Mind over body: Interfering with the inner voice is detrimental to endurance performance

In two preregistered experiments, we investigated whether people were less able to push themselves physically when distracted from using their internal language. In both experiments, participants performed 12 cycling trials (Experiment 1: N = 49; Experiment 2: N = 50), each lasting one minute where participants were required to cycle as fast as possible while engaging in either a visuospatial task, a verbal task or with no interference. Participants performed worse in the verbal interference condition compared with the control condition (Experiment 1: d = 0.29; Experiment 2: d = 1). Verbal interference was also significantly worse than visuospatial interference in Experiment 2 (d = 0.43) but only numerically worse in Experiment 1 (d = 0.29). These differences were likely due to a more demanding interference task format in Experiment 2. These experiments indicate that the inner voice plays an important role in top-down control of sustained physical efforts.