Well, I've checked my books, which fortunately are consistent.
Problems with Achilles' tendons usually cause extreme stiffness first thing in the morning which gradually improves as movement warms & loosens the calf. When running it usually improves as you continue, which gives a false sense of security.
Causes can be:
Sudden dramatic increases in mileage or intensity
Running in sand (!)
Tight calf muscles
Overpronation
Frequent wearing of high heels (shortens calf muscles) so when you switch to trainers your Achilles & calves are forced to stretch quickly
I also looked up general calf pain. It's defined as inflammation in the muscles of the calf. Symptoms can include pain & tenderness, tightness & possible swelling.
Causes can include:
Sudden dramatic increases in mileage or intensity
Lots of running on hills or uneven surfaces
For both conditions treatment is similar:
RICE
Ibuprofen
Stretch followed by ice (particularly to reduce tendon irritation
Wear street shoes with low heels
Only run if it doesn't hurt
Cross-train to maintain fitness, may include elliptical trainer, swimming etc
If it doesn't improve, get help !!
Hope things get back to normal soon, take care.