“There are a huge number of possible causes for problems with the jerk. Since this question explicitly asks about both strength and technique, yet doesn’t describe any specific issue, I’ll try to cover both topics in a general sense without being so vague it’s useless. Eventually I’ll try to remember to actually answer the question about lifting from the front or back.
With regard to strength, we might consider it in four different areas: leg strength to achieve the upward acceleration of the bar; leg strength to support the weight in the receiving position and recover; upper body strength to support the weight in the receiving position; and upper body strength to drive the athlete under the bar (and drive the bar up slightly as well).
Leg strength for the upward drive of the bar will essentially be a product of squatting strength, more specifically the front squat as the drive of the jerk is primarily achieved by the quads. If general squatting strength is good, but the drive of the jerk appears weak, it can be addressed more specifically. Partial front squats, jerk dip squats, jerk drives, and jump squats can all be effective in this case. Consider trunk strength as well – softening of the trunk during the dip and drive of the jerk can absorb a significant amount of the upward force and render good leg strength ineffective.
Inadequate length strength in the split receiving position can either mean an inability to support the weight that’s been jerked, or it can actually prevent the lifter from getting into a sufficiently deep split position as weights increase. Again, squatting strength is the basis, but athletes can have surprising strength deficits in a split position. To address this, any number of single-leg squatting or lunging exercises can be used, but I do have some favorites. The basic lunge is the first simply because it’s simple and easy to teach and there are many options for loading it safely. Next is an exercise I picked up from former Polish coach and current USA OTC resident coach Zygmunt Smalcerz. With a barbell on the back as it would be for a back squat, the lifter will step out into his split receiving position, making sure to maintain proper balance between the front and back feet, holds this momentarily, then steps forward into a split position with the other leg forward. Essentially this is a walking lunge, but rather than a typical deep lunge, the position is identical to the split jerk receiving position. This exercise can be done with very heavy weights – as much as 100% or more of the lifter’s best jerk.” Continued…