Appreciate your concern barkingdog, Halo is 12 years old and loves going for long walks every day. We walk slowly to accommodate her advancing age, but she is extremely healthy (per my vet last week). My last black dog walked daily until she was pts at 14. Not sure saying she didn't enjoy the walk was fair, she just took it very slowly due to the heat, which was fine with us.
I do believe that the water we poured over her head and down her back and neck helped to cool her some, she seemed okay with it. Not to worry she had lots of water and we were only out for just over half an hour. Most of our walk was in the shade as it is a heavily bushed/forested area, and there were many, many dogs out there with us.