Manually powered treadmill

A manually powered treadmill comprising:

• a frame having a front end and a rear end positioned opposite the front end;
• a rotatable element coupled to the frame;
• a plurality of bearings coupled to the frame;
• a running belt at least partially supported by the rotatable element and the plurality of bearings, wherein the running belt includes a front belt portion proximate the front end, a rear belt portion proximate the rear end, and a central belt portion intermediate the front and rear belt portions, wherein the central belt portion is positioned vertically closer to a ground surface supporting the frame than at least one of the front and rear belt portions such that at least a portion of the running belt follows a substantially curved running surface;
• and
• a safety device comprising an inner element and an outer element, the safety device substantially preventing rotation of the rotatable element in a first rotational direction of the rotatable element and permitting rotation of the rotatable element in a second rotational direction of the rotatable element opposite the first rotational direction, wherein one of the inner element and the outer element is substantially prevented from rotation relative to the frame in the first rotational direction and freely rotates relative to the frame in the second rotational direction.

A manually powered treadmill, comprising:

• a frame;
• a front rotatable element coupled to the frame;
• a rear rotatable element coupled to the frame and spaced a distance from the front rotatable element;
• a running belt at least partially supported by at least one of the front rotatable element and the rear rotatable element, wherein the running belt defines a running surface, at least a portion of which is curved;
• and
• a safety device coupled to at least one of the front rotatable element and the rear rotatable element and comprising an inner ring element and an outer ring element, wherein the safety device is structured to substantially prevent rotation of the at least one of the front rotatable element and the rear rotatable element in a first rotational direction and permit rotation of the at least one of the front rotatable element and the rear rotatable element in a second rotational direction opposite the first rotational direction.