A curved manual treadmill for the exercise of a user, comprising: - a frame extending along a longitudinal direction; - a first rotational shaft suitable to rotate about a corresponding first rotational axis transversal to the longitudinal direction of the frame; - a second rotational shaft suitable to rotate about a corresponding second rotational axis transversal to the longitudinal direction of the frame; - an exercise belt operatively connected to the first rotational shaft and the second rotational shaft, so as to generate an endless closed exercise path (P1, P2), the exercise path (P1, P2) comprising an upper portion suitable to interact with the user, and a lower portion facing a reference plane on which the manual treadmill lies, the upper portion having a set curved side profile along the longitudinal direction of the frame, so that a force generated by the user on the exercise belt generates the rotation of the first rotational shaft and the second rotational shaft causing the displacement of the exercise belt from the first rotational shaft to the second rotational shaft, characterized in that: - the exercise belt comprises a first outer surface suitable to interact with the user, when said first outer surface corresponds to the upper portion of the exercise path (P1, P2), and a second inner surface, opposite the first outer surface, the exercise belt comprising sliding means (8, 8') of the exercise belt with respect to the frame associated to the second inner surface, - the frame comprises constraint means of the exercise belt, between the upper portion and the lower portion of the exercise (P1, P2), to the frame, which are suitable to cooperate with the sliding means (8, 8'), when the second inner surface of the exercise belt corresponds to the upper portion of the exercise path (P1, P2) generated by the exercise belt, along at least one part of the upper portion of the exercise path (P1, P2) generated by the exercise belt, the constraint means being shaped so as to keep the curved side profile of the upper portion of the exercise path (P1, P2) generated by the exercise belt substantially equal to the determined curved side profile. - a frame extending along a longitudinal direction; - a first rotational shaft suitable to rotate about a corresponding first rotational axis transversal to the longitudinal direction of the frame; - a second rotational shaft suitable to rotate about a corresponding second rotational axis transversal to the longitudinal direction of the frame; - an exercise belt operatively connected to the first rotational shaft and the second rotational shaft, so as to generate an endless closed exercise path (P1, P2), the exercise path (P1, P2) comprising an upper portion suitable to interact with the user, and a lower portion facing a reference plane on which the manual treadmill lies, the upper portion having a set curved side profile along the longitudinal direction of the frame, so that a force generated by the user on the exercise belt generates the rotation of the first rotational shaft and the second rotational shaft causing the displacement of the exercise belt from the first rotational shaft to the second rotational shaft, - the exercise belt comprises a first outer surface suitable to interact with the user, when said first outer surface corresponds to the upper portion of the exercise path (P1, P2), and a second inner surface, opposite the first outer surface, the exercise belt comprising sliding means (8, 8') of the exercise belt with respect to the frame associated to the second inner surface, - the frame comprises constraint means of the exercise belt, between the upper portion and the lower portion of the exercise (P1, P2), to the frame, which are suitable to cooperate with the sliding means (8, 8'), when the second inner surface of the exercise belt corresponds to the upper portion of the exercise path (P1, P2) generated by the exercise belt, along at least one part of the upper portion of the exercise path (P1, P2) generated by the exercise belt, the constraint means being shaped so as to keep the curved side profile of the upper portion of the exercise path (P1, P2) generated by the exercise belt substantially equal to the determined curved side profile.