Treadmill

A treadmill, comprising:

• a base allowing a user to run or walk;
• a first frame arranged under the base and pivotally coupled with a front portion of the base, comprising:
• a lateral stick;
• and
• two side sticks being respectively arranged at a left and a right side of the lateral stick and being coupled with the lateral stick, each side stick comprising two ends, in which one end includes a first wheel against a ground and the other end pivotally couples with a pivot portion of the front portion of the base;
• a second frame arranged under the base and pivotally coupled with a rear portion of the base, comprising:
• an outer frame to contact with the ground;
• an inner frame being arranged within the outer frame and being pivotally coupled with the outer frame, the inner frame comprising:
• a lateral bar;
• and
• two longitudinal bars being respectively arranged at a left side and right side of the lateral bar and being coupled with the lateral bar, each longitudinal bar comprising two ends, in which one end pivotally couples with the rear portion of the base, and the other end comprises a second wheel to movably couple with the outer frame;
• and
• a driving assembly movably coupled with the lateral stick of the first frame and the inner frame of the second frame;
• wherein the driving assembly comprises a tube moveably coupled with the lateral stick of the first frame and the lateral bar of the inner frame, and when the tube moves toward the front lateral stick of the first frame, the second frame is lifted so that a height of a rear portion of the base is greater than a height of a front portion of the base;
• and when the tube moves toward the lateral bar of the inner frame, the first frame is lifted so that the height of the front portion of the base is greater than the height of the rear portion of the base.