Take a 5-7 minute walk, first thing, to warm up your muscles and elevate your heart rate. Gradual warm-up (5 to 7 minutes) is important to elevate your heart rate prior to the more vigorous portion of your walk. Then stretch. Stretching warm muscles prior to your fitness walk will help you avoid injury and stiffness. Hold the stretch for 20 to 30 seconds, feeling a gentle pull - do not bounce. Make the vigorous part of your walk last a minimum of 20 minutes. Keep your arms pumping to help keep your heart rate up. Your cool-down should be gradual, with 5 or so minutes of easy walking. Moving at an easy and relaxed pace allows the heart rate to return to (or near) a resting heart rate. Follow up with a post-walk stretch. You can use the same stretches you did during your warm-up.