Form the hand of the arm your want to flex into a tight fist. The simple action of forming a fist already begins to tighten your muscles. It's impossible to fully flex your arms if you don't make a fist first., Straighten your arm either downward or out to the side. This lets the arm start at its most expanded state. Starting with a straight arm and a fist gives you the best ending result.
 Raise your hand upward and bend your elbow. Go slowly so the tension builds through your muscle as it tightens. Focus your energy into tightening the muscles in the arms. Hold the position to showcase your muscles. Don't hold a flex for too long before you release it.
Make a fist.
Extend and tense your arm.
Bend your elbow slowly to tighten your bicep.
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