The problem is that curls work only one muscle group, while the triceps and shoulders contribute far more to creating firm, functional arms. Chair exercises work especially well because they provide stability while allowing you to strengthen the chest, shoulders, triceps, upper back, and core together. Chair Push-UpsWhenever someone wants to strengthen the backs of their arms, chair push-ups become one of my favorite recommendations. Seated Punch PressI like finishing with a movement that combines arm strength, shoulder endurance, and core engagement. Alternating punches performed with control strengthen the triceps, shoulders, and chest while gently elevating your heart rate.