Knowledge Bank

BACKGROUND: Exoskeletons for military and civilian tactical athletes are potentially beneficial tools to increase survivability and enhance operational capabilities, but are largely designed from basic movements, such as normal walking. In order to provide exoskeleton developers with the most comprehensive information to design these devices and mitigate restriction of the user’s abilities to execute occupational duties, it is warranted that tactical walking movement patterns be investigated. METHODS: Twenty-four male tactical athletes (22 active duty Army Soldiers, 2 civilian SWAT operators; age: 23.83 ± 5.47 years; height: 1.80 ± 0.08 m; weight: 81.04 ± 7.87 kg) participated. Tactical athletes performed normal walking and tactical walking (i.e. walking while maintaining weapon aim or ‘shoot on the move’ [SM]) along a 15-meter path. Both tasks were completed under three speed conditions: (1) self-selected slow speed, (2) 1.12 m/s , and (3) self-selected fast speed. Three trials were completed for each speed and speeds were completed from slowest to fastest. Lower extremity kinematics were collected via wireless inertial measurement units (myoMotion, Noraxon ISA, Inc., Scottsdale, AZ). Spatiotemporal parameters were collected via optical detection system (OptoGait, Microgate, Mahopac, NY). Repeated measures 2 (walking task) x 3 (speed) ANOVAs were performed for dependent variables. Tukey HSD post hoc pairwise comparisons were performed for significant effects. Alpha level was set a priori at p ≤ .10. RESULTS: Main effects of walking task and speed condition were observed on lower extremity kinematics where tactical athletes exhibited larger flexion angles during SM than during normal walking (p < .01) and larger flexion angles during faster speeds compared to slower speeds (p < .01). Longer strides and less time spent in double limb support were observed during faster speeds compared to slower speeds (p < .01). A walking task main effect was observed on stride length were tactical athletes adopted shorter strides during SM than normal walking (p < .01). CONCLUSION: Military and law enforcement personnel exhibit different movement patterns during tactical walking compared to normal walking. These modified gait patterns are also influenced by speed of movement. These tactical athletes perform occupationally-relevant movements and tasks that may not directly translate to basic movements. Therefore, it is critical that information on these occupationally-relevant movements be accessible to exoskeleton designers to build optimum control systems that will aid and not hinder tactical athletes in their roles to serve and protect. Outside of tactical populations, exoskeletons for rehabilitation applications would potentially benefit from understanding biomechanics of more complex movements to design more robust control systems when used for general populations post-injury, such as spinal cord injuries or stroke patients. Findings from our study highlight fundamental differences between basic and complex movements which translate across multiple domains to enhance human performance.