Treadmill

The treadmill is an object in The Sims 2 and The Sims 3 used to improve a Sim's Body or Athletic skill.

The Sims 2
The Fearless Flyin' 4000 Treadmill is an exercise machine introduced in The Sims 2: University. Sims can run on it until they become fatigued. When placed on community lots, it differs from other exercise machines in that uncontrolled Sims can and will use it. While it is most commonly seen on community lots, the Tinker family of Bluewater Village will have one if both University and Open for Business are installed.

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. Sims who exercise on the treadmill often become slimmer. Treadmills are commonly found in the gym and academy lot types, alongside weight machines (and in the latter case, Board Breakers and Sheng Hai Training Dummies).

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