Because femoral and other leg muscles are large, engaging your leg muscles in hard anaerobic exercise is the most efficient way to burn your calories and increase your aerobic capacity. Staying lean will help develop speed and use your muscles and lungs more efficiently.
Run uphill 3-4 times a week (make sure you use good running shoes - like Brooks Cascadia and retire them every 800-1000 miles). Trail running will keep your metabolic rate high and will help develop mental and physical endurance. Off season, supplement your trail runs with a variety of upper body exercise, 3-4 times a week. Taper and climb mountains in summer – train in winter. Make sure you eat tons of proteins and recover after your long runs with lots of carbohydrates. The later will block lactate production in your muscles. Drink lots of water. Avoid alcohol and women…just kidding