Today we were using the free curriculum from Mr Q Science to learn about skin, muscles and bones. We made this model arm to show how muscles work.
You'll need 2 card strips (arm bones) joined together with a brad (ligament), attach a piece of string (muscle) to the lower arm using a paper clip (tendon). Attach the other end to to upper arm bone with another paper-clip (tendon) but make sure this one can be pulled through.
Work the arm by pulling the string (muscle) and the lower arm will raise. You can see how the muscle shortens. You cannot lower the arm by pushing the string - muscles only pull. A real arm has another muscle that will pull the arm back into a straight position. Maybe you could make one with this muscle too.
|Cut out a hand shape for more realism|
Pull the muscle to raise the arm - like this: