1. Back: Hard pulling mainly exercises the muscles of the back, including latissimus dorsi, trapezius, erector spinae and gluteus maximus. These muscles are essential to keep the spine stable and support the upper body.

2. Legs: Although hard pulling mainly exercises the back, it also exercises the muscles of the legs, such as the quadriceps femoris on the front side of the thigh and the gluteus maximus on the back. These muscles play an important role in the hard drawing process.

3. Core: Hard pulling needs to maintain the stability and balance of the body, so it is also very effective for the training of core muscles. The core muscles include the muscles of abdomen, waist and buttocks, which play a supporting role in the process of hard pulling.

4. Arms: Although hard pulling mainly exercises the muscles of the back and legs, it also exercises the muscles of the arms, such as biceps and triceps. These muscles play an auxiliary role in the hard drawing process.

5. Shoulder: When pulling hard, the muscles of the shoulder also need to participate, especially the deltoid and deltoid muscles. These muscles play an important role in keeping the shoulder joint stable and providing strength.

In a word, fitness stretching is a comprehensive exercise method, which can exercise all parts of the body, especially the back, legs, core and arm muscles. At the same time, it can also enhance the stability of the spine and improve the sports ability.