Saddle height and muscle re-training...
 

No question here, just my recent experimenting:

I had been thinking my saddle was too high due to feeling stretched at the bottom of the stroke, and that seeming to cause a sore bottom.

So I lowered it about 6-7mm, and on my first 2 hour fast group ride (fast enough that the 4 person "A" group left me behind half-way through the ride after my pull and I sat up and got caught a few minutes later by the "B" group)...I was really feeling like my hamstrings were working harder than normal, almost about to cramp, but they never did. However, When I stood to climb or sprint, my quads felt really good, like they hadn't been working as hard.

2 days later I did a sprint interval session on the trainer and noticed the same sensation sitting and standing. Research online confirms that lower saddles work the hamstrings more.

In My interval session especially, I found I was enjoying alternating between standing and sitting, and noticed that overall, the session seemed to take less out of me than normal, since every other interval was focussing on different muscles.

Perhaps a tiny bit higher saddle is the ideal position, but my plan is to leave it alone for a few weeks and see if my muscles get used to the different recruitment.

Thanks for reading,
Any thoughts welcome!

Did you check your knee angle at full extension? Easy enough to do on the trainer with the phone. Bike Fast Fit does the work for you

I find the same thing. Too high a saddle position takes the power out of my hams, so that's how I fine-tune my saddle height. When my hams start to go, I push forward at the top more and pull back less at the bottom, and vice versa with my quads.

The quads have the advantage of a kneecap up there to help with leverage during leg extension. On the backstroke, ham power is going to depend on the point of insertion of the hamstring tendon at the knee, which varies with the individual. I think a little more bend at the knee is helpful for those with a close insertion than for those with a wider insertion.

Champion weightlifters commonly have tendon insertions a little further from the joint than most of us.

Thanks for the input. What started the whole thing was that I took a 20 mile ride on an old vintage bike I had restored, one that has shorter cranks (165mm, I measured)...and I really like that aspect of it. So I decided to experiment with my main bike (172.5mm cranks) to see if I could keep from stretching at the bottom of the pedal stroke.

The hamstring effect was unexpected, but I think it might work out if I can strengthen up my hamstrings for the extra load.

I believe moving saddle rearward also puts more emphasis on the hams/glutes. If so, how about lowering your saddle a little less, but moving it rearward a bit? You'll get back some or all of the bb-to-saddle length you lost, but still be drawing more from your hams/glutes when seated.

Interesting! I've always been aware that my lats/biceps/calf/ham muscles were relatively short (i.e. long gap) and attach high up (I'm very long-limbed and figured my tendons stopped growing before my muscles, but have no idea). I assume this puts more strain on the tendons. While weight lifting (supinated chinups and curls), I strained each of my biceps at different times (took years to recover, and right bicep still isn't 100%) and figured it was partially because they attached far from the elbow. Until your post, I had never even THOUGHT about tendon insertion point.

I recently moved the saddle back about 4mm and up 2mm. I'm feeling more hamstring engagement and I seem to be slighty faster and slightly less wiped out on rides. This could all be imagination. The one thing that is certain is to constantly test bike fit because out bodies are constantly changing also.

Assuming you started with a good setup from the get go, when moving the saddle aft, you'd want to also move it slightly *down* -- think of it as rotating the saddle around the crank's axis. You're either going towards that 12:00 position (in a counter-clockwise fashion) - or you're going away from the 12:00 position (in a clockwise fashion).

Think about being directly above the crank axis - your pedal stroke largely mimics a one-legged squat (quad dominant). Now think about being behind and lower on that clock-face - it's almost a forced push - and you can almost feel (just thinking about it as you sit there) the extra hamstring and glute activation required to force those pedals through their stroke.

I consider my *standard* position fairly closer to that 12:00 position than most people - but I can still get sore glutes after a decent trainer session. Of course I tend to utilize the entirety of the usable portion of my saddle too. I wouldn't say it's uncommon for me to spend a good bit of time back near the wings, or slid forward when doing a prolonged climb. I also tend to stand for uphill portions of rollers, etc.

random thoughts on effective seat tube angle
 

If you're seated, then it's more like a one-legged leg press than a one-legged squat, yes? Largely relieved of the task to stabilize, the hams/glutes can more dedicate themselves to producing power. Lift your butt slightly off the saddle and you quickly fatigue.

A quad or ham/glute dominant position? Ideal would be in between, right? Spread the load? Just like you'd mix front squats with low-bar back squats for balanced muscle development?

Many long-femured riders get along better with a slack angle (but then must figure out a way to sufficiently weight the front wheel).

The studies I've seen show a slacker angle produces as much or more power than steep angles. But...those studies are done on a stationary [horizontal] bike. I do find steeper helps when climbing, especially if riding a mountain bike on trails. Sliding forward helps a little.

Update, one month later:

I'm really liking this new position. My butt hurts less, my hams are worked more, and the dramatically different muscles worked between sitting and standing means that I can get out of the saddle at any time and feel fresh as if my quads have hardly been working. This came in handy at my first cyclocross race, when I had to push up short steep hills, I felt good doing it out of the saddle. And on our group rides, going in and out of the saddle made climbs much easier. (In the past, with my old saddle position, standing up was hard as soon as I stood, cuz my quads were already tired from seated climbing.)

Regarding muscle retraining, my hamstrings are gaining the ability to compensate and adapt for the new work load, so I'm happy with that also. A real coach/fitter might say I'm working them too much when seated but it seems to be working for me.

~ Once you learn to ride a bike, you never forget ~

I've utilized that secret dynamic for 10 years on my single speed mountain bike: slack seat tube angle (good torque from posterior chain for seated pedaling on flattish parts) and quads (+ gravity) for standing climbs. I actually have...2 gears.