Dogs put the majority of their body's weight on their "hands" or front legs. They tend to be more "front loaded" or "front wheel drive" as we've discussed before and in our exercise e-book.
The majority of their activities ALSO encourage this "front" posturing (similar to what we do at our desks, computer, watching TV, driving) so they end up with stronger muscles than in their back legs.
Problem is, most of the debilitating and costly injuries (in terms of pain and finances) tend to be in the back -think hips and knees.
A carefully curated program of exercises will help tremendously much like the elevated standing exercise he's doing in the above pic.
Always use a chest harness
Use pieces of their regular food instead of treats or cookies
Little things go a long way!