As I've said in the past, who doesn't love a new core exercise? Enter the PUPP with Three-Ways Slider!
I'm almost positive I'm not the first one to come with this type of variation, but I haven't seen it anywhere else, so I'll take the credit for now. This is a variation on the PUPP with alternating hand slide outs (which you can see HERE).
Instead of merely sliding out forward, you add in a lateral and backwards (towards your toes) slide too.
This is a superb exercise to train the anterior (front) core in resisting extension, rotation, and teaching overall stabilization of the lumbo-pelvic region (lower back and hips). It also throws in a side order of training the shoulder stabilizers (think rotator cuff) and encouraging the shoulder blade to move around on the rib cage.
Things to Remember:
1. Keep your abs and butt tight. Not simply I'm-kinda-squeezing but seriously crush your muscles together. This will stabilize your hips and spine to prevent errant lateral movement as well as saggy hips. Saggy hips = angry spines.
2. Maintain some pressure on the moving arm's slider, but not so much that you can't slide it. You can either do all the reps on one arm and then switch or alternate as you go between reps. I prefer to do all one side then the other since you'll have a decent amount of time under tension- thus building up some endurance in the core and shoulder muscles- but I think in the grand scheme, it matters not.
3. Ensure that your supporting hand is directly under your shoulder. If it's too far in front of your shoulder, you'll likely lose your balance as your hand will slide out from under you. If it's too far behind (in the direction of your toes) you'll end up with a rather cranky shoulder by the end.
4. If you have trouble stabilizing your hips, spread your legs outside shoulder-width to create a larger base. As you become more proficient, you can scoot your legs closer together.
Aim for 6-10 reps per side and 2-4 sets.