Re: How soon can I start running with my vizsla?
It's really up to the dog.
You have to watch them and give them periodic rest intervals and free access to water.
When I would take my dogs Mtn. Biking in the forrest, I always tried to swing by the ponds, creeks and streams every 15-20 minutes or so, or I would stop and let them drink from a water bottle. (If you are going to run trails with your dog, it's absolutely essential that they learn to drink from a water bottle.)
In all honesty though, short of getting ready for the Olympic 10K, or Rotterdam, no Vizlsa will need much of a "build up period. You just can't run fast enough. Keep them off Asphalt and concrete, Don't do any boulder scrambles and they'll come right up to your level very quickly.
They do need their rest interval though. If you run them 2 days, give 'em a day off with good food. Same as hunting one.
The quickest way to get these dogs off the leash and checkcord, is to get them physically and mentally engaged with you.
MIne probably started at about 6-8 months, but were out and about at their own pace level as soon as they came to me.
You'll never beat a lesson into a dog, you just beat desire out.