Listen to your description ... is it an arm? Mainly practice biceps and pectoralis major. Anyway, it's just the muscles of the arm ... just keep practicing, and practice if you have nothing to do ... My classmate has an excellent one who can do 100 or more, which is strong ... For example, I started doing 10 (40 kg), and then I can do more than 20 ~ 30 ... Then I stopped practicing and didn't persist ... Hehe.