The National Automotive Sampling System Crashworthiness Database System (NASS-CDS) contains cases of severe injury side-impact collisions despite the normal activation of occupant restraint devices. A likely cause is that an occupant was out of the intended protection area of the side airbag. In this study, MADYMO analysis was conducted to analyze the effects of a side airbag on an occupant in such a posture. Panelist evaluation was also performed to measure the load and time for a pre-crash seat belt to pull an occupant leaning forward back into the side airbag protection area. A THUMS version 5 was used to determine the effects of muscle activity on occupant’s pullback time to eliminate individual differences between the panelists. The THUMS was controlled to simulate the behavior of a specific panelist. This study shows that the workload of a pre-crash seat belt is related to the pullback time, inertia and muscle activity required for an occupant to be pulled back to the side airbag protection area.