running with weights

I've been doing CrossFit for 2 years... there are a few workouts that we use a weighted vest... believe me wearing a vest definitely alters the difficulty of accomplishing the work and therein provides more power output and impacts cardo gains from a workout without the vest.

In regard to it's benefit to a strict runner, of course there would be a statistical benefit to fitness wearing the vest versus not, but to better your running performance I'm not sure that would be a beneficial investment.

I would first look at your workout itself and consider some variance in your routine. If your consistently running a certain distance, lets say 2 miles per workout... up that to three... Becoming proficient at a 3 mile run will enhance your 2 mile performance.

Also consider going short... running springs, and sets of sprints... 100m sprint, rest for 30 secs, 100m sprint, rest for 30 sec, etc, etc... Just some thoughts... hope they are helpful.