In order to build strong muscles, scientific and systematic strength training and reasonable diet can be carried out. As a student now, the exercises that can be done now are generally push-ups, pull-ups, parallel bars arm flexion and extension, sit-ups, dumbbell training and so on. Here is a simple distribution for you:
Push-ups on the first day 15-20 *3 group
Parallel bars arm flexion and extension 8- 12 *3 groups
8- 12 *3 groups of flexion and extension of dumbbell neck and dorsal arm
Lumbar and Abdominal Training 10- 15 *4 Group
The next day, 8- 12 pull-ups *3 groups.
Dumbbell and platoon 8- 15 *3 groups
Dumbbell bend 8- 12 *3 group
Waist and abdominal training as above.
On the third day, sit on the dumbbell and choose 8- 12 *3 groups.
Dumbbell side lift 8- 10 *3 groups
8- 10 dumbbell *3 groups.
Squat with bare hands (best load) 15-20 *4 group
Bow and arrow squat 10- 15 *3 group
Waist and abdominal training as above.
Rest on the fourth day.
Circulate in the above manner. Eat high-quality protein (such as beef, chicken, egg white, etc.). ) on the diet.
To add my own opinion, you are only 15 years old, and the functional development of all aspects of your body is still not perfect, especially the bones are in the stage of developing length, which will gradually thicken with age. The body is influenced by parents. Naturally, some people are born with strong bones. Don't pay too much attention to these natural things. If you care too much, it will shake your confidence in exercise and reduce your enthusiasm for exercise. Besides, you should concentrate on your study now. High-intensity strength training will consume too much energy. Therefore, at this stage, you should adhere to the above methods and means to lay a good foundation for yourself. When you are an adult, more systematic and scientific training will have very good results.