Inspired by the <.21 CdA thread going on, I have seen pictures of people reaching very low CdA with both parallel arms as well arms angled up. I know it is very individual and really needs to be wind tunnel or road tested, but I’d like to collect some experiences from those poeple who have tested the postion.
I’d like to hear your increase/decrease in drag, and also your height, inseam, and shoe size.
Shoe size?! Yes, based on the rule of thumb that shoe size correlates to the length of your forearms (forearm being the main change that gets angled up during the praying mantis postion).
My theory is that shorter riders, with shorter arms, will benefit more from the arms up postion since there is less area to close off between elbows and face. Taller riders will usually have longer arms and will have more arm for the wind to hit.
Yes there will be tons of exceptions, but I’d still like to hear experiences and try to create some rule of thumb. Thanks in advance for your experiences and the arguments that will soon ensue.
Timely post. I am looking at buying a pair of ski tip extensions for my bike to get closer to this position. Currently I have straight bars and I hat them, I do not like that bend in my wrist.
Well 1 rule but it’s a limited sample size. hands below the elbows have always tested slower vs flat or angled up hand position when I’ve tested it. But it’s a small sample size so would need more testers to prove or null it.
I can disprove your arms up theory. I can prove your arms up theory. You should write better theory’s
i’ll simply give you an n=1, 7-8w hit for lower hands vs higher, and I am not talking mantis higher either, merely tips of extensions 8-10cm above pads
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My N=1 as well, Mantis was worth about 20 grams over my second best position, which was low slightly stretched and elbows tight (almost touching). 2-3 watts or so.
The issue on the open roads with traffic etc was I felt a bit tippy or unstable, I tried it for about a week and then went back to second best position. There are also a bunch of variations of Mantis that you might want to test…high vs low, elbow width etc.
My comments below are based on years of doing fits, speaking with fitters and with physical therapists…
Broader shouldered individuals tend to fair better with hands higher than elbows, how high depends on a few factors.
Broader individuals tend to need to adduct the arm relative to the shoulder to gain an acceptably narrow forearm position, if their hands remain level or even lower than elbow the tendency is to “lock up / clamp down” that front end in pursuit of stability. These two things result in isometrically loading the biceps, the biceps inserts onto the scapula, thus “locking the scapula” in place and… the net result is you know that “turtling” of the head down that many seek to gain lower CdA?..now you can’t do it as that upper back area is all locked up and so now you end up with that “goose neck” position impacting on comfort and what is most appropriate helmet.
So the short answer is (relative to arm length)…broad shouldered?..raise hands to allow head to comfortably drop down & forward…narrow shouldered?..you can probably gain lower CdA with flatter and narrow forearm position.
And if anyone thinks this is tosh here’s easy proof…place elbows, forearms, wrists, fists together with thumbs facing your face and elbows just below chest height. Now slid forearms in upward direction until elbows are now mid chest, feel upper back tighten?..Now tip wrists away from face, feel upper back tighten more?.. Now try dropping your head down and forwards toward wrists, highly unlikely you can.
Huh, that explains something that I’ve experienced on my own in experimenting: slightly wider elbows vs my narrowest achievable position (nearly touching for me with upper arms ~85 degrees) puts a lot less strain on my neck and I never understood why.
This seems to line up with what I saw when I played with mantis positioning, when I looked at pictures with and without mantis my head position looked better and I noticed that turtling was easier and more natural. I could still turtle in a non-mantis position, but it took much more attention and effort.
