Next time your friends brag about their last workout ask them how much rest they took! Learn more about rest intervals:
But, what if you want to work on running faster (mechanics, speed, form, and efficiency) without sacrificing the long-term goal of progressing aerobic development? The answer is easy: You can add short rest intervals to break up your tempo runs to run faster or go longer. Inserting short rest periods will allow you to run faster than a tempo pace (usually 6-7 percent faster, or right around 10K pace), but because the rest is short, you can maintain a threshold effort for the faster portions of the workout. My recommendation is to break up these runs into half mile or mile repeats and take between 30 and 60 seconds rest between intervals, depending on your ability level.