title: Energy expenditure of genuine laughter.
abstract: OBJECTIVE
  To measure energy expenditure (EE) and heart rate (HR) during genuine laughter.
  
  
  METHODS
  Experimental trial of viewing film clips in four cycles either intended to evoke laughter (humorous -10 min) or unlikely to elicit laughter (not humorous -5 min) under strictly controlled conditions of a whole-room indirect calorimeter equipped with audio recording system.
  
  
  METHODS
  Forty five adult friend dyads in either same-sex male (n=7), same-sex female (n=21) and mix-sex male-female (n=17); age 18-34 years; body mass index 24.7+/-4.9 (range 17.9-41.1).
  
  
  METHODS
  Energy expenditure in a whole-room indirect calorimeter, HR using Polar HR monitor. Laugh rate, duration and type from digitized audio data using a computerized system and synchronized with HR and EE results.
  
  
  RESULTS
  Laughter EE was 0.79+/-1.30 kJ/min (0.19+/-0.31 kcal/min) higher than resting EE (P<0.001, 95% confidence interval=0.75-0.88 kJ/min), ranging from -2.52 to 9.67 kJ/min (-0.60-2.31 kcal/min). Heart rate during laughter segments increased above resting by 2.1+/-3.8 beats/min, ranging from -7.6 to 26.8 beats/min. Laughter EE was correlated with HR (r (s)=0.250, P<0.01). Both laughter EE and HR were positively correlated with laughter duration (r (s)=0.282 and 0.337, both P<0.001) and rate (r(s)=0.256 and 0.298, both P<0.001).
  
  
  CONCLUSIONS
  Genuine voiced laughter causes a 10–20% increase in EE and HR above resting values, which means that 10–15 minutes of laughter per day could increase total EE by 10–40 kJ (2–10 kcal) [corrected].
authors.affiliation: Department of Medicine, Vanderbilt University, Nashville, TN, USA. maciej.buchowski@vanderbilt.edu
authors.forename: M S
authors.initials: MS
authors.lastname: Buchowski
authors.forename: K M
authors.initials: KM
authors.lastname: Majchrzak
authors.forename: K
authors.initials: K
authors.lastname: Blomquist
authors.forename: K Y
authors.initials: KY
authors.lastname: Chen
authors.forename: D W
authors.initials: DW
authors.lastname: Byrne
authors.forename: J-A
authors.initials: JA
authors.lastname: Bachorowski
mesh_terms: D000293:Adolescent; D000328:Adult; D001835:Body Weight / Q000502:physiology; D002153:Calorimetry, Indirect / Q000379:methods; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007845:Laughter / Q000502:physiology*; D008297:Male; D013997:Time Factors