First things first: make sure to get a warm-up in! This is an important step to get your body ready for the journey ahead. According to the Mayo Clinic, warming up gets your cardiovascular system ready to work hard and may also reduce the risk of muscle soreness and injury. A warm-up may cause mild sweating, but it shouldn't leave you fatigued. The Mayo Clinic recommends a warm-up that includes leg stretches and walking briskly for 5 to 10 minutes. When you start your run, remember to ease into it — start by jogging slowly and increase your speed gradually.