Robert, keep the stretching going and see a specialist (i.e. Physio therapist) to find out if you have some other issues which are creating tightness and/or straining the tendon. Hamstring tightness or other seemingly minor issues may be creating this problem.
Also, if you are over 35 then you are more prone to an achilles tear/rupture, especially if you play hoops or tennis so don't just brush this off. I tore my quad tendon in Nov 09 and have learned a whole lot more than I'd like to have about this stuff. Good luck.
I agree with Kenton. Continue stretching and see a therapist to get this issue resolved quickly. soaking your foot in a bucket of ice water 15 on 15 off is also helpful. Spend some time working on your calf and hamstring by using something like tennis ball...something harder or softer depending on your pain tolerance and see what you can find in there. But again make sure you see a therapist.
I had an inflamed Achilles a couple of years ago. Didn't rupture, but apparently an overuse issue. The 35 or older thing mentioned by Kenton is true. It felt like I had sandpaper in the back of heel, a gritty feeling when I flexed it.
NSAIDs (Aleve for example) and ice help reduce the swelling. Massage and locally heat the tendon, this part of your body has terrible circulation so heeling is slow and this helps. I was getting a deep tissue massage from a therapist. The doc also had me in a boot for a few weeks. That is to immobilize the joint, because once it's inflamed it needs to rest otherwise repeated irritation will keep it inflamed.
To prevent it, you need to stretch and do exercises to increase strength. Leg, lower back & ankle range of motion and flexibility help reduce stress to the Achilles. Getting up and doing heel lifts throughout the day is an easy way to get in a little exercise and stretching.
I got achilles tenonitis from a worn out cleat that kept me off the bike for almost 2 months with several starts and stops.
Here's how I finally beat it:
Rest - After having the pain return after 3 restarts, I took 3 weeks off the bike. During that time, I elevated and iced the tendon every night, stretched, and also made an effort to walk with perfect posture...this helped a lot, believe it or not.
Start back easy: My first rides back were super easy. Short distance, very small gears.
Tape: You can ease the strain on your tendon while riding by taking some cloth tape and running a piece from underneith your heel to the bottom of your calf muscle, going up the center of the back of your leg. Then cross this piece with two or three 'bracing' pieces, that come up to your shin bone on either side. This prevents your heel from dropping, and takes strain off your tendon. This will allow you to ride longer, but resist going too hard, because this in turn increases the strain on your knee...be careful.
Continue to ice and stretch. Be patient, and take everything in small steps. Like you, I had this problem going into July, and was able to get back into 'cross in early September with little problem...a little slow, but able to play and improve with time.
Thanks for posting this Robert and for all the helpful advise from the rest of the CXM folks. I have had the same issue bugging my right achilles tendon as well since last cross season. Keep us updated on your progress and I will do the same. Getting old sucks but it is better than the alternative (I just turned 40 this year)!