The study was conducted in the Netherlands and asked a population of police officers about their activity levels and episodes of low back pain over the preceding 12 months. In addition to questioning, their levels of physical fitness were actually measured objectively (hence minimising the problem that often arises with this sort of study where people inaccurately record their activity levels, often tending to over-report). Results were collected from nearly 2000 individuals and the findings were conclusive - moderate levels of physical fitness (both muscular and aerobic) correlated with a lower incidence of low back pain, whereas the occurrence of low back pain increased with lower levels of activity and physical fitness. So, the implications of this are clear - exercise regularly, improve your fitness levels and you should experience fewer episodes of low back pain!
However, it is not quite that simple - it may be that people refrained from exercise due to their low back pain, hence their back pain worsened, hence they exercised less - something of a Catch22 situation! Additionally, the findings showed that excessive levels of exercise actually increased the episodes of low back pain - this was particularly true of highly strenuous, vigorous activities such as weight lifting or heavy gardening and was a problem that mainly affected the male cohort of the study.
In conclusion, this study showed that physical activity, strenuous enough to improve physical fitness, was strongly associated with lower levels of low back pain. So, the message is clear - get moving, get fit and you should have less low back pain (but take it gently and sensibly as excessive exercise might cause more harm than good!).