So it is potentially a question of intensity. It is not just doing things, moving the body, physical activity. More important is focussed intentional activity that improves fitness. Proper exercise if you like. Don't just move...get fit.
Physical fitness, rather than self-reported physical activities, is more strongly associated with low back pain: evidence from a working population.
These findings suggest that physical activity of an intensity that improves physical fitness may be important in the prevention of LBP.