A couple of thoughts after reading the article Dagny linked. Always carry something to wrap pads in case of injury. Vetwrap with padding and a boot if possible. Also from the article this dog became tired and weak. My guess heat and stress from the situation. Canine rehyration tablets or packets are always a good idea to carry with dogs and I always carry a couple small packs of honey to counter shock. Watch your dog closely and stop before the dog gets into trouble.