Alright, I have been running on and off for as long as I can remember. I started again 3 or 4 weeks ago and I have built my endurance up sense then, but I still don't have much stamina for bursts of running or sprinting. How do I go about getting to where I can sprint longer and faster? Should I just practice sprinting, or are there effective methods for training this? Advice would be helpful, thank you.