title: An accelerometer-based earpiece to monitor and quantify physical activity.
abstract: BACKGROUND
  Physical activity is important in ill-health. Inexpensive, accurate and precise devices could help assess daily activity. We integrated novel activity-sensing technology into an earpiece used with portable music-players and phones; the physical-activity-sensing earpiece (PASE). Here we examined whether the PASE could accurately and precisely detect physical activity and measure its intensity and thence predict energy expenditure.
  
  
  METHODS
  Experiment 1: 18 subjects wore PASE with different body postures and during graded walking. Energy expenditure was measured using indirect calorimetry. Experiment 2: 8 subjects wore the earpiece and walked a known distance. Experiment 3: 8 subjects wore the earpiece and 'jogged' at 3.5 mph.
  
  
  RESULTS
  The earpiece correctly distinguished lying from sitting/standing and distinguished standing still from walking (76/76 cases). PASE output showed excellent sequential increases with increased in walking velocity and energy expenditure (r2 > .9). The PASE prediction of free-living walking velocity was, 2.5 +/- (SD) 0.18 mph c.f. actual velocity, 2.5 +/- 0.16 mph. The earpiece successfully distinguished walking at 3.5 mph from 'jogging' at the same velocity (P < .001).
  
  
  CONCLUSIONS
  The subjects tolerated the earpiece well and were comfortable wearing it. The PASE can therefore be used to reliably monitor free-living physical activity and its associated energy expenditure.
authors.affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, MN, USA.
authors.forename: Chinmay
authors.initials: C
authors.lastname: Manohar
authors.forename: Shelly
authors.initials: S
authors.lastname: McCrady
authors.forename: Ioannis T
authors.initials: IT
authors.lastname: Pavlidis
authors.forename: James A
authors.initials: JA
authors.lastname: Levine
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002153:Calorimetry, Indirect / Q000295:instrumentation*; D004423:Ear; D004734:Energy Metabolism / Q000502:physiology*; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009043:Motor Activity / Q000502:physiology*; D015203:Reproducibility of Results; D022722:Thermogenesis / Q000502:physiology; D055815:Young Adult