Trochanter at the BB center (90 degree seat angle) is not a good setup. Almost every bike will be too short and you will, as you say, be very quad dominant (increased external moment arm to the knee joint).

5-10 cm behind the saddle is a good range. Find the most comfortable one, where the top hip angle is open enough to be comfortable and powerful but not so open that you sit right over the BB.

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Endurance coach | Physiotherapist (primary care) | Bikefitter | Swede

Thank you very much for the reply

This issue is not going to cause the same sort of argument as say, disc brakes vs. rim brakes, but I will certainly throw out my experience. My seat nose is at 5cm in front of the bottom bracket and I ride on the end of the saddle. That probably puts me at the 90 degrees you are talking about in your post. That is the only way I can relieve the strain in my butt muscles and feel comfortable. I don't notice that it employs the muscles any differently. Certainly, after a time away from the tri bike, when I transitioned back I did not really notice anything more sore than usual. Of course, I push all my saddles and seat positions as far forward as they can go on any bike that I ride.

Thank you very much for sharing your experience.
Maybe it's adaptation.
Thank you very much