Dumbbell curls can strengthen the biceps, but the shape and strength of the arms also depend on the triceps, shoulders, upper back, and chest doing their share of the work. When I coach older adults, I’m looking for upper-body exercises that build strength without making the shoulders feel cranky. Muscles Trained: Chest, shoulders, triceps, core. Lateral Dumbbell RaiseLateral dumbbell raises train the sides of the shoulders, which can help the upper arms look more defined and supported. Train the back of the arms, shoulders, chest, and upper back together, and your arms have a better chance to feel stronger, firmer, and more capable.