If your dog is very active, he may need longer, more vigorous walks, perhaps even two or more times a day. (pedigree.com)
The Old English Sheepdog isn't the most high maintenance of dogs in terms of formal activity and exercise; it needs about an hour a day of vigorous walking in two or three sessions. (mypetneedsthat.com)
Determined to start labour naturally, I got up the morning before my scheduled date and went for a long vigorous walk. (health-and-parenting.com)