Effects of Workload in Novice Military Transport Flights on Autonomic Modulation and Cognitive Performance: An Observational Cross-Sectional Study

Introduction: Introduction: Flight-related stress influences pilots’ health and performance. Research investigating the influence of workload during military flights on those outcomes is warranted. Objective: This study investigated the effects of perceived workload during military transport flights on autonomic modulation and cognitive performance in novice Brazilian Air Force pilots. Methods: In this cross-sectional observational study with 15 pilots. Perceived workload was assessed using the NASA-TLX inventory. Autonomic modulation during the flights was evaluated by heart rate variability. Cognitive performance pre- vs. post-flights was compared using the Stroop color-word test. Results: The perceived workload during flights was moderate (~5 points), with a 5-fold greater contribution of ‘mental’ vs. ‘physical demand’. Flights provoked a 2-3 fold increasing in sympathetic modulation, with 50% greater average autonomic changes in P1 than P2 (D max/min; p<0.05): RRi (P1: D -189/-199 ms; P2: D -164/-177 ms), RMMSD (P1: D -24/-25 ms; P2: D -16/-18 ms), pNN50 (P1: D -19/-20%; P2: D -15/-20%), LF (P1: D 19/24 u.n.; P2: D 19 u.n.), HF (P1: D -19/-23 u.n.; D P2: -18/-19 u.n.), LF/HF (P1: D 4/5; P2: D 3/4). Correlations between NASA-TLX and sympathetic modulation were inverse vs. ‘physical demand’ and ‘overall workload’ (rs= -0.52/-0.63), and direct vs. ‘mental demand’ (rs=0.57), the opposite occurring for parasympathetic modulation (rs=0.47/0.59; rs= -0.45/-0.47; p<0.05). The cognitive performance was unaltered and uncorrelated with NASA-TLX components. Conclusion: Greater perceived workload during military transport flights increased sympathetic and lowered parasympathetic modulation but did not influence cognitive performance.