title: G-loading and vibration effects on heart and respiration rates.
abstract: BACKGROUND
  Operational environments expose pilots and astronauts to sustained acceleration (G loading) and whole-body vibration, alone and in combination. Separately, the physiological effects of G loading and vibration have been well studied; both have effects similar to mild exercise. The few studies of combined G loading and vibration have not reported an interaction between these factors on physiological responses.
  
  
  METHODS
  We tested the effects of G loading (+1 and +3.8 G(x)) and vibration (0.5 gx at 8, 12, and 16 Hz), alone and in combination, on heart and respiration rate.
  
  
  RESULTS
  We observed an effect of G loading on heart rate (average increase of 23 bpm, SD 12) and respiration rate (average increase of 5 breaths per minute, SD 5), an effect of vibration on heart rate, and an interaction on heart rate. With vibration, we observed heart rate increases of 4 bpm (SD: 3) with no increase in respiration rate. In the +1 G(x) condition, the largest heart rate increase occurred during low-frequency (8 Hz) vibration, while at +3.8 G(x), the largest heart rate increase occurred during high-frequency (16 Hz) vibration, demonstrating interaction.
  
  
  CONCLUSIONS
  Consistent with previous reports, our G-loading and vibration effects are similar to mild exercise. In addition, we observed an interaction between G loading and vibration on heart rate, with maximum heart rates occurring at a higher vibration frequency at +3.8 G(x) compared to +1 G(x). The observed interaction demonstrates that G-loading and vibration effects are not independent and can only be properly assessed during combined exposure.
authors.affiliation: NASA Ames Research Center, Moffett Field, CA, USA.
authors.forename: Angelica
authors.initials: A
authors.lastname: Godinez
authors.forename: Dorion B
authors.initials: DB
authors.lastname: Liston
authors.forename: Ruthie
authors.initials: R
authors.lastname: Ayzenberg
authors.forename: William B
authors.initials: WB
authors.lastname: Toscano
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Cowings
authors.forename: Leland S
authors.initials: LS
authors.lastname: Stone
mesh_terms: D000054:Acceleration; D000328:Adult; D000337:Aerospace Medicine; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D018471:Hypergravity; D008297:Male; D008875:Middle Aged; D056152:Respiratory Rate / Q000502:physiology*; D014732:Vibration