Its detractors argue that the "natural" motion produced by movement of the body' s limbs is rotational and that the two are therefore incompatible. This argument is completely erroneous because it fails to consider that regardless of the path through which the load is moved, the motion of the limbs about the axes of the joints remains rotational in nature. This is because the limbs are not capable in general of active linear motion (though one portion of the body may be moved passively through space on a linear path it is as a result of rotational motion occurring about the axis of another joint e.g. the forearm and hand may be pulled directly towards the body on a linear path via rotation at the elbow and shoulder). Muscle complexes are activated to produce linear forces that act on bones via connective tissue. The linear muscle forces are translated into angular torque by the lever systems formed through the articulation of the bones, and expressed as rotational movement (provided there is a net unbalanced force present) of the limbs about the joint axes. Several of these rotational movements can then be combined and coordinated to produce a variety of external movements both linear and rotational in nature. The squat for example (whether using a barbell or a Smith-machine) is a combination of rotational movement at the ankle, knee, and hip joints, with minimal spinal deflection at the articulation with the pelvis. The nature of the final overt movement that is expressed in no way alters the rotational nature of the movement of the limbs about the joint axes that combine to produce it.