This is a phenomenal core exercise targeting two distinct aspects of abdominal training. It's going to be build core support strength while also targeting the six-pack abs.

The first part will focus on the stretch...this is done with a simple dumbbell pullover movement. The second part is a "support," holding that same dumbbell in front of your chest momentarily, supporting in front of you (a.k.a. "anti-flexion" or bracing).

When combined, these two movements hit what amounts to a "stretch" and a "load" of the core muscles. It's incredibly effective and extremely challenging.

To do this one, you'll need a dumbbell and a bench (it can also be done on a Swiss Ball as well).

Set the flat bench up against something solid like a wall or machine so that it doesn't slide when you're doing the exercise. Use a moderately heavy dumbbell for this. I'm using a 95 lb dumbbell in the demo.

Sit on the end of the bench, grab the dumbbell and set it on end on your thigh. Grip the handle with both hands, using a "baseball bat" type of grip, one high and one lower. There likely will be some overlap in your hands, which is nothing to worry about.

This grip is going to allow you to transition between the two parts of the exercise without having to adjust your grip.

Shift your butt forward off the end of the bench. The end of the bench should hit you in the lower to mid-back area. This is the reason why you want the bench to be braced against something solid (if it's not, the bench might slide backwards here).

Use both hands to get the dumbbell to the top position.

Now do a pullover, lowering the dumbbell back and down until it touches the bench behind your head. Your elbows should be somewhat bent here. This position puts a nice stretch on the rectus abdominis (six-pack abs).

Now reverse the movement and perform a pullover to the top again. Continue the forward movement past vertical, dropping the hips down as you do so.

Bend your arms more, and come all the down into a full sit with the torso vertical. This is REALLY where you want to have your bench braced against something solid. Your feet are driving backwards to wedge you onto the bench while supporting the weight in front of you.

Your forearms should be close to your thighs, but just slightly off (hard to see in the pic) so the weight is not supported by the legs at all...just the core, shoulders and arms.

Hold for a second then powerfully reverse the direction (you can go a bit slower and more deliberate when using lighter weight...when heavier, you're going to need to use your legs and glutes to help).

Bring the weight up and back.

Then do another pullover.

Repeat until something gives out.

Likely this is going to be the "support" function of the core as the pullover is a stronger exercise/position in this combo. I recommend using this exercise for fairly low reps to get the most bang for your buck (i.e. 4-7 reps per set), though you can go higher rep if you like.

Perform 2-3 sets of this with about a minute rest in between sets.

This exercise is a KILLER for targeting the entire midsection. It's going to work your core strongly, while also bringing in the upper and the lower body as well.

Definitely watch the video of this exercise in action. It'll help you get the movement down so that you perform it properly.

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