Some of the most common causes of tight calves are possibly having a biomechanical issue with your running gait, increasing your mileage by too much too soon or by running in snow or on ice.
To see if you have a biomechanical problem with your running, go to a qualified running store. Many running stores have a treadmill in them where they will watch you while you run. If they don’t, they will watch you run to see if you have a problem with your form. If this is the problem, they can make sure you are wearing the correct type of shoes. Or, you may need to wear a special insert/orthotic in your shoes.
As far as training mileage, make sure that when you are increasing your mileage for a longer race or after a layoff correctly. Only increase your mileage by 10% from one week to the next. For instance, if you are running 20 miles a week, only increase your mileage next week by 2 miles.
When the roads are slick from snow or ice, runners have a tendency to shorten their stride and will cause you to run different than you normally do. This change in your gait can cause tight calf muscles.
To help relieve tight calves, stretch out your calves after your run. One of the best is one that I’m sure you’ve seen done. Place your hands on a tree or wall – arms should be extended. Lean with one leg bent and the other one extended back with your knee straight. Keep the heel of the rear foot flat and feel the stretch on your calf. You should feel the stretching of your calf. Hold this for about 30 seconds and then do it with your other leg.