@lisboneu This study is dumb, because it starts with a Q1 of 151 (most road bike cranks are 143-148 these days, quality MTB triple cranks are around 175, and cheaper ones may be 180-190, fat bikes are 205 or a little more. So between Q1 and Q2 are the vast majority of real bikes. Training bikes are another story.
Most people are really close to 150 or 155 and younger peoples joins are more flexible and develop and adopt to a Q-f. Older people have a harder time if they didn't cycle all their life. Some peoples' lower legs bow out a bit and trying to ride with 150 hurts. I can't even do half the distance I usually do without hurting, and it took me a while to figure out why on a mediocre hybrid weigh 2-3kg more than my road bike I could climb and do longer distances "easier".
I did some research on this too. I tested some friends and some people I don't know too well that hang outside a b.shop on Saturdays. Put your hands on some solid rail about as high as your waste, stand at a distance to simulate riding. Without looking down raise one foot up to about as high it gets on pedals (like 1/4 distance down from foot-knee or 340-350mm 14") lower bring the other, like jogging slow but stationary, say 50-60rpm. Then stop, while still balanced, without movement left right. Have someone measure from the inside of your shoe at pedal axis area (fattest area of foot) to the other. Do this about 10 times and take an average. Subtract a small amount you think is reasonable or is the actual distance from your clipless shoes to the outside of the crank (x2 for both sides). That is your natural and comfort Q-f. Your "stance" shouldn't be different when cycling or running. If it is then after a while you will not be able to run. Does anyone out there do hours of training on a bike and then can't walk too far?
If you are close to 150 with an average road bike crank you are doing fine. If you are measuring 170 and more you may benefit from a different crank, or pedal-spindle extensions, or pedals with longer spindles from factory. If you are measuring 180 or more, I will be surprised if you are riding a road bike at all and didn't give long ago.
Cheapest option is to get MTB cranks made for a 73mm BB, and are usually wider in Q-f, but not all, check the specs of the specific model. There are some Durace MTB triples that are slightly over 150. The old cranks with square tapered cartridge type BBs you can get in wider sizes. The modern 2 piece cranks there is nothing you can do to affect Q-factor.
PS Hip size is not actually an accurate indicator of Q-factor. Your legs may start wide at your hips, go straight down your knees, and then bow in, and vice versa. So a "wide" structure may need a slim Q-f and a skinny skeleton may need a huge Q-f. On pavement your legs are not restricted to where they step, unless you are trying to run on top of a stripe. So your feet fall in the distance your structure feels naturally more stable and comfortable to run.
PS2 Have you noticed with cleats that float your feet swingin from one end of the float angle to the other extreme while going up and down? That is a clear indication the Q-f is restrictive and your knees are twisting and turning trying to do work with your feet strapped too close or too wide. MTB riders may have the reverse problem ... so they take up CX
