The present invention relates to a treadmill. The treadmill includes a treadmill frame, an endless belt, a strap member and a retracting device. The strap member is located above the endless belt. The strap member has a first end, a second end, and a middle section. The first end of the strap member is operably connected to a right side of the treadmill frame, and the second end of the strap member is removably connected to a left side of the treadmill frame. The retracting device is configured to retract the strap member into the retracting device when the second end of the strap member is disconnected from the treadmill frame. When the second end of the strap member is connected to the left side of the treadmill, the middle section of the strap member constrains a position of a user on a top surface of the endless belt.