Get thee to a gym! Learn to deadlift and/or squat. It's OK if you're not doing it with a lot of weight, though if you push just a little you'll be surprised at how strong you are / can get with time.
Also, it's interesting to work with lighter weight, you can feel how to 'redistribute' it through bending at the waist (WITH STRAIGHT BACK) to lift with the glutes or more with the knees to put the weight on your legs.
I use gloves and a back brace when I'm lifting in the gym, but if I'm pulling 400lb off the deck there, 250 at work isn't too hard.
Though it can be a little uncomfortable working with fatigued muscles the next day