Nothing wrong with sissy squats-especially if you have knee issues.
Interesting Article: http://www.popularfitness.com/articles/squatting.html
From the above:
"...scientists in the Departments of Anatomy and
Kinesiology at the Karolinska Institute in Stockholm, Sweden,
have recently determined exactly what happens to the legs
during squatting sessions. Eight burly young national-class
Olympic weightlifters took part in the research. Average
body weight was 180 pounds, mean age was 19, and
typical one-repetition maximum during squatting exercise
was about 230 pounds...
The subjects tried four different knee-flexion angles while squatting:
(1 ) knees flexed to just 45 degrees, (2) knees flexed to 90 degrees,
(3) knees flexed more amply so that the back surfaces of the thighs
were actually parallel to the floor, and (4) knees flexed fully
(the deepest-possible squat). The first two squats - 45 and
90 degrees - are actually just partial squats, with athletes remaining
in a semi-standing position and the buttocks only slightly lowered
toward the floor. Among coaches, there's considerable controversy
about which form of squatting is actually 'best' for athletes.
Video-taping and electromyography were used to determine joint
forces and muscle activity. As it turned out, the 45- and 90-degree
squats did a poor job of activating the quads and hamstrings, compared
to the parallel and deep squats. However, the former two squats also
produced fairly low forces at the knee and hip joints, so the 45- and
90-degree squats are probably excellent exercises for athletes who
are attempting carefully to recover from leg injuries.
Surprisingly, there was no difference in muscular activity between the
parallel and deep squats, even though coaches tend to recommend
the latter. The total times required to perform parallel and deep
squats were also similar, so neither exercise provides more total
work for the leg muscles per training session.
Although the parallel and deep squats produce equivalent amounts
of muscle activation, the parallel exercise is better for athletes who
have suffered from knee problems, since it produces less strain on
the knees. Athletes with hip problems probably should rely on
90-degree squats, since both parallel and deep squats upgrade
hip-loading forces significantly.
Overall, squatting does a great job of activating both the quads
and hamstrings, especially if one uses parallel or deep squats. Parallel
squats are as good as deep squats at working the muscles and better
than deep squats for limiting the risk of knee injuries."