A Cochrane review (abstract , review ) included 25 studies with a total of 4 404 subjects. In 14 studies, physical conditioning programs were compared to usual care. In workers with acute back pain, there was no effect on sickness absence. For workers with subacute back pain, there were conflicting results, but subgroup analysis showed a positive effect of interventions with workplace involvement and may have reduced sickness absence duration at 12 months follow-up (3 studies with 283 workers; SMD -0.42, 95% CI -0.65 to -0.18). For chronic back pain, physical conditioning as part of integrated care management in addition to usual care may have reduced sickness absence days compared to usual care at 12 months follow-up (1 study, 134 workers; SMD -4.42, 95% CI -5.06 to -3.79). Intense physical conditioning probably reduced sickness absence duration only slightly compared with usual care at 12 months follow-up (5 studies, 1093 workers; SMD -0.23, 95% CI -0.42 to -0.03).
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment), by inconsistency (heterogeneity in interventions and outcomes), and by imprecise results (limited study size for each comparison).