A treadmill comprising: a frame comprising a first frame and a second frame arranged in parallel with each other; a plurality of slats movable with respect to the first frame and the second frame in a first direction and extending in a second direction perpendicular to the first direction; and a plurality of bearings disposed in each of the first frame and the second frame and supporting the plurality of slats to be movable in the first direction, wherein at least some of the plurality of slats comprise a base portion providing a first surface and a strength reinforcing portion protruding from the base portion, and the strength reinforcing portion comprises: a first reinforcing portion protruding from the base portion; and at least one second reinforcing portion extending in a direction intersecting a protrusion direction of the first reinforcing portion, the at least one second reinforcing portion providing a second surface; characterised in that: at least one of the following features (i)-(iii) applies: (i) the second reinforcing portion comprises: a separation region separated from the base portion; and a contact region located at each of opposite ends of the separation region, the contact region being in contact with the base portion; (ii) a cross-section of the first reinforcing portion, taken parallel to the first surface, has a zigzag shape or a shape of waves; and (iii) the width of the second reinforcing portion decreases from a central portion towards the opposite ends of the second reinforcing portion. a frame comprising a first frame and a second frame arranged in parallel with each other; a plurality of slats movable with respect to the first frame and the second frame in a first direction and extending in a second direction perpendicular to the first direction; and a plurality of bearings disposed in each of the first frame and the second frame and supporting the plurality of slats to be movable in the first direction, wherein at least some of the plurality of slats comprise a base portion providing a first surface and a strength reinforcing portion protruding from the base portion, and the strength reinforcing portion comprises: a first reinforcing portion protruding from the base portion; and at least one second reinforcing portion extending in a direction intersecting a protrusion direction of the first reinforcing portion, the at least one second reinforcing portion providing a second surface; characterised in that: at least one of the following features (i)-(iii) applies: (i) the second reinforcing portion comprises: a separation region separated from the base portion; and a contact region located at each of opposite ends of the separation region, the contact region being in contact with the base portion; (ii) a cross-section of the first reinforcing portion, taken parallel to the first surface, has a zigzag shape or a shape of waves; and (iii) the width of the second reinforcing portion decreases from a central portion towards the opposite ends of the second reinforcing portion. a first reinforcing portion protruding from the base portion; and at least one second reinforcing portion extending in a direction intersecting a protrusion direction of the first reinforcing portion, the at least one second reinforcing portion providing a second surface; characterised in that: at least one of the following features (i)-(iii) applies: (i) the second reinforcing portion comprises: a separation region separated from the base portion; and a contact region located at each of opposite ends of the separation region, the contact region being in contact with the base portion; (ii) a cross-section of the first reinforcing portion, taken parallel to the first surface, has a zigzag shape or a shape of waves; and (iii) the width of the second reinforcing portion decreases from a central portion towards the opposite ends of the second reinforcing portion. (i) the second reinforcing portion comprises: a separation region separated from the base portion; and a contact region located at each of opposite ends of the separation region, the contact region being in contact with the base portion; a separation region separated from the base portion; and a contact region located at each of opposite ends of the separation region, the contact region being in contact with the base portion; (ii) a cross-section of the first reinforcing portion, taken parallel to the first surface, has a zigzag shape or a shape of waves; and (iii) the width of the second reinforcing portion decreases from a central portion towards the opposite ends of the second reinforcing portion.