Fix Back Hyperextension in the Split Jerk
In the split jerk, we’re looking for a solid trunk when we receive the bar—the spine neutral and everything braced forcefully. It’s common to instead see the lower back hyperextended, or abrupt hinging at the thoracolumbar junction.
Let’s cover the possible causes for the back to be hyperextended in the split and what to do about each one.
Limited Overhead Mobility
Limited shoulder and/or thoracic mobility is the most obvious problem. If the arms can’t move into position overhead freely, the back will extend more to rotate the whole upper body to bring the bar back into a position that can be balanced.
The solution is equally obvious: improve your mobility. You can also try a wider grip at least temporarily to reduce the demand on mobility.
Weak Abs / Poor Bracing
If your trunk isn’t braced adequately forcefully, and/or your abs aren’t strong enough, your back is likely to wind up hyperextended.
Trunk stability work should be included every training day to address all aspects through the week: flexion, lateral flexion, rotation, isometric, and anti-rotation for the abs, and extension and isometric stability for the back. You can also add jerk supports in the split position and jerk recoveries, focusing on proper position and forceful bracing.
The trunk should be pressurized and braced properly for all lifts, even the lightest warm-ups—like anything else, the more you do it, the better you get at it, and the stronger and more natural it will become.
Back Leg Straight
If the back leg in the split is straight, the hip flexors will force the pelvis to rotate forward and hyperextend the back. The back knee should be slightly bent both for better stability and to prevent this excessive pelvic rotation.
Pushing or Driving Forward
Pushing the bar or driving forward into the split position tends to make the back leg extend too straight and rotate the pelvis forward, but also forces the lifter to reposition the weight over their base to establish balance. This is usually done naturally by hyperextending the back along with trying to move the bar back farther overhead.
Inadequate Bar Elevation
Finally, if a lifter fails to drive and elevate the bar adequately, they’ll sometimes be able to still sneak into a split by essentially wedging themselves under the bar. Along with soft elbows, this typically involves the lower back hyperextending, as a way to “shorten” the body and make it fit.
Work on dip and drive mechanics, power and timing with push presses, jerk dips, and power jerks.