METHODS This study analyzed improvements in cardiovascular fitness and muscular strength after a 6-week work hardening program. OBJECTIVE The objective of this study was to document fitness gains after a 6-week work hardening program. BACKGROUND Studies expounded on the success of a functional restoration approach in return-to-work rates, but few documented the physical fitness gains of a work hardening program. METHODS Thirty-one subjects from the Rehability Center in Lubbock, Texas, who were diagnosed with lower back dysfunction, completed the 6-week study. A submaximal cycle ergometer protocol was used to determine patients' cardiovascular fitness levels, and the Arcon Static Strength Testing Device was used to measure static strength. Pre- and post-tests were identical. RESULTS A paired Student's t test was used to analyze the significance of difference from pre- to post-testing. For cardiovascular fitness there was a 28% improvement, t(29) = 5.56, P < 0.001; there was a 76% improvement for the static arm lift, t(29) = 7.86, P < 0.001; there was a 57% improvement in the static pull, t(29) = 9.53, P < 0.001; and an 89% improvement in the static push, t(29) = 9.08, P < 0.001. CONCLUSIONS Analyzed data clearly show a marked improvement in cardiovascular and muscular fitness. There was not a difference in fitness levels between those who returned to work and those who did not, which suggests return-to-work rates are not entirely based on level of fitness.