If you don't have a safe, fenced area for them to exercise off leash while outside then the dog should remain on leash at all times. (foxterrierrescue.net)
This may knock a few exercises off your list. (kingofthegym.com)
Of course, this won't rob the cardio exercise off all its health improving benefits, but it won't trim down your waistline either. (fitnessandpower.com)