You don’t have to perform rigorous exercises in the heat in order to benefit from them. Walking is a great way to prevent swelling because it gives you enough cardio to get your blood flowing. This consistent blood flow is what will prevent your body from swelling. 30 minutes of walking daily is a good amount to start with to avoid swelling.  If you already exercise regularly, keep doing what you’re doing. Consistency will be key in keeping your body regular. If you have to be somewhere for a long amount of time, make sure you’re getting up and moving. Avoid sitting or standing still for long periods of time because it will lead to swelling in your feet. Avoid cotton clothes in the heat. Cotton retains moisture and will only make you hotter. Wear tights or circulation sleeves to help your vessels circulate properly.  Look for clothing labeled with Celliant fibers. Reebok, Adidas, and Saucony are popular brands that use this a lot. It is a fiber that redirects recycled energy back into the body, increasing blood flow and blood oxygen levels.  For a more professional look, you can buy circulation tights that boost blood flow. For men, you can get circulation sleeves that fit over your arms and wear these under your shirt. If at all possible, stay inside during the day—especially in the afternoon. The afternoon is typically the hottest time of the day, and depending on where you live, if may not cool down in the evening. Do your outdoor activities during the morning.

How would you rephrase that briefly using Vietnamese?
Năng vận động. Mặc quần áo kích thích lưu thông máu. Ở trong nhà.