# The Effects of a Simulated Duathlon on Trunk Motion: A Sensor Based Approach
## 1 Introduction
For instance, as [PERSON] and [PERSON] [19] noted, running economy is an intricate construct that implies the sum of various metabolic, cardiorespiratory, biomechanical, and neuromuscular characteristics during submaximal running. When the trunk is considered, the addition of cycling and the associated loadings on the neuromuscular system can modify spatiotemporal variables in running, including trunk gradient and trunk posture, which can impact running economy. Thus, from a performance optimisation perspective, a continuing area of focus for coaches and scientists is determining how to reduce these biomechanical complications. The challenge is to improve sporting performance. Yet, wearable technology can allow applied field-based data collection, which has greater ecological validity than traditional laboratory-based methods. Developments in wearable sensor technology (wearables) have allowed for the detection of triaxial movement that is capable of valid measurement in the field. Wearables play an instrumental role in sports performance and justify the adoption of more unobtrusive and portable devices that can be used in characteristic training scenarios [20; 21]. Technological developments have empowered athletes and coaches to track functional movements, workload, biomechanical, and biovital markers that utilise wearable sensors to maximize performance [22]. While wearables, specifically accelerometer usage, have increased, there have been few studies (e.g., [3; 9]) examining the use of these proprietary measures in duathlon as an alternative to laboratory-collected data. In duathlon, much of the athlete's motion in both running and cycling occurs in the sagittal plane. Therefore, if compensatory, or unwanted or excessive, movement of additional body segments occur in the frontal or transverse plane due to increased postural sway, a performance decrement is probable. Inconspicuous wearable devices such as triaxial accelerometers can be applied in the field to record variations to trunk motion. This applied method is advantageous due to data being largely more reflective of an athlete's representative cycling and running performance. This approach may be a better reflection of an athlete's true and self-determined kinematics [12]. In a duathlon context, knowledge, and a greater understanding of trunk accelerations, that is, using triaxial accelerometers in an applied and representative outdoor setting, is beneficial for two reasons. Firstly, the obtained data allow for quantification in a more realistic setting compared to the typical laboratory environment. Secondly, obtainment of data in a simulated duathlon may help inform training interventions in the three sequential disciplines in what remains a relatively underresearched sport compared to triathlon. Accordingly, our objective was to compare the magnitude of trunk acceleration between a single run prior to cycling and the final run of a duathlon and to compare overall performance times in running pre- and post-cycling in duathlon. We hypothesized that (1) the magnitude of trunk acceleration would increase during the initial bout of the duathlon, that is, running after cycling, and that (2) running performance time after cycling (mm:ss) would decrease compared to running prior to cycling.