TRICEPS. Are allll that.
You probably know that your triceps muscle is the large muscle on the back of the upper arm.
What you might not know is that the triceps is actually the LARGEST muscle in your arm: it has three points of attachment since it is longer than the biceps, which has only two.
IT ONLY OPERATES when you straighten your arms from bent. NOT the other way which is your bicep (curl).
THIS MEANS: your jiggly stuff will ONLY go away when you intentionally work it or throw a ball or pla