Do arm exercises make your arms longer?

There has been some speculation about that. In general, the common wisdom says that you can't do anything to change your height or the length of any long bone, that it's all already programmed when you're born. But the reality is, we're all growing until the "growth disc" closes. The growth disc is the area of our bones, near the ends, where "long" bones actually grow longer. Once the growth disc "closes" or ceases to function, you have reached your maximum height. Growth discs close usually a little after we start puberty.