Recently, attentional focus studies involving force production have demonstrated that when participants focused externally motor units were recruited more efficiently and muscular communication was enhanced. When participants focused internally, however, increased "noise" was incorporated into the neuromuscular system resulting in energy waste. The present study explored the effects of an external or internal focus of attention in the isometric wall sit endurance test. Since motor unit recruitment is more efficient under an external focus, it was hypothesized that participants (n = 23) would have a higher endurance time when they focused externally (ex. I want you to focus on pretending like you are sitting in a chair through the duration of the trial) rather than internally (ex. I want you to focus on keeping your knee at 90 degrees through the duration of the trial). Results revealed when participants focused externally they had a significantly higher endurance time (68.41 ± 34.12 sec) than when they focused internally (60.22 ± 34.54 sec). Participants also adopted the correct attentional focus in a majority of the endurance trials (70% and 69% for the external and internal conditions, respectively). This was the first study to demonstrate the benefits of an external focus over an internal focus in an isometric wall sit endurance test. Future studies should use biomechanical analyses such as EMG and kinematic measures and perceived force measures such as RPE to explore the reasons why an external focus provided performance benefits.