SkeletalMusclesTorsoArm460Most muscles are connected to bones.

relax2contract460Muscles move our bones by contracting and relaxing.

relax1contractWhen muscles contract, they get shorter, and when they relax, they get longer.

BicepsTriceps3ContractRelax460The biceps and the triceps come in pairs and work together.

BicepsTriceps1ContractRelax460When the biceps contract, the triceps relax. When the triceps contract, the biceps relax.

BicepsTriceps2ContractRelax460When we bend our arm, our biceps contract and our triceps relax. When we stretch our arm, our triceps contract and our biceps relax.

Video | Jared uses a great arm model to show us how muscles move bones. Via FunScienceDemos!