He used ... A lot when he in the country 1.

1) He used to swim a lot when he lived in the country.

We used the expression used to to denote a habit, frequent action in the past. This expression is never used for present habitual actions but only for regular actions in the past. NB: dont mix up the expressions used to do something and to be used to doing something. They have completely different meaning, though they may seem similar to you.