Prospective inception cohort. To assess the prognostic value of spinal mechanical load, assessed with the 24-hour schedule (24HS), in subjects with acute non-specific low back pain (ALBP) and to examine the influence of spinal mechanical load on the course of ALBP. In view of the characteristics of the natural course of ALBP, this should be viewed as a persistent condition in many patients rather that a benign self-limiting disease. Therefore, secondary prevention could be beneficial. Spinal mechanical load is a risk factor for ALBP and possibly a (modifiable) prognostic factor for persistent (i.e. recurrent and/or chronic) LBP. One hundred patients from primary care with ALBP were eligible for inclusion. At 6 months, 88 subjects completed the follow-up. For the follow-up assessment a research assistant, unaware of our interest in the prognostic factors, contacted the subjects by telephone. Questionnaires were completed focusing on changes in demographic data and on the course and current status of ALBP. Persistent LBP occurred in 60% subjects. After multivariate regression analysis smoking (harmful) and advanced age (protective) were associated with persistent LBP. Differences in 24HS scores at baseline and follow-up were univariate-related to persistent LBP. Spinal mechanical load, quantified with the 24HS, is not a prognostic factor for persistent LBP. Modification of spinal mechanical load in terms of 24HS scores could be beneficial for secondary prevention in patients with acute LBP.