Research recently published within the journal of Physiology and Behaviour by PESP members Daniel Taylor and Dr Mark F Smith has revealed the physiological consequence of multi-sport activity, such as triathlon, on overall performance. This study examined how residual fatigue affects the relationship between ratings of perceived exertion (RPE), physiological responses, and pacing during triathlon performance. Findings indicated that our perception of effort, measured through our rating of perceived exertion appears to be a key pace regulator during multi-sport endurance performance and can be used to further examine what limits our endurance capability.