Introduction Moving in real environments requires to consider not only ecological motor tasks (e.g., curvilinear walking), but also the cognitive load associated with the motor performance [1,2]. Wearable technology provides non-invasive monitoring solutions for both aspects, through inertial sensors and functional Near-Infrared Spectroscopy (fNIRS) technique. Specifically, fNIRS assesses cortical activity through the hemodynamic response of the brain [3] and can be performed while the participant freely moves in the environment [3,4]. In this context, the prefrontal cortex (PFC) is of particular interest: it regulates executive functions and has the potential to reveal crucial information related to cognitive processes and dynamic gait indices [1,3,4]. While it is well known that different motor tasks are characterized by different PFC activations, it is not clearly understood how PFC activation changes with increased complexity of balance locomotion tasks yet. Therefore, the study aims at filling this gap investigating motor-cognitive interference in balance and gait tasks of increasing difficulty. Methods Twenty healthy young adults (11 females, 24.4±2.7 years) randomly performed four different motor tasks of 60 s each related to dynamic (linear walking, LW, and tandem walking, TW) and static (doubleleg stance, DLS, and single-leg stance, SLS) balance while wearing: i) a fNIRS brain cap (Brite 24, Artinis, The Netherlands) to measure the PFC changes in oxygenated hemoglobin (ΔO2Hb), and ii) 4 synchronized measurement units (IMUs, Opal, APDM, USA) at sternum, pelvis and both lateral malleoli to quantify gait and balance motor patterns. Repeated measures ANOVA (ΔO2Hb) and t-tests (IMUs) were computed to investigate differences among tasks. Results fNIRS (top panel) and IMUs (bottom panels) results are displayed in Fig. 1. Discussion As expected, more challenging motor tasks (TW and SLS) require greater PFC activation, suggesting the use of additional attentional resources during tasks of increased difficulty. In addition, motor performance suffers of tasks complexity, as clearly emerge from dynamic gait indices and postural parameters. This study lays foundation for better understanding the motor-cognitive interference in ecological gait and balance tasks.