It says for the challenges for the perks lightweight & Marathon that for marathon run X miles & lightweight sprint X miles, i personally think Infinity wards got it mixed up and was suppose to be the other way around since marathon makes you have unlimited spring and lightweight makes you move faster. Is run what you normally do when going are walking around the maps and sprint is when you burst into running for a short amount for time, unless you have marathon on?
If not then what is the difference between the two in the game?