That's how Men's Health fitness director Ebenezer Samuel, C.S.C.S. makes the most of this arm day workout. He takes a single-arm skull crusher—an exercise that typically isolates the triceps—and adds a healthy dose of balance and anti-extension action that makes your core work overtime to keep yourself stable.
"The half-bench skull crushers are cancelling out one of the main things people are sloppy with on skull crushers: If they don't have great shoulder range of motion overhead, they compensate by arching their back," Samuel says. "From that half-bench posture, you can't really arch your back, so your purer shoulder mobility comes out."
To perform the half-bench skull crusher, you'll need a sturdy bench and a light to medium weight dumbbell. Check out this adjustable option from Bowflex if you don't have a set handy.