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.
In addition, research has also suggested that intentional smiling may reduce effort perception during physical activity in comparison with frowning. However, until we began our latest investigation, no study had looked into the actual effects of facial expressions on movement economy or perceived effort during endurance activity that has a longer duration.
We asked 24 club-level runners to complete four six minute running blocks on a treadmill. Each six minute run was performed during a single session, with a two minute rest between each bout. During each run, participants either smiled (specifically a real or “Duchenne” smile, and not a fake smile), frowned (runners mimicked their own facial expression during intense running), attempted to consciously relax their hands and upper-body (by imagining they were holding a crisp but trying not to break it), or adopted their normal focus of attention during running.
Each participant also wore a breathing mask that allowed us to measure how much oxygen they consumed while running. By measuring the oxygen, we could work out how much energy the runner had used. After each run, we asked participants to report on a number of perceptual responses, including their perceived effort during the preceding six minutes.
Our key finding was that participants were most economical (they used less energy) while smiling. Remarkably, participants were 2.8% more economical when smiling than frowning, and 2.2% more economical in comparison with the normal thoughts condition. These reductions would be enough to expect a meaningful improvement in performance in race conditions.
Participants also reported a higher perceived effort when frowning than smiling or when attempting to relax their hands and upper body.
Eliud Kipchoge smiles during the 44th BMW Berlin Marathon. dominika zarzycka/Shutterstock