I just wondered if anyone had come across any research about whether crank length impacts muscle patterning, or the muscles used.
Since changing to short cranks I have noticed greater utilisation and subsequent fatigue of my hip flexors, just as an example.
I have attributed this to the fact my hip angle is more open, so I am able to use them more.
I have also noticed I’m not using my quads as much, is this because they have less time to act due to reduced and so length of time in the power phase of the stroke?
I assume your RPM changed? If your RPM did not change, at the same power, you are apply more crank force on shorter cranks. If your RPM increased you may be applying the same or less crank force at the same power.
This will be interesting to watch. I’ve noticed that since switching to shorter cranks on the tri bike I use less quads… if I focus on a good pull, I’ll incorporate some of that group, but nowhere near what I used to and what I do on the roadie. Helps with the run, for sure. (For me anyway)
I think…no…doesn’t the recruitment of FT muscle fibers increase, rather than ST muscle fibers. You are using the same muscles per se, but taxing the metabolic system differently.
let’s say his power generation is X…it will always be X regardless of the lever arm? With shorter crank, without higher RPM, the torque period on the pedal face remains the same. At a higher cadence, it’s a shorter torque period but that torque period happens more frequently.
I think…no…doesn’t the recruitment of FT muscle fibers increase, rather than ST muscle fibers. You are using the same muscles per se, but taxing the metabolic system differently.
let’s say his power generation is X…it will always be X regardless of the lever arm? With shorter crank, without higher RPM, the torque period on the pedal face remains the same. At a higher cadence, it’s a shorter torque period but that torque period happens more frequently.
I did not ask if his power changed. I assumed his power stays identical. I was just asking what happened to his RPM or his crank torque (or both). You can’t keep the same power without at least one of those changing…power = force x distance x 60/RPM. If you chance distance (crank arm length), either force or RPM is changing to keep the same power
I’ve just not had it in my hip flexors like usual, I’ve felt more fatigued. That could also be to do with taking the Q rings off. I always felt these did nothing for cycling but were a real benefit for running off the bike
Power hasn’t changed a lot, it certainly hasn’t changed on the turbo, if anything it’s gone up! And a recent bike split would say it was unlikely to have gone down. (I only use power on the turbo as I have a set of powertap p1s and they are as aero as a barn door!, so speedplay outside)
Thanks. I used to road race on 175, switched to 172.5 for tri, and thinking of trying 165 to help both my position on the bike and my run off the bike.
I’ve just not had it in my hip flexors like usual, I’ve felt more fatigued. That could also be to do with taking the Q rings off. I always felt these did nothing for cycling but were a real benefit for running off the bike
Power hasn’t changed a lot, it certainly hasn’t changed on the turbo, if anything it’s gone up! And a recent bike split would say it was unlikely to have gone down. (I only use power on the turbo as I have a set of powertap p1s and they are as aero as a barn door!, so speedplay outside)
For sure if you are using your hip flexors more your run will suffer, but why don’t you just pound down on the 155 with higher RPM with slightly lower crank force instead to get the same power, rather than using Hip flexors to lift over the top. As an example Brent Sutton gets his athletes to focus on a lower RPM for their longer races to save the hamstrings and hip flexors for the run
For sure if you are using your hip flexors more your run will suffer, but why don’t you just pound down on the 155 with higher RPM with slightly lower crank force instead to get the same power, rather than using Hip flexors to lift over the top. As an example Brent Sutton gets his athletes to focus on a lower RPM for their longer races to save the hamstrings and hip flexors for the run
“spinning circles” is really really bad for running off the bike. You should only use your hip flexors enough so you can pedal smoothly without bouncing. You should be focusing on a strong downward push with some force when going “over the top” as well (leg extension), but NOT Scraping your foot (hamstring) or lifting up actively. I think it helps to ride heel down (might need ot lower your saddle) rather then toe down, too much. At least it helped me. I used to ride very, very toe down, but changed when I went to midfoot cleat position and have some Achilles injuries. I only ride toe down now when out of the saddle climbing on the base bar or in aerobars.
Power hasn’t changed a lot, it certainly hasn’t changed on the turbo, if anything it’s gone up! And a recent bike split would say it was unlikely to have gone down. (I only use power on the turbo as I have a set of powertap p1s and they are as aero as a barn door!, so speedplay outside)
Dude. You bought a pair of $1200 power meter pedals that you only use inside on the trainer because you think they aren’t aerodynamic enough to use outside. That is insane.
The pedals probably do not cost you even 10 grams of drag relative to your speedplays, *if *that, and the advantage of having power in a race is orders of magnitude greater than that.
Not only that, you’re coming on here trying to guess whether your equipment/position changes have garnered greater efficiency, because you don’t know, since you don’t use the most important piece of equipment you own to gauge it.
Why did you even buy the pedals? You should have bought a power meter you considered to be sufficiently aerodynamic, like a Quarq or a Power2Max.
Would you ask, “Does saddle height change muscle use?” ?
Crank length is just another personal parameter in your biomechanical and dynamical chain. The fact that manufacturers have made some quantized lengths more popular, ( eg. 172.5) or that some coaches cling to the notion that there’s a Golden Ratio formula for crank length is just noise.
Consider this: the more aero aggressive you want to be – which is a personal choice – the shorter your crank length probably needs to be.
Yes very true.
But can you go TOO short for your legs?
I have very long legs, about 36 inch inseam. Based on calculations I should be on 180s!
But I have gone to 155, I wonder whether that jump was just too much.
I also seemed to start developing bilateral calf issues when I switched, I use near mid foot cleat positioning so this baffled me somewhat!
OK, I’ll tell you what I watch for. But I’m also making use of a Retul Vantage system.
First, I always consider a rider’s goals.
My own are probably different than most people’s goals on this forum: I want to be comfortable so that I can ride for more than 2 hrs. And I’d prefer to use the 172.5mm Quarq cranks that I own. See – I’m already way off the norm. My back angle is way high and I have no trouble getting over the top of my pedal stroke.
I’m going to assume that your goals are different. That you want to be as fast as possible and you have no equipment sponsorship constraints.
A lower back angle almost always is aerodynamically faster. That’s for most people I’ve worked with, except a few Olympic and pro outliers. I’ll bet you want to be more aero.
There will be a point where lowering your back angle will start to cause your hip angle at the top of the pedal stroke to pinch. This might be manifested in a subtle hip sway, or lowered power, or pain in the hip flexors.
It’s at this point that, if all other things check out ok, I will consider using a shorter crank. And, sure, it is possible to go too short, but it’s also impossible to tell until you’ve put a few kms of riding in them. Shorter cranks will sometimes feel way way better or will feel weird. Everyone’s different.
If you want to stay conservative, I would say that you should use the longest cranks you can that don’t create a pinch at the top of the pedal stroke. That said, most people are on cranks that are way too long.
There is much much more to bike fitting than this, though. I’m just sharing my own implication in contributing aerodynamically efficient solutions to an existing bike fit. I always work with excellent bike fitters, who are there to make sure I don’t do anything stupid.