Abstract: An aerobic conditioning apparatus for use by a trainee in simultaneously exercising the upper and lower body in a smooth shock-free manner substantially simulating movement of the arms and legs during swimming. The apparatus includes a supporting frame, first and second foot supporting assemblies mounted on the supporting frame for controlling the movement of the right and left feet of the user respectively to an oscillatory motion along first and second paths between first forward positions and a second rearward position, first and second hand engaging assemblies mounted on the supporting frame for controlling the movement of the right and left hands of the user respectively to an oscillatory motion along paths between a first upraised position and a second lowered position, and synchronizing mechanisms mounted on the supporting frame for causing synchronous movement of the foot engaging assemblies and the hand engaging assemblies.