Question: Our puppy (8 months old, Husky/Shepherd mix) is getting to be good enough on the leash that I can take him for a nice run. I live near a park with a 5K loop road, which I used to run regularly. 

When I first started taking him out around the loop road, he'd jump at me and bite and try to get me to play right away, or at least at fairly arbitrary intervals. I got a good lesson in dominant walking, and a better slip lead that actually loosens again after I tug it so I can keep it high on his neck, give it a quick tug and re-orient him to following me and we can keep going. That had a huge impact--he's way, way more manageable. My pace is pretty slow, he seems to handle it very comfortably, and we stop for water. 

But since the walking lesson I've noticed that about 2/3 to 3/4 of the way through, he still gets really unmanageable. He tries to jump on me and bite playfully, but he forgets his bite inhibition entirely. The other day he did this really manic digging for a few minutes. Just scraping at the soil with dirt flying and shaking his head and jumping around. In general, it seems like he just gets manic and bonkers, jumping around and barking at me.

It occurred to me (this might be obvious to everyone else?) that 5K might just be too long for him to run. Do I need to find a shorter route, or is there something else going on?

P.S. There's a mention of overtiredness at [What can I do if my puppy is hyperactive?](https://pets.stackexchange.com/questions/141/what-can-i-do-if-my-puppy-is-hyperactive?lq=1) which seems to suggest that's exactly what is going on. But I'd love to know more about how to tell when a young dog is getting overtired.

Answer: 
There's not enough information in your post to provide a valid clinical picture. All of the behaviors you mentioned are *natural dog behaviors* that can occur in many situations.

Context Matters
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Consider that digging can be self-rewarding play or prey drive, or it may be stress-displacement behavior. "Jumping around" in a bouncy way is generally a play behavior, but would generally be paired with play bows and other cues if it were all in fun. "Barking" has [a whole range of meanings](http://www.psychologytoday.com/blog/canine-corner/201103/what-are-dogs-trying-say-when-they-bark), but rapid bursts of barking with bouncy body language is most likely excitement or attention-seeking behavior.

"Just the Facts, Ma'am"
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Focus on the facts:

1. *Your dog loses interest in the walk (or gains an interest in something else) after a given distance or time interval.*

Experiment. Try shorter distances or time intervals. Try avoiding specific areas that trigger arousal. Learn more about dog body language, and respect your dog's signals that he's tired, bored, or over-stimulated.
2. *Your dog loses bite inhibition when aroused.*

Avoid situations that cause excessive arousal. Learn to read the signals that your dog is becoming aroused before he hits DefCon 1. You might also train an alternate behavior (like a down-stay) that is designed to reduce arousal.

By focusing on observable behavior, rather than trying to guess about your dog's internal processes, you can avoid or manage almost any behavior. Your dog is clearly trying to communicate with you; however, learning *what* he's trying to communicate will require time, effort, and research on your part.
Young dog is very curious about the world surrounding him and if you take him for a walk and force him to walk besides you like a walking robot and not having a chance to examine the world around him - he won't be very happy with that.

You should allow him to sniff around, to take a better look into various details he finds interesting, wait patiently while he examines smells and markings from other dogs and animals etc... This is very important to him.

Not allowing the dog to do his "doggy things" is like taking a child into a kid's playground and expecting him to sit quietly on the bench.
Be aware that the smell is the dominant sense in dogs, way more important then the sight, and the dog that doesn't get his chance to sniff around is like a man who goes for a walk with his eyes covered.

Remember, when you're spending time with your dog try to do things that pleases him too, not only you.

The reason why your dog starts doing "weird" things near the end of your walk is probably that - as the walk approaches it's end - he realizes the time is almost up and he won't get any of that he hoped for, and then he tries to do something about that at the very last moment.

Let him go for the first half of walk his way, and end up the rest of the walk your way.
He'll be very grateful to you.

And yes - huskies like to dig.
Leave him a few days in your backyard and he'll make you a beautiful large scale model of Moon's surface on your lawn yard.