The main thing that thickens the arm is to exercise the triceps. Push-ups can exercise pectoralis major, triceps and deltoid muscles, which is a good compound action. If the distance between the palms is shortened, you can exercise the triceps better. In addition, the parallel bars arm flexion and extension is also a compound movement, which exercises the lower edge of the chest, as well as the three heads and triangles. Another good isolated action of exercising three heads is the flexion and extension of the back arm of the chair and stool. This action can be practiced with two chairs.

As for biceps, you can also exercise properly. Various bends are a good way to exercise the head in isolation, but it is not easy to practice without dumbbells. But as long as you have the horizontal bar to do the reverse grip pull-ups, it is also very good exercise for your head. As for deltoid muscle, it is also very important. You can practice deltoid with push-ups and parallel bars.

Do these simple actions, and your arms will become very developed.