While your bodyweight is one hell of an exercise tool, there are some upper-body muscles that are best challenged with external resistance, like dumbbells. you can work your triceps and chest by doing "push" movements, like push-ups and triceps dips. You can challenge your shoulders with pretty much any plank move. But your biceps and back muscles respond best to "pull" movements, for which you need something to work against. That's where this dumbbell arm, chest, and back workout comes in. ~ Berceste