I like the photos showing the angles. They seem very useful and I’m considering doing the same with my bike fit photos. But I have one question. Where should the pedals be when measuring the hip angle and leg extension angles? In “her” photo the cranks are almost vertical. In “his” photo they are about 10 degrees off.
Thanks,
-Adam
You noticed a problem with the technical validity of this technique of fitting people, of which there are several more:
To directly answer your (very good) question, we look for 150 degrees of leg extension using a goniometer with the foot at the 6 O’clock position of the pedal stroke. I noted that Dan and Fiona at Endurosport mentioned they prefer to measure the joint angle at full extension, which actually (as they pointed out) occurs just slightly before 6 O’clock in the pedal stroke. Full leg extension occurs when the leg is in line with the seat tube at the “apogee” of the pedal stroke. Measured there, I would expect to see an extension greater than 150. Also, we observe and listen to the person’s pedal stroke and also ask them scripted questions about their neurological (feel) feedback of their saddle position. Observing the pedal stroke from the front and rear to look for rocking on the saddle is also a useful tool in determining optimal saddle height. Good observation. thank you for looking so carefully.
Without being able to pinpoint the exact location where the knee joint is, the femur hits the hip etc etc these angles are “ball park”, probably pretty close but as you cant pin point the exact location the scale could distort things a couple of degree’s either way is my guess.
I suspect that as this is being refined rather than relying on angles it would be more on ensuring all points of contact are consistent relative to each other so that if on one person with longer legs and another with a longer torso short legs the same principles can be used to fit the person with vastly different numerical values.
On the other hand maybe the angles are right and thats the way people are fitted…meanwhile back in the bat cave…
the female being positioned might want to pedal with a flat foot when being positioned, instead of toes down, before measuring knee angle
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the female being positioned might want to pedal with a
flat foot when being positioned, instead of toes down,
before measuring knee angle
Shouldn’t she pedal however she pedals? That is, shouldn’t one pedal the same way for a fitting that one does on the road?
I think the point was that you cant compare the 2 angles if they are measured in different ways, if she is in one position with a leg more extended and he is in another with a flat foot discussing the affect that a 10 degree difference in the angle has on the setup or position is clearly pointless as you are not comparing apples and apples.
That combined with the fact that you cant isolate the exact location of the various joints probably makes discussing angles of +/- 5 or more degrees fairly difficult. What you could do is overlay one print out over the other to see how they compare though in terms of relative position.
I understand all that. Gary specifically recommended
“the female being positioned might want to pedal with a flat foot when being positioned, instead of toes down, before measuring knee angle”. My specific question to this specific recommendation is: why? Why should she pedally differently “when being positioned” than when riding normally?
Also, regarding your point: “if she is in one position with a leg more extended and he is in another with a flat foot…” That seems irrelevant. The point is not to compare her position to his position, the point is to compare her before vs. her after (and likewise his before and his after). Despite the innaccuracies you correctly point out that are inherent in the methodology, I find the before and after photos instructive. Her foot looks like it’s in the same position in each of her photos.