There’s a new EPIDEMIC in Pro Cycling!

What do you guys think? Who has an opinion on this?

Shorter cranks, higher saddle, higher stack and riding less. Deal with it.

Well, you may simply switch to a recumbent and will never face this problem at all! And not OTB! And no use of your head as a crash zone. Oh, yeah, UCI has forbidden it nearly a hundred years ago, because it is so unfairly fast and aero, how could I forget?! 😂

Thank you James for bringing this up! My personal take on this matter is quite odd and to an extent flips the medical consensus on its head. I came to think that the meaningful damage happens mostly when fully extending the knee under the condition of hip flexion. Not necessarily massive hip flexion, just enough to anchor the artery around the psoas and cause one to rub against the other — artery moves while the psoas is pressing on it, hard. Knee extension lengthens the path that the arteries of the leg need to take, due to how they go posterior to the knee joint. This pulls the arteries in the leg lower down, causing motion in the iliac artery, which is resting on the psoas. To an extent this is okay, we wouldn't be able to walk otherwise. Under extreme angles though (large hip flexion and large knee extension) the arteries might start running out of their natural length, which means that tensile forces appear that stretch the arteries, including the iliac, lengthwise. Such tension effectively causes the iliac artery to press on the psoas harder, all while it is bent around said psoas fairly tightly. If the knee extension continues, then — unless it's paired with a marked decrease in hip flexion — the iliac artery will experience a combination of lengthwise tension, as well as friction over the psoas while moving around it in a tight bend.

This situation would be at its worst towards the bottom of the pedal stroke, where peak knee extension and fair amount of hip flexion combine. Fit-wise the mechanism I described would be encouraged by longer and lower positions, positions with more anterior pelvic rotation, too long cranks, excessive saddle height, insufficient saddle height, saddles that are too wide in the wrong places and thus discourage hip extension; the list probably goes on further. Excessive and insufficient saddle height listed together isn't paradoxical, merely a juxtaposition reflecting the complexity of the issue as I see it. This mechanism of injury could even take place regardless of fit, if someone has a pedal stroke that's very tight in the hip but extends the knee violently as far as possible. Of course individual predispositions are likely to have an influence as well, regardless of what the mechanism of damage is.

As I have on numerous occasions heard that my writing is, unfortunately, incomprehensible, the redpill of my argument, put together by Chatgpt, is as follows: "The damaging condition [in my opinion] is simultaneous high knee extension and meaningful hip flexion, because that combination produces both longitudinal tension in the leg arteries and local bending + friction of the iliac artery over the psoas."

The way I thought of this is I considered situations on the bike when the sciatic nerve gets stretched and irritated. Why would I bother with the sciatic nerve? Because you have feeling in it, and it runs parallel to the arteries of the leg, only it's not anchored by the psoas but rather by the pelvis. And you might feel it complaining sometimes when cycling. But it's not the same thing, so my model is, as all models before verification, a big guess.

The model I propose, however, gives a causal explanation to how riders tend to list off to the right and the condition tends to occur in the left leg. Also fits with how the pros who get it often have their saddles high, with large peak knee extension — to my eyes at least. Furthermore, those who get it aren't exclusively high-hip-flexion super-aero time trialists, but all kinds of riders, surprisingly often cyclocrossers — and as we know in 'cross positions aren't really aero, but you do need to unweigh your saddle often by lifting your self a bit above it. Finally, there's a lot of strenuous activities involving hip flexion far greater than during cycling, and people do them with no vascular problems, apparently.

I do have absolutely zero formal medical training, so take my theory with a grain of salt. Or two, for all theory isn't worth much without an experiment, and nobody has taken proper laboratory measurements on this yet. I don't even know if it's possible to do so.

For the people who aren't bothered by additional weight on the hands/arms/shoulders, some combination of a forward (possibly raised) saddle position and short cranks. The triathlon folks figured this out a long time ago. Otherwise the comedy answer is that we should all by on recumbent trikes.

Crank length also affects the RPM. So it brings up the question whether the time in the extremes or the times (note the plural) in the extremes have any impact.

It could make some or none difference in either direction.

Video Idea:- From something you said in the video about the balance between "doing right" and "making a quick buck or two", Perhabe you should make a video about the bike fit industry, who to trust and how to find them (since we can't all go to you). How many people go to fitters anyway?

12:00 Is the reason that your clients are mainly middle aged desk jockeys because they watch professional bike riders and buy a bike based how they look, e.g. arse up & head down?

Good discussion James. Well done. I heard this talked about at a Youth coaching session where there was a warning about setting your bike up for fashion, hand me down bikes, one of the reasons they used rollers and cadence drills in young riders. I wish I had taken more notes now.

Super interesting subject.

This is super interesting. We need some medical experts and maybe some fMRI scans at different degrees of hip flexion.