exercising

1. To exert for the sake of training or improvement; to practice in order to develop.

   to exercise troops or horses;  to exercise one's brain with a puzzle

2. To perform physical activity for health or training.

   I exercise at the gym every day.

3. To use (a right, an option, etc.); to put into practice.

   She is going to exercise her right to vote.

4. (now often in passive) To occupy the attention and effort of; to task; to tax, especially in a painful or vexatious manner; harass; to vex; to worry or make anxious.

   exercised with pain

5. To set in action; to cause to act, move, or make exertion; to give employment to.

noun

The act by which something is exercised.