It's a blue collar job. Get over it. You think UPS drivers have the most laborious job out there? There are countless jobs with long hours, high risk of injury or death, and heavy workload on the body. If you workout outside of work to remedy muscle imbalances, eat a decent diet, sleep, and work on flexibility, you will be able to stay in any job longer.
As stated above, a desk job is worse on your body than a job where you are on your feet all day. I can honestly say I feel sorry for the limp wristed, upper cross syndrome suffering pencil pushers I see when I deliver to offices. I'll bet they end up with back issues before I do.