Smith-Machine
Squat 
The
smith-machine squat seems to be a favorite of
many, unfortunately often to the exclusion of
free-weight squats. One big disadvantage
is the many complaints of knee and hip pain:
Because your body is locked into the machine's
groove, it can't move in the most natural way.
Even with your feet and knees out in front of
your body—where
they must be with normal foot width to avoid
excessive forward movement of your knees during
the negative portion of the squat—your
knees are still exposed to a high level of shear
stress.
If
you do this exercise only rarely, it can
substantially reduce the need for balance and
stabilization. The way there usually
performed—with
your hips under the bar and your feet about a
foot in front—reduces
the involvement of your hip and hamstring
muscles. This might be just what a
bodybuilder wants, though reduced stabilizer
work means this squat variation isn't the best
for athletes is sports other than bodybuilding.
The
huge advantage of the smith-machine squat are:
One, it allows you to squat hard and heavy,
including going to failure, without spotters.
Two, it offers many options of foot placement,
which can help you feel your body in various
ways, stress your thigh muscles differently from
the basic squat and possibly allow you to take
your hams and glutes somewhat out of the
equation.
