Injured (right) achilles tendon doing CUH&H intervals on Jesus Green. Only thing out of the ordinary was that I decided to wear O shoes to the session because I thought some grip might help on the grass. At about that time I started adding short (track) intervals to my weekly long (grass) intervals and I strongly suspect that was a factor.
Took a few days off and ibuprofen. Did a bit of random stretching and strengthening. Sort of got better but problem recurred all summer. Managed my first sub-80 half marathon at Great North Run in the September and went to pieces - within a week had hurt back, hamstring and achilles was now very serious. Back and hamstrings healed with time and stretching. Achilles didn't. Took a week off. Not enough. Peak severity 4 - stopped me running completely and then hurt walking for about a decade. Took months mostly off while doing calf strengthening and stretching exercises. Sort of got back but it got bad again when I put in any effort.
Repeated cycle of [do a bit of light training, get keen again, train hard, cause achilles to flare up badly, take months off] at least five times in vicious cycle over years.
During this time went to FASIC in Edinburgh for advice. Physio got their colleagues through to look as she had never seen anyone with such an immobile foot. Read about achilles injuries. Allegedly most are caused by overpronation - hence orthotics help by supporting arch. A small proportion are 'clunk foot' - zero mobility and minimal pronation - no known treatment strategy...
Eventually dropped out. Did minimal running for years - a short jog was enough to bring the problem back. Got out of shape. Got annoyed at being out of shape. Started training on a rowing machine. Strangely, magically, several months later tendonitis cleared up completely in right foot. Now hurts only in left and lets me train if I keep up the rowing and avoid tarmac and intervals. Hopefully enough calf strength will eventually get rid of it in the left leg...
Some useful achilles tendonitis links:
For anyone else bored/fed up with achilles tendonitis enough to have scrolled to the bottom the things that work for me are:
1. Eccentric calf exercises, with additional weight (I use 25kg of salt in a rucksack, built up slowly over months)
2. Ice - often, but never before exercise
3. Calf flexibility
4. Using less cushioned shoes and changing them often
5. Orthotics with a slight heel raise
6. Rowing (if you are doing it right and pushing off with your toes, your calves are working in a position which is more stretched than running which helps).
If I stop 1, 2 or 3 it flares up again.
Several years off did not fix it. Stopping running risks losing the calf strength which is essential to fix it. It has never stopped hurting, it now just usually hurts an amount that is sort of sustainable and fine.
And you have learn to distinguish the painful feeling of your heel being ripped to pieces while you are breaking down scar tissue (which may make it better) from when you are making it worse.