On some embodiments, a vertical stack of weights is disposed beneath a base member, and at least one selector rod is rotatably mounted on the base member and selectively rotated into engagement with a desired number of the vertically stacked weights. On other embodiments, a horizontal stack of weights is disposed on opposite sides of a base member, and at least one selector rod is movably mounted on the base member and selectively moved into engagement with the desired number of horizontally stacked weights. On still other embodiments, these two types of arrangements are implemented in combination. Various methods may be performed using various combinations of these arrangements to provide adjustable resistance to exercise. In one such method, a base member is lifted by grasping a handle that extends longitudinally between first and second weight engaging ends of the base member. The base member is positioned between first and second weight plates in such a manner that rails on the weight plates slide into slots defined in respective weight engaging ends to prevent the weight plates from moving longitudinally relative to the base member. First and second weight selectors are moved to positions that prevent the rails on the weight plates from sliding out of the slots defined in the respective weight engaging ends, and then the base member is lifted with each weight plate secured thereto.