the stretcher has a certain effect on shoulder training, mainly to the deltoid and trapezius muscles. Long-term training will have a certain effect on shoulder width, but if only the stretcher is used, the effect may not be obvious, because the tension of the stretcher is limited and the training effect cannot be guaranteed for a long time.
If you want to practice your chest muscles and shoulders, the simplest plan:
1. Push-ups, 2. Flexion and extension of parallel bars, 3. Pull-ups, 4. Farmer walking (that is, walking with heavy objects in both hands).