Lab X - chewing and exercise

Question
Good evening Labman!  I'm glad I found you :)  I have a 6month old lab mix puppy.  We crate him at bedtime and he gets the kitchen (with a baby gate) during the day while we are gone to work.  He has been great until just this week.  He chewed a hole in our wall - i have tried the bitter spray and also tabasco sauce to keep him from chewing things that he isn't suppose to, but he LOVES both of the tastes.  It appears that our puppy will eat everything :)  I was just wondering - some people say that he is just bored, some people say he may be having separation anxiety.  If he is bored, should i exercise him for about 1hour (walking?) before i leave in the morning for work?  

This then goes along with my next question of how much exercise is too much for a 6month old puppy.  We have taken him on short hikes with us on the weekend (about 1-2 miles).  A 30-45min. walk does not seem sufficient any more.  We would like him to go mountain biking with us when he gets older and stops growing - we have taken him out a few times to get him used to staying away from the front tire.  I'd hate to run him over....there are a few times that he has "Chased" down my boyfriend at full speed.  

Lots of people say too much exercise is bad, but what does that really mean?

Thank you so much!

Answer
I would crate him in the day time too.  It would be better if somebody could make it home to give him a mid day break.  If you can't see if a neighbor or a professional dog walker could.  If you can afford it and it is available, doggy day care is always great.

Long walks shouldn't hurt a 6 months old.  The more, the better.  Avoid much running and jumping until after he is a year old.  Think low impact exercises.  Keep him lean and switch to an adult chow now if still on puppy chow.  To judge his weight, see  http://www.longliveyourdog.com/twoplus/RateYourDog.aspx