bitch in season & heart problems

Question
Hi, have read a few of the questions submitted as regards bitch danes in heat and need to check a few things

1. bleeding stage is followed by receptive to mate stage?
2. have heard a bit about not running one's danes too hard as they have hearts that are small in relation to their body size - seems a bit of a disadvantage when they were bred to chase boar. When I run my 12 month blue dane - playing fetch for an hour - she does salivate thickly and fairly quickly and I while I would like to increase her stamina I obviously don't want to overdo it.
3.Post run watering; should one wait ten minutes after exertion to allow them to drink or am i just going to the dark side of dane ownership? Gastric torsion is what I am concerned with

Much thanks

Answer
1 Bitches are usually receptive from 10 to 14 days into the season.  A good book on breeding is 'Dogs and how to breed them' by Hilary Harmer.

2 News to me.  A poodle can be trained to run a marathon.  We have owners who run 10 miles a day and take their dogs with them.  The exercise helps to strengthen the heart muscles.

3 A quick sip is OK but too much can make them sick so let them cool down a bit first, just like horses.