To help with endurance remember to take little steps and pull up your knees. Dont push with your calves. By taking little steps and lifting with your thighs you are using less energy and can get more endurance out of your run. This also helps with hills. By doing this you will pull yourself up the hill, instead of pushing up the hill. Less tendon, ankle and calf pain. Plus after doing this 123 mantra every now and then in your run, you will gain muscle memory. This will become automatic, and you will increase your speed and time by using quick little steps, and burn less energy.