Athletes often hear “relax your face” or “try to smile” during hard efforts — and it turns out this advice is backed by solid research. Multiple studies show that deliberately smiling during endurance exercise improves running economy and reduces perceived exertion, leading to better race outcomes.

The Evidence

• Smiling reduces perceived effort and improves running economy
  A 2018 study in Psychology of Sport and Exercise found that runners who intentionally smiled during intervals used more efficient movement patterns and reported lower perceived effort, even at the same pace. This improved “movement economy” means you burn less energy for the same speed.

• Facial relaxation and positive expressions improve physiological responses
  The same research showed that relaxing facial muscles — including smiling — reduces unnecessary tension, helping athletes maintain smoother, more economical form.

• Real‑world ultra‑endurance data confirms the link
  A 2026 Scientific Reports analysis of facial expressions during ultra‑trail racing found that athletes displaying more positive expressions (including smiles) showed better emotional regulation, which is strongly associated with improved pacing and endurance outcomes.

• Smiling influences stress and performance context
  Research on non‑verbal expressions in sport shows that positive facial cues (rewarding smiles) reduce stress responses and improve affective state — both critical for maintaining performance under fatigue.

• Popular science summary of the evidence
  The Conversation highlighted that smiling lowers perceived effort — one of the strongest predictors of endurance performance — making it a simple, effective strategy for runners of all levels.

Why It Works

• Lower perceived effort → better endurance
  When your brain thinks the effort is lower, you can sustain pace longer.

• Reduced muscle tension
  Smiling relaxes facial and upper‑body muscles, improving running economy.

• Positive emotional regulation
  Smiling shifts your psychological state, helping you manage discomfort and maintain focus.

• Feedback loop effect
  A relaxed face promotes relaxed breathing and smoother movement patter

How to Use This in Your Next Race

• Practice smiling during training intervals.

• Use smiling as a cue to relax shoulders and jaw.

• Smile at aid stations, competitors, or spectators to trigger positive affect.

• Pair smiling with mantras or rhythm cues for maximum effect.

Sources: Psychology of Sport & Exercise (2018), Scientific Reports (2026), The Conversation (2018).