Recent research has found a connection between dopamine and whether we feel the exercise that we are doing is easy or hard. Interestingly, the findings “suggest that dopamine level is a critical factor in helping people accurately assess how much effort a physical task requires, which can significantly affect how much effort they’re willing to put forth for future tasks. For example, if someone perceives that a physical task will take an extraordinary amount of effort, they may be less motivated to do it.” The findings could “eventually lead to more effective ways to help people establish and stick with exercise regimens, new treatments for fatigue associated with depression and many other conditions, and a better understanding of Parkinson’s disease,” which is “marked by a loss of dopamine-producing cells in the brain over time.”