Understanding stressors in combination: a continued challenge for human performance.

Personnel within occupational employment (e.g., military/emergency services) are exposed to various stressors concurrently including psychological, cognitive, physical and environmental. Historically, stressors have been considered and studied in isolation which is not representative of reality. Assessing stressors in combination is challenging for researchers owing to the study designs required to explore such interactions. Complex study protocols can lead to logistical challenges and high demands on resources and participants. Very few studies within the literature have been found to explore multiple stressors, although in recent years, this has started to change for the better. Understanding how numerous stressors interact, whether effects on performance are additive, synergistic or antagonistic, is important. Without this, the true impact of stressors will remain unknown, and the health and performance of those within arduous occupational roles may not be optimised. This review aims to (1) explore how different study designs have enabled the exploration of the effects of combined stressors on human performance outcomes in controlled laboratory settings, simulated field studies and field-based settings, and (2) outline how future research can develop methodologies that study combinations of stressors in occupational roles.