Today we are going to hit the glute-ham developer (GHD) sit up. It's a great exercise to develop hip flexor strength, which is relevant to many other movements done in CrossFit. It's important to have the proper mechanics when doing these, lest you hyperextend the back and consequently experience back pain-which does not set you up for success.
The video below features Matt Chan, six-time CrossFit Games competitor and owner of CrossFit Verve (Denver, CO), going through the movement. He demos two variations- he goes to parallel and the second, to beyond parallel (full range of motion).
Many people express that they have back pain when executing this movement- a couple things to keep in mind are:
- Hyperextension of the spine is the basis for back pain in many people
- Keep spine in neutral with ribs tucked will mitigate hyperextension
Set up- Hips slightly off the pad (butt off pad) and knees slightly bent
- Parallel variation
- Go to parallel
- Drive the leg straight- this engages the rectus femoris (More discussion on this)
- Sit up
- Beyond parallel/Full range of motion variation
- Ride as low as you can until you feel that you are about lose the neutral spine position
- Drive the leg straight
- Sit up
"Rectus femoris is the top piece of the quadriceps and it both extends the leg and flexes the hip. Rectus femoris originates at the pelvis and attaches to the patella via the patellar tendon. In the sit-up rectus femoris pulls the athlete to seated from both the pelvis and the iliac spine..." - Greg Glassman in Glute Ham Developer Sit Up
Activation of the rectus femoris is important because 1. it adds significant force to the sit up and 2. it reduces the shear force on the lumbar vertebrae by pulling from the pelvis and iliac spine instead of the lumbar spine.
Try it out and if you've had back pain associated with this movement, try just sticking to the parallel variation. You'll still have the benefits of the movement without the low-back stress.
A1. 4x 3+6 strict pull ups + kipping pull ups
A2.4x 12 GHD sit ups
1 min ME Burpees
Rest 1 min
1 min ME Row for cal
Rest 1 min
30 secs ME Lunges
Rest 30 secs