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Smile. I Dare You!

It’ll Make You A More Efficient Runner

Ever wondered what determines your race pace?


This is made up of a combination of physiological and psychological factors. Physiological factors include but are not limited to your VO2 max (the highest rate at which oxygen can be extracted, transported and consumed in the process of aerobic adenosine triphosphate synthesis), critical speed (your threshold), running economy (how much oxygen it costs you to do what you’re trying to do) [1,2]. A critical psychological factor is perceived effort, or how hard you feel that you’re working during a run. Effort, after all, dictates if you decide to speed up or slow down.


So how then can you measure effort?


Effort, appears to be all in the face. Research shows that you can make a reasonable estimate of how hard an effort someone is making by measuring the activation of smiling or frowning muscles in their face [3]. Indeed, it’s been proposed that whilst a hard effort will make you frown, frowning might even make that effort feel harder [3].


Perhaps we could all learn a lesson from Kipchoge?

Ever looked back at your race pictures and seen the face of pain? I for one can count myself in. Comparatively, if you re-watch Kipchoge's amazing sub-2-hour marathon in detail, paying close attention to his facial expressions, a common pattern appears. Despite the incredible physical and mental toll that this man was enduring, every few minutes a seemingly cheerful smile spread across his face. The question then is, was Kipchoge enjoying the moment or was there a strategy to this?



What does the science say?

As part of a research study, 24 club-level runners were asked to complete four six-minute running blocks on a treadmill at the same speed [4]. Each six-minute run was performed during a single session, with a two-minute rest between each bout. Throughout the test, the club runners ran whilst wearing a mask, allowing us physiologists to measure how much oxygen it cost them to run at a given speed (running economy)


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 throughout the whole run.


Remarkably 1) the runners were 2.8% more economical (used 2.8% less oxygen to run at the same speed) when smiling than when frowning and 2) were 2.2% more economical when smiling than when adopting their usual focus. Here’s what that oxygen consumption looked like in the four conditions:

To place into context, how significant is a 2.8% improvement to your running economy?


Although smaller than a 4.1% improvement in running economy previously observed from 9 weeks of plyometrics training in a group of elite middle and long-distance runners [5], smiling does not require weeks and months of training. This is something that you can apply tomorrow, with little effort. Sound good to you? Me too.


So how then can you apply smiling to your training and race day performance?


Smiling may be a useful strategy to improve your running economy and to help you feel more relaxed. In contrast, frowning may increase tension and make your run feel harder. What we don’t know, however, is for how long you should smile for. The runners in this study smiled continuously, whereas, Kipchoge only smiled periodically for as little as 30 seconds at a time.


Attempting to smile for the whole duration of your run or race is probably an unrealistic target. Whilst we don’t know for sure if this is going to be sufficient, a genuine periodic smile (30 seconds at a time) is likely to prove effective. Why? It’ll make you feel more relaxed, serving to reduce sensations of effort during your training run or race. This will, in turn, reduce your sympathetic nervous system activity levels (heart rate) and muscle tension, allowing you to run more efficiently.


My top tip is to think of something that will make you smile every time when out on that run, such as a loved one's smile or laugh. Better still, if it’s a race ask family members and/or friends to station themselves at different locations of your race. Ask them to surprise you with something that will make you smile, perhaps an embarrassing picture of you or a joke that only you will get.



(1) Jones AM. The Physiology of the World Record Holder for the Women’s Marathon. Int J Sports Sci Coach 2006;1:101–16. 

(2) Jones AM, Burnley M, Black MI, et al. The maximal metabolic steady state: redefining the ‘gold standard’. Physiol Rep 2019;7:e14098.

(3) de Morree HM, Marcora SM. The face of effort: Frowning muscle activity reflects effort during a physical task. Biol Psychol 2010;85:377–82. 

(4) Brick NE, McElhinney MJ, Metcalfe RS. The effects of facial expression and relaxation cues on movement economy, physiological, and perceptual responses during running. Psychol Sport Exerc 2018;34:20–8. 

(5) Saunders PU, Telford RD, Pyne DB, et al. Short-term plyometric training improves running economy in highly trained middle and long-distance runners. J Strength Cond Res 2006;20:947–54.


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