Physical quality is determined by the comprehensive physiological conditions of muscles, bones and organs, which are divided into two aspects: physiological and psychological. Only lifting dumbbells can really improve physical fitness, but it only exercises the arms and shoulders, and at most increases the back. Immunity is regulated by exercise and diet, which basically depends on the amount of lymphatic factor in your body. I also often lift dumbbells. My muscles have grown and my strength has increased, but my spine can't stand it for a long time. If your body is not so tough, I suggest you exercise less and exercise more. At the same time, you should pay attention to healthy diet and keep a good mood, so that your physical fitness and immunity will come up!