I saw this exercise and i cant remember where but it is a chest exercise, You lie down on floor, put dumbbell on your chest, grab it firmly with both hands in middle and raise it to top and them back again to chest and so on. I this exercise legitimate and is it effective for chest?
I think this video (@5'30) describes the exercise you want. It also describes the way you can use it to target the chest. One exercise can target different muscles depending on how you use it i.e. changing little details can change the targeted muscles