Combined Effects Of Load Carriage And Tactical Anaerobic Sprints On Executive Function

Load carriage is an essential military task. Research shows that increasing load often impairs cognition. Yet, most of this work has focused on cognitive changes during and post aerobic exercise, or long bouts of fixed-pace load carriage. The modern battlefield is anaerobic in nature, requiring short, quick tactical movements. Adjacent work has shown that acute high intensity interval training (HIIT), or alternating short durations of high-intensity exercise with brief recovery periods, leads to subsequent improvements in executive function (EF) (i.e. inhibition, flexibility and working memory). However, the combined effects of load and acute HIIT on EF remains unexplored. PURPOSE: Examine effects of load carriage and short duration high-intensity sprints on executive function. METHODS: 32 active duty Soldiers (Age: 22.9 ± 3.2 yrs; 32 males), completed a tactical stress marksmanship assessment (TSMA) course under Unloaded (0 kg) and Loaded (~30 kg) conditions on separate days in counterbalanced order. TSMA course included 6 x 35-meter max effort sprints separated by 10 s rest, where targets were engaged. Heart rate (HR) was measured during and perceived exertion (RPE) was measured pre and post-course. EF was assessed at Baseline (~4 wk prior) and post-course using Flanker, Task-Switching and N-Back tasks. RESULTS: Paired samples t-test’s showed that HR was higher during and RPE was higher after Loaded vs. Unloaded (ps < .01). Repeated measures ANOVA’s showed main effects of Load for Flanker reaction time (RT) and accuracy (ps < .05). Planned comparisons revealed that RT on incongruent trials was faster after Loaded and Unloaded conditions vs. Baseline (ps < .05). However, incongruent accuracy only improved following Unloaded vs. Loaded and Baseline (ps < .05). We found no differences between conditions for Task-Switching or N-Back. CONCLUSIONS: The combined physical stress experienced in tactical settings impacts cognition differently than load carriage or HIIT exercise alone. Specifically, improvement in EF (e.g. inhibition accuracy) following tactical sprints is negated when combined with heavy load. Soldiers must maintain EF during various loaded tasks, so quantifying cognitive changes in operationally-relevant load carriage scenarios is critical. Supported by the U.S. Army DEVCOM Soldier Center.