poohbear said:It's a very dangerous squat, especially for the beginner. The video shows that time is taken before the butt touches the box, but this is usually where beginners or inexperienced lifters make their mistakes. Unlike regular squats, box squats have two forces pushing towards the midline from opposite directions. Regular squats has the weights (and gravity) pushing down, but the box has the weigths pushing down and box pushing up (or stopping the motion). It causes too much pressure on the spine, creating a movement similar to an acordian. I'll dig up my books and cite references for you, but that is one reason I know of.
A SMITH MACHINE SQUAT is a DANGEROUS SQUAT! A box squat, IF, done correctly is not dangerous. When you box squat right...you sit BACK (not down) far enough that yoru shins are past vertical...this takes all the pressure off the patella tendon. And overloads the hips, glutes and hamstrings...the prime movers of a BIG squat.
Also you SIT on the box...you dont FALL on the box. If a beginner cannot control the eccentric portion of the lift then we have them use a higher box until there hamstrings are brought up. When on the box...you keep everything tight...you relax the hip flexors and then reflex them. "This will cause the spinal erectors to instantly flex, which activates the hips and then the hamstrings. The action is like doing a jerk in Olympic lifting."
One last point....the weights we use on box squats are percentages of a 1RM for 2 reps. Think of the different TUT between that and a conventional squat with near maximal weight...on a consistant basis. The muscular soreness is much less than with regular squatting.
http://elitefts.com/documents/box-squat.htm