Treadmill

The Treadmill is an object in The Sims 2 and The Sims 3 used to improve a Sims Body or Athletic skill.

The Sims 3
The Shut-In Treadmill is the default treadmill for The Sims 3. Sims can run on it until they become fatigued. It increases the Athletic skill, specifically the cardio (as opposed to strength) aspect of a Sim's fitness. Sims with high Athletic skill can train other Sims on this object.

The Sims 3
The Slimline Axursize is a high-tech treadmill introduced in The Sims 3: High-End Loft Stuff stuff pack.