I recently adopted a year old puppy and out of desperation to deplete her boundless energy, I started taking her on my morning runs and just my luck, she loves it. I started slow, a mile round the block at first and have built up to about 4 miles. She seems to have reached her limit here. So my question is, should I limit my runs with her to 4 miles since this seems to be her physical limit? Or, like humans, is this something she can train through.
Specifics on the pup (she's a pound pup so some is speculation): bout a year old, approx 30 lbs, short hair, best guess is a border collie/terrier mix, gets water before, halfway, and after run, use body harness and leash. We've done a couple 5ks together (very successful) and were working for her first 10k until this delima
Canine endurance is much different than humans. I would not push it any further. Just like people, canines exercise limitations vary. However, canines, no matter what the breed, can get heat exhaustion fairly quickly and can die from it. Many factors such as climate, humidity, heat, time of day, age, diet all play a factor.
I am an emergency vet tech and we treat heat exhaustion in animals frequently. Sometimes they can recover if caught early enough but sometimes their metabolic processes begin to shut down because they can't keep up. I would recommend running with your furry friend in shorter distances, nothing more than 5k's. As you mentioned, providing water throughout is important. Also canines age faster than we do. Therefore, arthritis deveops much faster.
Meanwhile, have fun with your dog while you can and continue to keep an eye on your canine friend. Become familiar with normal/abnormal behavior. They have good days and bad days too just like us. They develop muscle strains and get cramps just like we do. Do not hesitate to call your vet if you have any questions.
I very much doubt that fido has reached her physical - as in muscular, or energetic - limits. The issue is - and CJMark hinted at that - that dogs have a different temperature regulation systems than humans. While we sweat as a way to cool and are therefore able to consistently exercise for long periods of time, dogs don't. Their only way to cool is through their tongue and simply taking breaks. I would therefore try to do intervals and see how she responds to that, or take her to a track workout and provide her with a place to rest (and show her that is it ok to do so, too) while you keep running.