Cornbread
I rode hundreds of miles with my Vizlsa's through the years on a Mtn Bike, So I'll try to give you my insight.
All of my dogs could "eventually" run for hours with me, and I can state that my pace on a MTN Bike would not be considered slow by any means (Former USCF Bicycle racer).
The considerations that have to be given for a dog are the same as a human. They're subject to the same conditions a human athlete is with repect to blood volume, lactic acid and ATP cycles, etc. The aerobic and cardiovascular systems must be developed over time. Additionally all of the soft joint tissues and joints have to be strong enough, and developed enough to support the load. The nutritional requirements to run my dogs at that level was beyond simplie dog food. They ate a supplemented diet of rice, lean meat, chicken, fish oil, and I carried electrolyte replacement fluid for them, instead of relying solely on water alone. The were given supplements of Glucosamine Sulfate and Chondroiton and also supplemeted with B-Vitamin stress tabs.
6 months is too young in my opinion,and while my dogs were out with me at this age, they were fun runs to and from water, playing, etc. Never very far from either water or the truck. His joints, cartlige,and connective soft tissue still need to develop, or you may risk the onset of arthritis earlier in his life than may be normal.
If I were to ride a MTN bike for 20 minutes at speed I would easily travel close to 8 miles on a flat road. A dog zig zagging around to and fro could easily cover twice that. That's a lot of miles for a dog, and yes, a Vizsla's desire to please his owner can easily lead to them pushing themselves beyond the point of simple exhaustion.
Every year hunting dogs of all breeds succumb to heat exhaustion and cardiac arrest, by being pushed beyond their current fitness level during hunting season. It happens. :'(
I'm not trying to be an alarmist here, or scare you. My best memories of all my dogs have been the hours we spent training in the forest and just messing about. Give your guy time to grow, develop his strength, and his cardiovascular system, and you'll be setting yourself up for some incredible good times, and great memories. Keep a camera at the ready, and make sure to carry some extra water bottles for him so he always has access to clean water( I used Cytomax).
