After some achilles tendon pain coming off a big week of training, I decided to re-examine my fit. Using wrenchscience.com and Peter White's online guide to fitting, I gave myself a fit that involved lowering the seatpost about 2 cm and slamming the saddle all the way back.

Good lord, the bike is 10x more comfortable than it was. Lowering the seat post took care of the achilles tendon pain and my pedal stroke feels so much more fluid now, and slamming the saddle all the way back has taken the pain out of my neck and shoulders and changed the feel of the saddle from "rail like" to something like sitting on a stool.

The only issue is this.. my hamstrings! They are wicked sore after just a short ride 1.5 hours. I'm much more bent over now, but much more comfortable as well. And I'm not talking about pain, but definitely sore, as if I'm activating new muscles that haven't been used before.

Is this a good thing? Is this just the adjustment phase? Would it be better to slide the saddle forward a bit to share more load with the quads?

Try a longer stem eventually and moving the saddle forward some. I used to have my saddle slammed back but it was because my stem was too short.

For me, I find lower bars and/or riding in the drops increases engagement of the hamstrings and glutes, which IMO is a good thing. It certainly stretches your hamstrings and glutes. It may be you're experiencing something similar if you've only been riding in a more upright position.

Yoga.

Since I doubt you'll do that, I would do mild stretching when cold, which is all you can really benefit from.. but then the key is significant stretching when you finish or stop for more than a traffic light. You need to warm stretch for minutes, not seconds.

I would consider that a good thing. Sounds like you're engaging your hamstrings more now. That happened to me when I transitioned from a commuter to a road bike. My speed also increased noticeably after a few weeks.

It's likely an adjustment thing but you made too much of an adjustment all at once. Most of the advice I read is only make seatpost adjustments in 1 cm increments until you get used to it and the same with saddle position.

+++1 !

if you're set on getting to the 'new' position, I would make the change in increments, 1 cm for height is a bunch, and certainly for fore/aft 5 mm is a lot.

I'd go back and make the changes in 1/4rs or 1/3ds over a period of 5-6 rides per change. Give the body a chance to adapt without overdue strain.
Means way less chance of causing both muscle and connective tissue injury... which might take months to heal.
changes you make in seat will have large reprocussions all the way up and out thru the body
hamstrings, especially can cause naggin injuries for very long periods of time.
or
you can take your chances...

Well, the nice thing is that I have no more shoulder or neck pain, and when I have someone hold the bike for me while I take my hands off the bars, I don't tip forward and the saddle still feels like it should be right where it is (in its new position). Maybe the key is less mileage while I adjust, rather than incremental adjustments. I'll decide on that later.


Question: What has the potential for more power, glutes/hamstrings or quads? is it a good thing to use hamstrings more? Or should I possibly sacrifice comfort, engage more quads, (and get more power?), by sliding the saddle forward?

there's a few recent threads regarding your question. quads are at least 50% of your power, more if you have an abbreviated stroke (like a piston) and less if you are more efficient through the revolution. glutes and hips are another 20-30% depending on your posture.

hamstrings do very little. calves don't get much work either unless climbing, but more than hamstrings.

your hamstrings probably hurt due to stretching them with your new body position. thus, my first reply about yoga and stretching.

I'm all about the yoga, just can't find time to fit it in

fail

https://www.ncbi.nlm.nih.gov/pubmed/3732250
only 1 of many with similar findings...

from the abstract:
"...The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%."

all of this is, of course, affected by position and pedal style, you can't heavily favor any one area without the whole process failing...

that why most cyclists have such wonderful lookin legs, except for the scars... unless you dig scars

I wouldn't consider it an over-adjustment if joint or back pain goes away and all you get in the negative is muscle soreness. As long as its just soreness, that's just a muscle being activated in a way that it wasn't before. Now, if that soreness includes any kind of connective tissue or joint pain, that's when I would back off.