So here is Uber-trainer, Rob Miller, demoing some good and bad form faults. Once again, we must be doing something right since those that answered hit the nail(s) on the head. In each of the pix, Rob has dipped down to create the momentum from the subsequent upward drive to propel the bar up and overhead.
In pic #1, Rob is in a nice position. The elbows could be up a tad higher, however, I think this may be due to the lackof weight of the PVC. Getting the elbows up to a partial front rack without any substantial weight is tough. But, if the bar were weighted, I’d like to see the elbows placed up a bit more. This would allow the bar to sit on the front caps of the shoulder, thereby relieving tension in the wrist and allowing energy transmission from the legs to travel directly up the body and into the bar to create upward movement. If the bar is held out front in a strict press grip, some energy is lost as the arms acts as shock absorbers and don’t properly transmit the energy.
Otherwise, the dip is ideal. The torso is vertical and the ass is directly over the heels, thereby placing the weight solidly across the foot for maximum return of energy and stability. The dip is also short enough to generate quick power. The dip must be done quickly and violently to use the reflexive properties of the musculoskeletal system via the Stretch Shortening Cycle. Up, down fast!
Pic #2 is no bueno due to the forward inclination of the torso. This is common with people since many folks want to initiate the dip with a movement similar to how the squat is initiated. We never initiate a squat at the knees, instead we start at the hip and get them back and place the weight onto the heel. In a Push Press or Jerk, the dip is vertical and is intitiated by the knees. This keeps the torso upright and the movement snappier. If the torso is leaning forward, weight will be on the toes and the athlete will be off balance, the wrists will be loaded, and the bar will shoot out that direction and most likely cost you the lift with any weight of consequence on the bar.
In Pic #3, Rob is showing us what is commonly called a “muted hip”. This means the hip is in line with the femur. There is no energy return of any use from this position. The energy cannot travel up the body properly and gets lost. Additionally, at heavy loads this can be injurious by causing compression of the discs in the lumbar spine as the back is going into hyper-extension. This position is seen when athletes get tired and push their butt/hips forward instead of down (remember my term, “put your ass on your heels”). Midline sability is gone and things get loose, next thing you know you look like the victim of a bad prison shower incident. If the weight does get up, there is an issue of instability as the athlete tries to re-center themselves under the bar to support the load and properly lock it out. Wasted effort through lousy mechanics.
So, once again nice job on picking up on the subtleties of good/bad movement! Once you see it, you can often self-correct when you feel these things happening to you, or better yet, help someone else out when you see them do it.
Go forth and conquer!