Drivers need to take breaks and exercise every once in a while. On a lunch break, job around the parking lot of a truck stop, or do some sit-ups, pull-ups, and push-ups Rocky Balboa style underneath the trailer.
For sit-ups, place the back of your legs on top of the cross bar that connects between both landing gears under the trailer for allowing for max flex intensity of a sit-up.
For the pull-ups, lay under the trailer as if you were road kill and grab the cross bar with one or both hands and try pulling yourself up straight without bending at your back.
For push-ups, lay on stomach, and place both feet over the cross bar, keep your legs and back straight and go to it.
Not all trailers have that cross bar under the trailer that connects to the frame of the trailer, between the landing gear. So if that ever happen, just save the exercise when you do have it. That cross bar is strong and sturdy it will tolerate thousands of pounds. So there isn't any excuse that drivers can offer.
It is important for drivers to stay in shape, or otherwise drivers will increase the risk of other health issues.