I first experienced Achilles tendonitis at the very beginning of 2014, after running a double race on a Saturday morning consisting of a 1 mile run followed by a 5K about half an hour later. I spent the weekend limping because both ankles felt very sore. On Sunday evening, I discovered that massaging the Achilles tendon area increased the short-term pain but provided some relief after I stopped.
Thanks to Dr. Google, I was able to get a sense of what had happened.
I stopped running for several days, relying on the stationary rower and stationary cycle. On the first run I tried when I felt like I could handle it, I was heel striking for the first 1/2 mile or so. In retrospect, I got back to running too soon, because I failed the pinch test. However, I was able to run without pain, or at most, a few moments of soreness that would fade during the run. It wasn't until May or June that I could pass the pinch test, so I guess I'd say that my running didn't aggravate the injury, but it did retard the healing process.
From the summer of 2014 to May 2015, I had a largely injury-free block. And then in May, I ran a race that I refer to as "the world's longest 10K." Due to a miscommunication caused by race staff, we were misdirected about a quarter of a mile after the start of the race, and some of us had run 1 1/2 miles or more before being told we were off-course. I ended up running 9.5 miles that day. Although I stopped running at my 10K pace early on, I felt a recurrence of the dreaded Achilles pain afterward.
The tendonitis waxed and waned over the next several months. It was never debilitating enough that I couldn't run, but there were also few mornings that were entirely free from initial stiffness and aches. During the typical run, there might be anywhere from a few seconds to a few minutes of low-level achiness, and sometimes after running, the response to the pinch test would be more pain than before; other times, not.
It wasn't really getting worse, but improvement was marginal and slow. I decreased my weekly mileage slightly (well that was also in part because of some recurring family travel I had to do over the summer), going from my target of 150 miles/month to just under 130 miles/month for June-October. On October 31, I ran a double 5K race - first time as a regular 5K for speed, and then a second time through going through the optional obstacle stations. That aggravated my Achilles tendon, so November's total was just 88 miles.
As of now, my last run was a 10K race on Thanksgiving morning. Since then, I've rowed a ton on my Concept2, and my Achilles has been feeling steadily better. No morning stiffness or ache. It still feels a bit tender when I do the pinch test, so I'm exercising some more patience - better to take one more day off than necessary, than to get back to running one day too early. I don't know if I would be able to handle all this not-running if it weren't for that Concept2, though.