With the duties and responsibilities of the military, they are on the cutting edge of R&D and the latest and greatest technologies. One significant problem effecting thousands of soldiers are injuries to the lower limbs, specifically the knees, as a result of high impact to the joints and muscles. Through the research of biomechanics and ergonomics during human locomotion of running, cause and effects fatigue, muscular activation during running, gait cycle force analysis, and biomimicry of kangaroos, we were able to identify lower limb exoskeletons as a viable solution to the problem. The purpose of this research was to develop a relatively inexpensive prototype of a passive lower limb exoskeleton to aid in injury mitigation and muscular efficiency for soldiers. The hypothesis was that a lower limb exoskeleton would reduce/mitigate injuries by reducing stride length and increases stride frequency to lower impact on the knees while running. The prototype was tested by one participant on a 2-mile course with two load variations tested while running. The key results were seen from the spring systems potential to increase average stride cadence/frequency by 6–14% and reduce impact on joints and muscles by increasing the number of steps and reducing high center of gravity oscillation by 13–27%. Furthermore, this study provides evidence and research that proves that a passive lower limb exoskeleton design, which increases stride frequency and reduces stride length, can mitigate injuries to the lower limbs when running with weight by reducing the impact forces on the knees and improving running economy.