The human factors engineering (HFE) process supports the design and development of medical devices, especially novel devices requiring clinical investigation. The typical culmination of the HFE process prior to market approval is a human factors (HF) validation study, with specific requirements of participant, environment and task representation that carry a financial and temporal burden for medical device manufacturers. Whilst strongly recommended ahead of clinical investigations by regulators (and the authors), the prescribed methodology for HF validation studies required for pre-market approval may be excessive ahead of a clinical investigation during the development process. However, the stringent nature of HF validation studies will support effective clinical investigation design and minimise risks of poor clinical outcome or compliance. This paper provides recommendations in what to consider when determining what type of HF study to conduct ahead of each clinical investigation phase as well as insights into the symbiotic benefits of HFE and clinical investigations.