Here is Rick Demonstrating Plank Rows, one of the October Five Exercises. With this move you strengthen your upper body, core, back, legs, just about everything!
Notice how he stabilizes his back and hips while lifting one hand.
This is the most challenging variation of this move (believe me – he is making it look easy).
You can also do this sans weights. Start in a plank position with knees down. Make sure your ear, shoulder, hip and knee make one line (look in a mirror if you need to). Now slowly lift one hand and lower it back down. Now try this with a 5 or 8 lb weight. In the photos Rick is holding the weights the whole time. If this bothers your hands or wrists place your hands flat on the ground instead and pick up one weight at a time.