Since a patient's ability to perform simulated work activities guides return-to-work decisions, a significant question to address is whether the simulated work environment accurately reflects the actual work environment. Work hardening programs have been used extensively as a method of rehabilitating workers to return to their pre-injury functioning levels. Re-training workers to lift boxes is a common method used to simulate the work environment. Although very few boxes used in the real work environment have handles, boxes with handles are often used in the simulated work environment. The difference in compression forces at the L5/S1 joint while lifting boxes with and without handles was investigated. The Lift Trak Motion Analysis system was used to estimate lumbar isometric compression forces exerted while lifting a 20-pound (9.07-kg) box. The results indicated that estimates of compression forces when lifting a box without handles were significantly different (p < 0.01) than when lifting the same box with handles. Based on these results, it is recommended that work hardening professionals carefully re-evaluate the simulated work environments currently being used for treatment.