Just got a new job and they incentivize running to work. It also saves me a lot of time since I usually run doubles anyway. I've got a small "ultra running backpack" that feels fine to run with so I can carry lunch/clothes. Probably an extra six pounds or so.
Do you think it would be undesirable to incorporate this into training almost every day? It's only about four miles away, so I could use it as a warm up for evening workouts and then run the workouts sans-backpack.
I have noticed my calves get a bit fatigued with the backpack, even though the effort level is very low.