Because you have to understand the principle of muscle growth, that is, excessive recovery. During muscle exercise, some muscle fibers will break (of course, it will not be serious, but it is strain). Muscle fibers will repair themselves after exercise, and the repaired muscle is larger than the original, so the muscle is bigger. When exercising without load, the muscles will gradually become smaller, but fortunately, the muscles have memory, and when exercising again, they will be much faster than last time.

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