Over 70 years old will have no physical strength may be malnutrition, respiratory diseases, tumors, etc., need to be specifically analyzed. 1. Malnutrition: the metabolism of the elderly will slow down, the muscle mass will decrease, the digestive function will be weakened, at the same time there may also be poor appetite leading to a reduction in the amount of food and drink, so the elderly will be more likely to malnutrition, which can be manifested as a lack of physical strength, biochemical tests can be used to assist in the definitive diagnosis. 2. Respiratory diseases: if there are respiratory diseases such as chronic bronchitis, chronic obstructive pulmonary disease, etc., long-term lung disease will lead to chronic hypoxia, so there will be a lack of energy, chest CT, lung function and other tests can assist in clear diagnosis. 3. Tumor: Tumor is a kind of chronic consumptive disease, which leads to malnutrition, so the patients will have weakness, emaciation and other manifestations, tumor markers and other tests can assist in clear diagnosis. There are many reasons why people in their 70s may have no energy, so it is recommended to consult the doctor in time to avoid delaying the condition.