degrees…but, you’ll have to practice.

On a road bike, I used to find myself sqeezing the back of the saddle with my thighs when really pushing hard…I felt it kept me anchored. As I would rotate forward, perhaps I’d have to slightly rotate my saddle forward, too, in order to have this same anchoring point. If you do tilt your saddle forward…you’d darn sure better be comfortable in that position, because you won’t be able to sit up straight for a change! BUT! I don’t find this sqeezing to be used when I’m as far forward as I can get, because I’m time trialing, and I don’t use big power when time trialing…that kind of power I used only big acceleration on a buildup to a sprint, or for trying to keep up with the skinny guys on the climbs. Again, not a concern to me in a time trial.

15

Back to the “frozen rotation” idea. The best way to test the hypothesis is to take somebody’s existing bike and simply rotate it in a stand hooked up to an ergometer. Wire up the athlete with muscle activation sensing electrodes and have at it. We can now test whether the simple orientation of gravity changes how we pedal.

That’s not all that happens when you move forward and lower. The position of the fulcrums (hip, knee, ankle) change in relation to the fixed pedel circle (the bottom bracket). It shifts the portion of the pedel circle when our legs are most efficient, and capable of the most power output, clockwise. You mentioned a study where it was shown that going up a hill does not change muslce recruitment patterns, which is true, so long as the riders position on the bike does not change. If you slide 3-4cm back on the saddle, it does change, just as it changes when you move 3-4 (or 8-9 comparing 5cm in back of to 3-4cm in front of the BB) forward. Now whether this results in any change in sustainable power output is a completely different matter, and probably best answered by you comment about specificity.

Scott

16

That’s not all that happens when you move forward and lower. The position of the fulcrums (hip, knee, ankle) change in relation to the fixed pedel circle (the bottom bracket).

No, in my example (and in the studies I reviewed) these things are held the same. If the point of rotation is the bottom bracket, the “position of the fulcrums” do(es) not change in relation to the bb.

If you move forward and down by way of rotating around the bottom bracket, none of your muscle activation patterns change in a material way. This is the basic premise of the use of a special bike for TT and triathlon. Leave things the same, yet have a lower frontal area.

Other things change, like weight distribution and, hence, bike handling. But, that’s a topic for another thread.

“If you slide 3-4cm back on the saddle, it does change, just as it changes when you move 3-4 (or 8-9 comparing 5cm in back of to 3-4cm in front of the BB) forward. Now whether this results in any change in sustainable power output is a completely different matter, and probably best answered by your comment about specificity.”

Agreed. I think the joint angles that any given athlete decides upon is a choice only they can make (same with cadence). I would just suggest that, once the athlete decides on a set of joint angles (meaning, “bike fit”), then they should stick with it and race and train that way. They should not switch around based on some myth regarding what angles are better for climbing and whatnot.

Two final opinions, though: (1) For non-drafting races, aerodynamics is awfully darned important, so consider your frontal area while deciding on your joint angles and how you want your triangle rotated.

(2) If running off or onto the bike is part of your sport, consider whether the joint angles at which you run are better replicated on the bike with an open or closed thigh-torso angle. Given the principle of specificity, there is something to be said for riding our bikes with as open a thigh-torso angle as we can get. Our optimal joint angles are a product of repetitive training, and the open angles we train while running might be de-trained by cycling with closed angles, and vice-versa.

17

Whoa. STOP! Everyone read Slow Man’s piece on geomoetry and power. I just did. WOW!

18

Whoa. STOP! Everyone read Slow Man’s piece on geomoetry and power. I just did. WOW!

As you might have guessed, I am squarely in the Slowman camp about this stuff.

I’ve tried it lots of ways, and I keep coming back to what Dan’s been saying for nearly 20 years.

20

"Cerveloguy, is this the one you are referring to:? "

Yup. That’s it. Thank’s Craig.