Monitoring physical fatigue and capacity is important in high-performance environments to optimize the training stimulus and minimize unplanned physical fatigue. For that purpose, accelerometer sensors have emerged as a tool with the potential to measure and reflect changes in runner's acceleration. An accelerometer was used to measure the acceleration patterns which provided an analogue signal that could analyzed further by using different feature extractions. This research was aimed to estimate the location of physical fatigue occurrence in 400 m running. Basically, the experiments were conducted in outdoor track field, 6 subjects were involved, with age ranging between 19-24 years. In this study, two features have been used which are root mean square (RMS) and player load (PL) to indicate fatigue. The obtained results have shown that there were declines in the player load values in the last 150 m of running for most of the subjects which indicate occurrence of physical fatigue. On the other hand, some subjects have tried to save their energy in the 2nd and 3rd 100 m to speed up again in the last 100 m but there were obvious decrements in their player load in 400 m compared to the 1 100 m of running.
