For occupations such as fire fighting, the back brace would not be logistically convenient or biomechanically efficient simply by the nature of the unpredictable work environment.  The most prudent idea to truly protect this special population would be a comprehensive hips and trunk stabilization and conditioning program.  Many programs are targeted toward a healthy back when the coordination of the hips and trunk should be the ultimate focus.  This is not to say that a weight belt should never be used, but rather considered more of a last resort where the appropriateness is carefully scrutinized.
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