Abstract: A treadmill exercising device comprises a rigid frame having spaced first and second side members and front and rear end members with a plurality of rollers positioned laterally across the frame. The rollers are rotatably supported in plate members affixed to the side members and have opposite end portions, one of which has an end cap so as to provide a longitudinally extending series of end caps. An endless belt extends longitudinally of the frame along the first side member in contact with the series of end caps in driving engagement whereby rotation of several of the rollers rotatably drives other of the rollers in unison therewith. A braking carriage is slidably mounted to the first side member and has a plurality of grooved wheels rotatably mounted therein. The braking carriage is positioned adjacent the aligned roller end caps and the grooved wheels engage the belt.