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New study on the effects of seat tube angle (for those of you who care about this stuff)

 

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jacksonk

Mar 19, 08 18:00

Post #1 of 42 (1775 views)
New study on the effects of seat tube angle (for those of you who care about this stuff) Quote | Reply

We completed this study a couple of years ago but finally got around to publishing it. The original idea for the study design was sparked by some of the discussions on this forum (thanks for your help) so I thought some of you might be interested. Nothing earth shattering and the study certainly has its limitations but it adds to the body of knowledge. BTW, don't critique the pictures too harshly, they were taken rather quickly and don't accurately represent the more precise positioning of the subjects.

The study is published here: http://www.asep.org/journals/JEPonline and is available full-text online. Just open the link to the current issue (Feb 2008) and go to the second page of the table of contents to download the article. The abstract is below for those who just want the cliff notes.

Effects of Seat-Tube Angle on the Metabolic Cost of the Cycle-Run Transition in Triathletes. JEPonline 2008; 11(1):45-52. The purpose of this study was to investigate the effects of two different (73° and 81°) seat-tube angles (STA) on cardiorespiratory measures during cycling and a subsequent treadmill run. Ten male triathletes completed a 40-minute “time-trial” at a pre-determined workload on a cycle ergometer at 73° and 81° STAs and immediately transitioned to running on a treadmill at a pre-determined pace. Oxygen consumption (VO2) and heart rate (HR) data were collected during the last 5-minutes of cycling and first 5-minutes of running. Consistent hip and knee angles were maintained between cycling conditions. There were no differences in VO2 for cycling or running between the 73° and 81° STA conditions. Heart rate was significantly lower during cycling at the 73° STA (p<0.05). There were no differences in running heart rates. These results suggest that if bicycle seat-tube angle is changed, but hip and knee angles remain consistent, there is no difference in the metabolic cost of cycling or a subsequent treadmill run.

Kurt


Rahzel

Mar 19, 08 19:10

Post #2 of 42 (1722 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

Very eeeeeenteresting. The only constructive criticism that I have, which is addressed to a certain extent in the "limitations" section of the paper, is that the cyclists were only measured for the last 5 minutes of the bike portion of the test. Additionally, I hypothesize that an increased STA may have more effect on cycling and running performance if the cycling portion of the test is more extensive. Say, 90 minutes or two hours instead of just 40 minutes.

Otherwise, looks like an interesting and academically rigorous examination of triathlon STA!


msuguy512

Mar 19, 08 19:13

Post #3 of 42 (1712 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

did the subjects mention a difference in perceived effort for the run?


cerveloguy

Mar 19, 08 19:21

Post #4 of 42 (1697 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

"Heart rate was significantly lower during cycling at the 73° STA "

Any explanation for this?


Slowman

Mar 19, 08 19:36

Post #5 of 42 (1671 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [cerveloguy] [In reply to] Quote | Reply

"Any explanation for this?"

i would ask whether cadence was kept constant. basically, all things equal, if you want your HR lowered, lower your cadence. typically, shallower seat angles couple with lower cadences.


Dan Empfield
aka Slowman


roady

Mar 19, 08 19:42

Post #6 of 42 (1661 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [Slowman] [In reply to] Quote | Reply

In Reply To:
"Any explanation for this?"

i would ask whether cadence was kept constant. basically, all things equal, if you want your HR lowered, lower your cadence. typically, shallower seat angles couple with lower cadences.
I was counting the seconds before you caught this one...

Come on now folks--he provided a link to the entire article. There's a hypothesis as to why HR was higher, and the cadence info is all in there.


msuguy512

Mar 19, 08 19:43

Post #7 of 42 (1658 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

I am just thinking out loud, but after the bike ride do you think it would be a better test if you let the subjects run at their own pace. Instead of testing their VO2 or heart rate, test their mile TT.


Rahzel

Mar 19, 08 19:46

Post #8 of 42 (1651 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [Slowman] [In reply to] Quote | Reply

In Reply To:
"Any explanation for this?"

i would ask whether cadence was kept constant. basically, all things equal, if you want your HR lowered, lower your cadence. typically, shallower seat angles couple with lower cadences.
Dan,

I believe that the article mentions that while cadence was not forced to be constant, the participants had approximately the same cadence at 73 degrees and at 81 degrees. 92.x (73) versus 91.x (81) I think. Though I admit that forced identical cadences would be nicer, this seems like a pretty good way to address this issue.


tridork

Mar 19, 08 19:48

Post #9 of 42 (1649 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

1) I didn't read the article, just the cliff notes

2) One would expect the power to be the same if the hip angle remains the same

3) One would expect higher HR when the upper torso is in the aero position, since being in that position is more restrive for the torso (neck extended up, and arm tucked in to at least some extent

4) Even tho the power output was the same for both angles, the SPEED in the aero position would be higher due to lower drag (that's the whole point of aerobars in the first place!).

5) Therefore the aerobar rider (81deg) would get to T2 sooner than the roadie, and run the same speed off the bike

6) A better test would have been to test both riders in the same aero position, but with different hip angles. This would change the power output (one would expect lower power with 73deg, due to being bunched up) and likely the oxygen uptake (and HR for the same power) and the aero effects would be largely nullified. (Important since this is a static (no wind resistance) test)

Just my 2 cents

TriDork

"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"


roady

Mar 19, 08 20:12

Post #10 of 42 (1625 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [tridork] [In reply to] Quote | Reply

In Reply To:
1) I didn't read the article, just the cliff notes

2) One would expect the power to be the same if the hip angle remains the same

3) One would expect higher HR when the upper torso is in the aero position, since being in that position is more restrive for the torso (neck extended up, and arm tucked in to at least some extent

4) Even tho the power output was the same for both angles, the SPEED in the aero position would be higher due to lower drag (that's the whole point of aerobars in the first place!).

5) Therefore the aerobar rider (81deg) would get to T2 sooner than the roadie, and run the same speed off the bike

6) A better test would have been to test both riders in the same aero position, but with different hip angles. This would change the power output (one would expect lower power with 73deg, due to being bunched up) and likely the oxygen uptake (and HR for the same power) and the aero effects would be largely nullified. (Important since this is a static (no wind resistance) test)

Just my 2 cents
I haven't seen any evidence of number 4, and I question (as have others) just how far forward one really has to go to 'preserve the hip angle' when going from a 'slack' ST angle to a 'steep' ST angle.


tridork

Mar 19, 08 21:02

Post #11 of 42 (1584 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [roady] [In reply to] Quote | Reply

In Reply To:
In Reply To:
1) I didn't read the article, just the cliff notes

2) One would expect the power to be the same if the hip angle remains the same

3) One would expect higher HR when the upper torso is in the aero position, since being in that position is more restrive for the torso (neck extended up, and arm tucked in to at least some extent

4) Even tho the power output was the same for both angles, the SPEED in the aero position would be higher due to lower drag (that's the whole point of aerobars in the first place!).

5) Therefore the aerobar rider (81deg) would get to T2 sooner than the roadie, and run the same speed off the bike

6) A better test would have been to test both riders in the same aero position, but with different hip angles. This would change the power output (one would expect lower power with 73deg, due to being bunched up) and likely the oxygen uptake (and HR for the same power) and the aero effects would be largely nullified. (Important since this is a static (no wind resistance) test)

Just my 2 cents
I haven't seen any evidence of number 4, and I question (as have others) just how far forward one really has to go to 'preserve the hip angle' when going from a 'slack' ST angle to a 'steep' ST angle.

TriDork

"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"


slidecontrol

Mar 19, 08 23:47

Post #12 of 42 (1512 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [tridork] [In reply to] Quote | Reply

i had similar thoughts re; 4/5/6.

my understanding is that a steep ST angle allows the rider to get aero while retaining an open hip angle.

by doing the test on an ergometer nullifies the aero effect making the test somewhat inaccurate.


I reject your reality and substitute my own!
Adam Savage


Camel's Toe

Mar 20, 08 9:56

Post #13 of 42 (1325 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [slidecontrol] [In reply to] Quote | Reply

Quote:
by doing the test on an ergometer nullifies the aero effect making the test somewhat inaccurate.
Quote:


I agree that it nullifies any potential aero effect, but I don't think it makes the test inaccurate. instead, I think it may help to isolate the possible list of benefits from riding steep. For example, if this test shows that, but for STA, all other things are equal, then you could presume that the ONLY difference is the aerodynamic benefit, if any, from position. Those who ride high in front could rethink whether they should be on a road bike or tri bike, if not riding aerodynamically (esp. if they find a road bike more comfortable over any given distance). And I suppose you could conclude that the various theories relating to different muscle recruitment (and how they relate to efficiency) are shown here to be disproven, or questioned.

But I don't know that the ergo makes it inaccurate. I'm really suprised this hasn't generated more discussion from people a lot smarter than me - but this place is starting to evolve (devolve?) to discussions surrounding contemplating one dude's navel in the pool area


monty

Mar 20, 08 11:27

Post #14 of 42 (1251 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

I had the same questions about a stationary bike vs real world aerodynamics, but of course they cannot be answered with this study, so it is a moot point here. It does however make all the difference in the world. Only other problem is that who here only rides 40 minutes, then runs 5 or 10 minutes. Just like with wetsuits, the major differences are in the back half of the race, not the first half where you are fresh, and there is not enough time for differences to show up. I bet if you did this test with a one speed cruiser bike, the run results would also be the same, or maybe a unicycle..

The proper way is to do it at race pace for a period of time that gives a chance for any difference to surface, if in fact there is one. You also have to take into account the fitness of the athletes, and what position they have been training in prior to the test. That is the problem with most of these things, there are so many variables, that you really have to do your homework in advance to get meaningfull results....


cerveloguy

Mar 20, 08 11:46

Post #15 of 42 (1223 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [tridork] [In reply to] Quote | Reply

"One would expect higher HR when the upper torso is in the aero position, since being in that position is more restrive for the torso (neck extended up, and arm tucked in to at least some extent "

That is a more logical explanation to me than Slowman's cadence theory since I've always rode consistantly at the same 95-105 cadence on both my road and tri bikes. My HR was always a bit higher on the tri bike on the road or trainer. I always contributed it to two factors 1) holding my neck in more extension 2) crotch discomfort on the tri bike.


jacknine

Mar 20, 08 11:55

Post #16 of 42 (1210 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [jacksonk] [In reply to] Quote | Reply

Very interesting, will keep in mind next time I am on a stationary bike.


rubberband

Mar 20, 08 12:50

Post #17 of 42 (1161 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [monty] [In reply to] Quote | Reply

"...the major differences are in the back half of the race, not the first half where you are fresh, and there is not enough time for differences to show up."

The evidence disagrees with your assertion. Their paper cites two other papers that show that the differences are most evident in the first few minutes of the run, not the second half. Here's a link to one of them.



slidecontrol

Mar 20, 08 12:58

Post #18 of 42 (1155 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [cerveloguy] [In reply to] Quote | Reply

i was thinking about the HR differences between the positions in the experiment.

we know the hip angle was retained between the the two ST angles tested.

it has been 'assumed' the power output was similar although no mention was made in the OP

my next thought was how was the riders front end supported during the test?

we now know ( thanks to the work of Dan and others) the when riding steep the upper body needs to be supported properly (skeletally) on the aerobars rather than muscularly (sp?) where as riding slack moves more of the riders weight over the saddle.

if the front end was not dialed to suit the rider in the aero position, would there not be a measurable increase in HR as the upper body would be working considerably harder to maintain position?


I reject your reality and substitute my own!
Adam Savage


rubberband

Mar 20, 08 13:02

Post #19 of 42 (1142 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [slidecontrol] [In reply to] Quote | Reply

Sheesh, read the article, folks. You can see for yourself whether the rider is supported muscularly or skeletally by looking at the photo of one of the subjects in it.


monty

Mar 20, 08 13:05

Post #20 of 42 (1136 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [rubberband] [In reply to] Quote | Reply

It's quite possible that differences occur at the beginning of the run, but what I'm saying is that you have to do the entire bike first, and then the entire run to ascertain that there is in fact a difference. I'm not sure what studies were cited, but in order to know if you are improving the first part of a run, don't you have to do the second part too?? In other words, if you only test 5 or 10 minutes, even if it is faster, don't you have to test the last 30 or 40 minutes to see if you gave it back for some reason???? Like I said, it is a lot more complicated that it appears at first glance, and I just don't think you get anything meaningful from a 40 minute ride(at some unknown pace), going into a 5 to 10 minute run(also at some unknown pace)....


(This post was edited by monty on Mar 20, 08 13:09)


rubberband

Mar 20, 08 13:09

Post #21 of 42 (1123 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [monty] [In reply to] Quote | Reply

The cite prior articles that studied heart rate, blood lactate, and others (stride rate and length, for instance) for a 10k run a certain rate, versus a 10k run at the same pace immediately following a 40k TT. As I said, those studies showed that the differences were evident in the first few minutes of the run, not in the second half.

I provided a link to one of those studies in my earlier reply.

This fact--that the difference is most evident in the first few minutes of the run--is why they chose to measure only a few minutes of running. Their study may have weaknesses, but I don't think there's good evidence that this is one of them.


monty

Mar 20, 08 13:14

Post #22 of 42 (1111 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [rubberband] [In reply to] Quote | Reply

That's my point, they did a 40k bike in that study, so it may be the beginning of the run, but it is late in the overall race. Sorry I didn't read the study, but did it also show that 73 was the same as 81 degrees? I remember one that showed that steep was better, as well a a higher cadence... Which is opposite from the study of the OP.....


cerveloguy

Mar 20, 08 13:16

Post #23 of 42 (1105 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [monty] [In reply to] Quote | Reply

"Which is opposite from the study of the OP..... "

What does this tell us of the relevance of studies.


rubberband

Mar 20, 08 13:18

Post #24 of 42 (1101 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [monty] [In reply to] Quote | Reply

No, the study with the 40k TT/10k run was focused on the metabolic effects of cycling first, not on STA.

Some of the studies that showed that "steeper is better" changed only the STA, without changing hip angle, and we seem to agree that that's pretty flawed. This article fixes that, at least, but didn't replicate those earlier studies' results.


roady

Mar 20, 08 13:18

Post #25 of 42 (1100 views)
Re: New study on the effects of seat tube angle (for those of you who care about this stuff) [cerveloguy] [In reply to] Quote | Reply

In Reply To:
"Which is opposite from the study of the OP..... "

What does this tell us of the relevance of studies.
I think it goes directly to the point that when reviewing studies, it helps to do more than just read the abstracts....

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