title: Miniaturized sensors to monitor simulated lunar locomotion.
abstract: BACKGROUND
  Human activity monitoring is a useful tool in medical monitoring, military applications, athletic coaching, and home healthcare. We propose the use of an accelerometer-based system to track crewmember activity during space missions in reduced gravity environments. It is unclear how the partial gravity environment of the Moorn or Mars will affect human locomotion. Here we test a novel analogue of lunar gravity in combination with a custom wireless activity tracking system.
  
  
  METHODS
  A noninvasive wireless accelerometer-based sensor system, the activity tracking device (ATD), was developed. The system has two sensor units; one footwear-mounted and the other waist-mounted near the midlower back. Subjects (N=16) were recruited to test the system in the enhanced Zero Gravity Locomotion Simulator (eZLS) at NASA Glenn Research Center. Data were used to develop an artificial neural network for activity recognition.
  
  
  RESULTS
  The eZLS demonstrated the ability to replicate reduced gravity environments. There was a 98% agreement between the ATD and force plate-derived stride times during running (9.7 km x h(-1)) at both 1 g and 1/6 g. A neural network was designed and successfully trained to identify lunar walking, running, hopping, and loping from ATD measurements with 100% accuracy.
  
  
  CONCLUSIONS
  The eZLS is a suitable tool for examining locomotor activity at simulated lunar gravity. The accelerometer-based ATD system is capable of monitoring human activity and may be suitable for use during remote, long-duration space missions. A neural network has been developed to use data from the ATD to aid in remote activity monitoring.
authors.affiliation: University of Washington, Seattle, WA 98195-6500, USA.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Hanson
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Gilkey
authors.forename: Gail P
authors.initials: GP
authors.lastname: Perusek
authors.forename: David A
authors.initials: DA
authors.lastname: Thorndike
authors.forename: Gilead A
authors.initials: GA
authors.lastname: Kutnick
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Grodsinsky
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Rice
authors.forename: Peter R
authors.initials: PR
authors.lastname: Cavanagh
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008904:Miniaturization; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D016081:Moon; D012775:Shoes; D012984:Software; D014893:Weightlessness