@TwinDogsDifferentMothers:
The load or "walk in the park" depends on the pace and the terrain. We do not walk on a garden path. Its hilly and uneven. We actually walk our dogs for exercise for them and us and its not a leisurely stroll. We also do not have Canadian weather so there a great change that our conditions will be different. Just curious, do you get with your dogs for several miles daily? We do!
Depending on whatever has to be done around here, if there is time I often take Perry to the regional forest, which is extremely hilly and 200 acres of criss crossed trails. My average walking pace, according to the tread mill at the gym, is 3.8 m.p.h., which I find comfortable. If I am in a hurry, I can push it up to a bit over 4 m.p.h. beyond which we are jogging. (which I don't do much any more since my knees get sore), I don't do the forest as much as I used to because I spent one whole summer with poison ivy rash on my legs, and got tired of it! 
Here is Perry in the forest…
When I don't have time for an extended hike, we go out around the hayfield, generally at least three times a day. I walk the perimeter…...about half a mile......and he runs loose, so he does a lot more mileage than I. Here he is in the field (1st pic taken from a video hence the poor quality)
Of course he pants when he runs, and as I have mentioned, he is less heat tolerant than my previous Basenjis. The panting stops when we take a break (in the forest. The field walks are not long enough to need one) In Ontario, the weather is quite variable, but in summer we can have oppressive heat and humidity, often for days at a time. Yeah, I know, it isn't Texas. 
(I'm curious, though. Is Texas dry like Arizona, or humid?)
Back in the day, with my first Basenji, I used to take her with my horse for trail rides, which would inevitably involve some galloping, as well as a minimum 5 miles of roadwork, walk and trot. Yes, she would pant! But stop as soon as we pulled up for a rest. I was young and thoughtless and never carried water (if wasn't the norm back then) and had no difficulties with her and the heat at any time, including 90 F + days, but she was a tough girl and perhaps they generally were 40 years ago. Here she is at the farm:
My second Basenji was also very heat tolerant and could handle cold as well. We used to go cross country skiing on the lake with no coat or boots to keep her warm. Once she chased a skidoo for over 3 miles before she gave it up! But that was obviously in winter. In summer she would jump off the dock and chase water skiiers. But now I am off topic. Here is Lady in the snow at 10 F.
As you can see from the pictures, the dogs described were running loose, and therefore getting a lot more exercise than I was!
