In the Summer, heavy perspiration may cause a loss of salt (Sodium), therefore leading to cramps. In the Winter, it is likely that you have too much salt, not too little.

Potassium is (in some ways) a balance to Sodium. Very few people get enough. Look for vegetables that are high in Potassium. Cut down over-salting foods in the Winter.

Exercise is needed, but be very conservative, especially as you get older. Walking a reasonable distance each day is great. Also steatching and aerobics are fine, but not classic weight-lifting. Even Arnold is looking more normal every year.