For athletes of all levels, endurance — how long they can keep going at their chosen sport — is made up of physiological and psychological factors.
Physiological factors include cardiovascular fitness, and how efficient an athlete is at using energy (their “movement economy”).
A critical psychological factor, on the other hand, is perceived effort, or how hard we feel we are working during an activity. The lower our perceived effort, the easier we feel that an activity is.
Crucially, any strategy that reduces how much an athlete perceives it to be an effort generally has a positive effect on endurance performance. One of the more surprising approaches could be to deliberately manipulate one’s facial expression.
As peculiar as it may seem, many top athletes, including Olympic marathon gold medallist Eliud Kipchoge, strategically use periodic smiling during performance to relax and cope.