My re-enacting group uses 1796 Light cavalry sabres. These are replicas and weight about 2.6 pounds, and it's fairly badly balanced. Yet, even on foot it's with relative ease the sabre can be used for feinting, swinging and stabbing, and you have to remember that in mounted combat the speed and weight of your horse adds to that ease (And as light cav, you are supposed to swing a lot). Even I, whose not that strong, can handle it. And then you have to remember these men practiced hours a day.
Infantry officers used straight epees or expensive, well-balanced light sabres. I once held an original epee from a Batavian officer, and it's almost as if the blade's made of air.