Sarah Lanham: The Acute Effect Of On-duty Endurance Exercise on Neuromuscular Function And Working Memory In Structural Firefighters

Abstract Purpose & Aims: Overexertion induced musculoskeletal injuries and sudden cardiac events are significant threats to firefighter safety and health. Cardiorespiratory endurance is associated with risk of musculoskeletal injury and cardiovascular disease. Thus, firefighters must possess adequate cardiorespiratory levels to reduce these risks and high intensity interval training (HIIT) and long slow distance (LSD) are effective types of endurance training. The National Fire Protection Association recommends that firefighters perform on-duty exercise to enhance firefighter safety and health. However, on-duty exercise is often interrupted with emergency calls, thus requiring firefighters to perform rigorous occupational tasks and retain critical operational information in a fatigued state. Fatigue, or overexertion, is the leading cause of fireground injuries, followed by slip, trip, fall mechanisms. Furthermore, fatigue has been associated with reduced working memory function. Thus, it is critical to elucidate the impact of on-duty exercise on subsequent risk of injury and working memory. Therefore, the primary aim of this investigation is to evaluate the acute effect of LSD and HIIT exercise on neuromuscular function and working memory in structural firefighters. The secondary aim is to identify fitness- based characteristics that are associated with decrements in neuromuscular function and working memory. Relevance: Performing regular on-duty exercise is critical to enhance occupational readiness and safety across the career span. These findings will guide the development of appropriate on-duty exercise recommendations to reduce the risk of exercise-induced overexertion and slip, trip, and fall injuries and maintain working memory while performing occupational tasks. Methods: A convenience sample of firefighters (N = 20) will be recruited to complete a battery of fitness assessments. Specifically, a graded exercise test will be used to measure ventilatory threshold, aerobic capacity (VO2max), and identify the heart rate corresponding to 77% of VO2max to be used in the LSD exercise session. Muscular strength will be assessed with an isometric midthigh pull, whereas muscular power will be measured with a vertical jump. Muscle endurance will be assessed with a push-up test. The 30-15 Intermittent Fitness Test (IFT) will be performed to establish the HIIT session intensity at 90% of maximal aerobic velocity. Neuromuscular function will be assessed prior to and 10 min post endurance exercise in personal protective equipment using force plate assessments of postural sway, single leg landing, isometric midthigh pull, and functional balance test outcomes. Similarly, working memory will be assessed using a set of occupationally relevant radio communications where firefighters will be asked to recall critical operational details. Mixed factor (exercise condition x time) ANOVA will be used to assess differences in dependent variables within and between conditions across time points. Post hoc analysis will be conducted using paired sample t-tests. Effect sizes will be assessed using partial eta squared. The level of significance will be set at p < 0.05 and Bonferroni adjustment will be applied where appropriate. Minimal difference analysis (ICC Method) will be utilized to assess individual firefighter responses to the exercise stimuli. Linear regression analysis will be used to identify the strongest predictors of decrements in neuromuscular and executive function. Anticipated Outcomes: We will describe the impact that on-duty HIIT and LSD training have on neuromuscular function and working memory in firefighters. Furthermore, we will identify predictors of the residual decrements in neuromuscular function and work memory in occupationally relevant assessments.