No effect of facial expression on running economy in collegiate soccer players

The facial feedback hypothesis (FFH) states that activation of facial muscles (i.e., smiling and frowning) can elicit emotional experiences within an individual. A positive emotional experience could result in a more “relaxed state” and result in improved running economy (RE). The purpose of this study was to determine if smiling while running would lead to an improvement in RE among a group of collegiate soccer players. Twenty-four Division III collegiate soccer players (females n = 14, males n = 10) completed four, six-minute running blocks at 70% of velocity at VO 2 max. The order of bouts was randomised with participants serving as their own controls. Participants completed running blocks while smiling (Smile), frowning (Frown), consciously relaxing their hands and upper bodies (Relax), and running as they “normally” would (Control). Each block was separated by two minutes of passive rest. Cardiorespiratory responses were recorded continuously, and participants reported perceived exertion (RPE) after each condition. A repeated measures analysis of variance (ANOVA) was run on all primary variables with a significance level set a priori at 0.05. There were no significant differences in RE across conditions (p > 0.05; Smile: mean = 33.7 mL∙kg -1 ∙min -1 , SD = 4.4; Frown: mean = 34.2 mL∙kg -1 ∙min -1 , SD = 4.1; Relax: mean = 34.2 mL∙kg -1 ∙min -1 , SD = 4.1; Control: mean = 34.2 mL∙kg -1 ∙min -1 , SD = 3.9). Our findings suggest smiling does not significantly improve RE among a group of collegiate soccer players. Further studies should examine this topic in other athlete groups and at various running intensities.