###Human: What causes decreased heart rate while lying down? ###Assistant: Hi. Your heart rate is normal and this variation in heart rate during exercise and rest shows a healthy heart. Just keep your heart healthy for the rest of life by moderate exercise, avoid alcohol and tobacco, avoid stress and fatty meals. By following these measures you can enjoy a healthy life even in your 80s. This perfect healthy happy heart is a precious gift. Please protect your heart as heart will protect you too.