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Back shape
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zebragonzo
Nov 2, 09 8:03
Post #1 of 8 (229 views)
Back shape
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I've just been looking at some photos from my club's track championships and noticed a distinctly different back shape between riders.
Are these the different back shapes between riders 1 and 2 the ones that are often referred to?
Anyhow, is either one better than the other?
jyeager
Nov 2, 09 8:43
Post #2 of 8 (196 views)
Re: Back shape [zebragonzo]
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yes, those are the 2 shapes.
Rider 1 won't have so much pain in the taint, but will likely develop back trouble in time.
Rider 2 won't develop the back trouble but will complain when he tries to do longer rides in this position.
I'm not sure that one is known to be better than the other in all situations. Each one will have a different optimal arm position and helmet choice.
Actually, as I look more closely, at least in this particular example, I can be fairly certain rider #1 is LESS aero than rider #2. It looks like rider #2 has a higher seat as well as a lower chest.
Rider #1 will be catching more air under his chest.
But both riders could be given the same torso height and then I can't say which one would be more aero.
bermudabill
Nov 2, 09 8:45
Post #3 of 8 (194 views)
Re: Back shape [zebragonzo]
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careful, you are letting the genie out of the bottle. people will learn that tri bike fitting is not about hip angles as much as it is about back shape. what sense does it make to fit a bike based on the angle of the bb/hip/clavicle when you have about 33 vertebae in there. careful, you know what happened to prometheus.
zebragonzo
Nov 2, 09 9:09
Post #4 of 8 (166 views)
Re: Back shape [jyeager]
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Thanks for the info guys. Just one small thing:
In Reply To:
Rider 2 won't develop the back trouble but will complain when he tries to do longer rides in this position.
Actually, rider 2 has done a 12 hour TT in a similar position!
jyeager
Nov 2, 09 9:21
Post #5 of 8 (148 views)
Re: Back shape [zebragonzo]
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12 hours? Then that is quite a testament to adaptability or at least saddle choice!!!
zebragonzo
Nov 2, 09 9:23
Post #6 of 8 (144 views)
Re: Back shape [jyeager]
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Lots of back stretches!
jyeager
Nov 2, 09 9:24
Post #7 of 8 (144 views)
Re: Back shape [bermudabill]
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In reply to
]
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In Reply To:
careful, you are letting the genie out of the bottle. people will learn that tri bike fitting is not about hip angles as much as it is about back shape. what sense does it make to fit a bike based on the angle of the bb/hip/clavicle when you have about 33 vertebae in there. careful, you know what happened to prometheus.
Good point. Perhaps we can add a caveat to the whole hip angle paradigm. The actual angle of the pelvis is what we are after, but measuring from the greater trocanter to the shoulder is what is approximating the pelvic angle. If we could accurately measure the leg angle (up through the trocanter) against the trocanter to pelvic bone angle it might be more appropriate.
bermudabill
Nov 2, 09 10:12
Post #8 of 8 (108 views)
Re: Back shape [jyeager]
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In reply to
]
Can't Post
In Reply To:
In Reply To:
careful, you are letting the genie out of the bottle. people will learn that tri bike fitting is not about hip angles as much as it is about back shape. what sense does it make to fit a bike based on the angle of the bb/hip/clavicle when you have about 33 vertebae in there. careful, you know what happened to prometheus.
Good point. Perhaps we can add a caveat to the whole hip angle paradigm. The actual angle of the pelvis is what we are after, but measuring from the greater trocanter to the shoulder is what is approximating the pelvic angle. If we could accurately measure the leg angle (up through the trocanter) against the trocanter to pelvic bone angle it might be more appropriate.
I think you are on to something there. measuring the angle of the femur (at the trochanter) to the pelvis is difficult though. where on the pelvis do you measure? Illiac crest? Plus, pelvic bones vary a lot. if you could measure the femur in relation to the sacrum that might be useful. it would be interesting to put a small strait edge on the sacrum and a mark a line of the Trochanter to the lateral epicondyle and see what that shows.
But the key is looking at lumbar curve primarily then the thoracic. the thoracic area can not bend forward much, about 1* per. otherwise you would disslocate/break ribs. although some people have the characteristic hump - kyphosis(lance?). plus you are going against the natural curve.
there is a lot of flex in the lumbar region, especially t12/l1. also, you want to consider that some of the hip flexors attach to the lumbar spine - so does this open the hip angle better than moving the seat forward? does a more vertical sacrum allow for more power, especially for those with tight hamstrings. A lot of people feel that flexibility is not important to cycling because the ranges of motion are not extreme but maybe for TTs they are?
compare your rider #1 to Matt Reed here
http://forum.slowtwitch.com/...t_reply;so=ASC;mh=25
;
good stuff, let's see what comes up.
(This post was
edited
by bermudabill on Nov 2, 09 11:11)
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