title: Heart rate variability and critical flicker fusion frequency changes during and after parachute jumping in experienced skydivers.
abstract: OBJECTIVE
  The purpose of this study was (1) to further explore the heart rate dynamics and assess a potential cardiovascular risk in response to 4000 m jumps in experienced skydivers; (2) to assess whether there is an impact of such jumps on skydivers' cortical arousal or not, which may impact their decision making processes.
  
  
  METHODS
  18 experienced skydivers performed successive jumps from a plane at 4000 m of height. Heart rate dynamics and cortical arousal were assessed by the use of heart rate variability and Critical Flicker Fusion Frequency (CFFF), respectively.
  
  
  RESULTS
  CFFF did not differ between the three measurement time points (p > 0.05). Mean heart rate increased during the jump (p < 0.001) and came back to pre-jump values after the jump (p < 0.001). Percentage of the differences of successive NN intervals greater than 50 ms (pNN50) decreased during the jump (p < 0.001) and kept lower values after the jump compared to pre-jump (p < 0.05). High-frequency power (HF) did not differ during the jump (p > 0.05) but decreased after the jump compared to both pre-jump (p < 0.01) and jump (p < 0.05). Sample entropy decreased during the jump (p < 0.001) and came back to pre-jump values after the jump (p > 0.05).
  
  
  CONCLUSIONS
  These results confirm a vagal input reduction associated with a rise of the sympathetic tone during the jump and suggests that the experienced skydiver is not exposed to a high cardiovascular risk. This study also shows that environmental stresses induced by free fall could not hamper the perceptual vigilance of experienced skydivers.
authors.affiliation: Environmental, Occupational, Ageing and Integrative Physiology Laboratory, Haute Ecole Paul-Henri Spaak, Brussels, Belgium, mcavalade@hotmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Cavalade
authors.forename: V
authors.initials: V
authors.lastname: Papadopoulou
authors.forename: S
authors.initials: S
authors.lastname: Theunissen
authors.forename: C
authors.initials: C
authors.lastname: Balestra
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D005425:Flicker Fusion / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012307:Risk Factors; D013312:Stress, Physiological / Q000502:physiology*