Exercise with a Golden R.

Question
I have a 14 month old Golden and he is great in every aspect a dog can be.  The question I have is I work ten hour days five days a week. I get up very early and get home and usually too busy catching up on things around the house to go running with him.  Although on my days off we go to the lake and he loves to run, swim, chase ducks and balls and is relaxed for days after.  I can see lately during the week he is getting some behavior problems and I heard that was due to lack of exercise, first is this true and second, what can i do if anything to substitute running him till he is tiered?  And finally what is a great toy to give him exercise to play with when I'm not home?   Thank you

Answer
I don't have a good answer to your problem.  Perhaps you could hire a professional dog walker to give him a mid day walk every day.  Another solution would be to put him in doggy day care.  If not every day, perhaps Tuesdays and Thursdays giving him a couple of breaks a day.