So talking about arms …
A dancer has choices when it comes to moving her arms and where the initiation starts for that movement.
1. Arm Muscles: The biceps and the triceps are often the first muscles that beginning dancers use to lift their arms. They also tend to use many of the muscles in the shoulders (deltoids). The problem is these muscles are weak compared to other muscles of the body (especially on most women). Using these muscles to hold the arms up leads to quickly becoming tired and have the arms sink into those ugly dead bird arms (we see too often). For more experienced dancers these muscles are use often used for the more subtle movements completed by the arms.
2. The upper back muscles: This is one of the best ways to lift the arms, because the back tends to be much stronger then the shoulder or arm muscles. The arms can be held by a combination of the large trapezius and the smaller infraspinatus, teres minor and teres major(also called rotator cuff). The three smaller muscles work as a group to control the movement of the arm, shoulder and shoulder blade. Using these muscles also gives a stronger base to the hold of the arms.
How do you use your back to hold your arms? Things to try:
1. You can start by holding both arms out to the side (for a while) and seeing which muscles become sore first. If it is your arms and shoulders, than you need to work on engaging your back.
2. Bring your arms slightly forward. To properly engage your back muscles the arms can not be straight out to the side. The arms should be forward enough the if you wiggle your fingers they are visible in your peripheral vision, but not so far front that they can be seen straight on. It takes a bit of practice to find the right angle. Once you are here you can start using your back muscles.
3. If you have the flexibility then put your hand on your opposite shoulder blade and feel it move. Lift the other arm and see if you can feel the back muscles engaging. You want to feel your shoulder blade moving down and in towards the body. At the same time the arm should lift up and out.
4. Practice, Practice, Practice! Once you find how to engage from the back practice it until you develop the muscle memory and don’t need top think about it any more. Keep working and you will get there.