i have a Giant Escape City Hybrid. I had th stem swapped out to help with pain in my hands. Previous to that the guy at the lbs moved my seat forward I told him everything else was fine, the only problem was my hands.
I rode the bike 20 miles saturday after I moved the seat back about one inch and my hip flexors are sore, very sore. Is this a symptom of the seat being too far back?
This is a simple drawing of the "KOPS" principle (Knee Over Pedal Spindle); basically, it's a measurement that puts your leg at the proper angles to produce smooth power without excess effort. The drawing calls for that line down from the knee to SPLIT the pedal axle; personally, I like it about 15-20mm behind it. More than that, and I feel like I'm pedaling through deep sand; less, and I feel like half my leg muscles are getting left out.
Some people swear BY 'KOPS'; some people swear AT it. But get checked, so you know if you're close or not, and can GET close.
Also, moving the saddle a full inch all at once can cause that, since it changes how your muscles work in the pedaling motion; too much change=pain.
Sore hip flexors are a sign that those muscles are doing more work than they are accustomed to doing. For example, I snowshoe in winter. During the first outing of the year on snowshoes, hip flexors get a bit sore but are fine thereafter. In your situation, if moving the saddle did relieve pressure on your hands, then that was the correct thin to do but a whole inch (3-4 cm) is a great distance to move a saddle in one go. Try moving the saddle in smaller increments, say 3-4 mm) until a happy medium is reached.