How do i obtain the ability to sprint super fast on Modern Warfare 2 For Xbox?

When i was playing a free for all match some guy was zooming across the level at unbelievable speed. before i could aim down my sight he had stabbed me and two other guys around me. I've been to forum after forum and everyone keeps talking about how it happened to them but no one can tell me how to get this for myself. I need to know!How do i obtain the ability to sprint super fast on Modern Warfare 2 For Xbox?
HA HA, well what you do is you have Marathon and lightweight on, and get a 4 kill streak for a care package. With the care package you can literally get across the map in under about 10 seconds with the perks marathon and lightweight.

There is also mods that you can get but they are patched now.How do i obtain the ability to sprint super fast on Modern Warfare 2 For Xbox?
Using the perks Marathon and lightweight give you faster running and the ability to sprint nonstop. A Tactical Knife attachment on your sidearm improves your stabbing speed.How do i obtain the ability to sprint super fast on Modern Warfare 2 For Xbox?
There are two perks you can obtain. The first one gives you unlimited sprint and the second increases your run speed. Used together, you can zoom around knifing people before they can get their sights on you. Sorry -- I forgot the perk names but you get them really early on.
Turn on Marathon, Lightweight, and Ninja for your 3 perks. Marathon--unlimited sprint, Lightweight--Run faster, Ninja--silent footsteps. If you have pro, your better off as well. These are easily unlockable during gameplay. Make sure you have the tactical knife attachment for you handgun. Without this, your chances of stabbing are slim. Don't camp, keep running the perimeter. Stay away from all of your teammates, if any. If this still doesn't look like what you saw, then the person used a speed mod, but this would've made everyone in the entire game super fast.