Engaging in cognitively demanding tasks can lead to decreased physical performance and increased perceived effort. These negative carryover effects suggest there are common neurological determinants of effort sensation during cognitive and physical tasks. The purpose of this study was to explore the aftereffects of cognitive effort exertion on perceptions of effort, force production, and muscle activation during a physically-demanding task. Using a crossover design, participants (N=21) completed a 10-minute high-effort cognitive task and a low-effort cognitive task on separate days. On both days, the cognitive tasks were followed by an endurance handgrip trial in which participants squeezed a dynamometer at 15% of their maximum voluntary contraction (MVC) with their dominant hand until exhaustion. Additionally, participants intermittently (30-sec intervals) squeezed another dynamometer with their non-dominant hand to match the perceived effort required to sustain the endurance squeeze. Surface EMG measured forearm muscle activation in both arms and ratings of perceived exertion (RPE) were recorded prior to each effort-matching trial. Participants performed equally on the endurance trials (p=0.93, Cohen's d=0.02) with similar RPE throughout both trials (p=0.91, ES<0.01). Following the high-effort cognitive task, forces produced by the non-dominant arm while effort-matching showed decreased levels (p=0.10, ES=0.13), which were accompanied by lower levels of muscle activation (p=0.02, ES=0.25). In short, participants generated less force and less muscle activation despite perceiving the task to be equally effortful. Results contribute to the literature showing negative carryover effects of cognitive effort exertion on physical performance and suggest perceptions of physical effort are centrally mediated.