This book intends to ascertain WCA's predictive validity for low back pain in workers in the sustained labor category. Task analysis was performed for all the activities and classified under risk zones and graded accordingly for the occupations carpentry, painting, plumbing, electrical work, housekeeping, and janitors. The results have shown to have a significant degree of association with low back pain falling under (0.6- 0.8 moderate association). Work capacity assessment has a moderate association with low back pain. The tool of work capacity assessment needs to be modified to have clear instructions wherever it is ambiguous.