Exercise apparatus having a slidable weight bar assembly with hand brake assemblies is provided for enaging and disengaging the weight bar assembly with a support frame. The exercise apparatus can be configured as a squat machine or a bench press. The exercise apparatus can include an adjustable back support that facilitates proper positioning and support of the operator's upper and lower back while performing squat exercises. The exercise apparatus can further include spring assemblies that increase the kinetic load during downward movements of the slidable weight bar assembly.