title: Heart-Rate Variability During Deep Sleep in World-Class Alpine Skiers: A Time-Efficient Alternative to Morning Supine Measurements.
abstract: BACKGROUND
  It is increasingly popular to use heart-rate variability (HRV) to tailor training for athletes. A time-efficient method is HRV assessment during deep sleep.
  
  
  OBJECTIVE
  To validate the selection of deep-sleep segments identified by RR intervals with simultaneous electroencephalography (EEG) recordings and to compare HRV parameters of these segments with those of standard morning supine measurements.
  
  
  METHODS
  In 11 world-class alpine skiers, RR intervals were monitored during 10 nights, and simultaneous EEGs were recorded during 2-4 nights. Deep sleep was determined from the HRV signal and verified by delta power from the EEG recordings. Four further segments were chosen for HRV determination, namely, a 4-h segment from midnight to 4 AM and three 5-min segments: 1 just before awakening, 1 after waking in supine position, and 1 in standing after orthostatic challenge. Training load was recorded every day.
  
  
  RESULTS
  A total of 80 night and 68 morning measurements of 9 athletes were analyzed. Good correspondence between the phases selected by RR intervals vs those selected by EEG was found. Concerning root-mean-squared difference of successive RR intervals (RMSSD), a marker for parasympathetic activity, the best relationship with the morning supine measurement was found in deep sleep.
  
  
  CONCLUSIONS
  HRV is a simple tool for approximating deep-sleep phases, and HRV measurement during deep sleep could provide a time-efficient alternative to HRV in supine position.
authors: David
authors: D
authors: Herzig
authors: Moreno
authors: M
authors: Testorelli
authors: Daniela Schäfer
authors: DS
authors: Olstad
authors: Daniel
authors: D
authors: Erlacher
authors: Peter
authors: P
authors: Achermann
authors: Prisca
authors: P
authors: Eser
authors: Matthias
authors: M
authors: Wilhelm
mesh_terms: D000328:Adult; D004569:Electroencephalography; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D064797:Physical Conditioning, Human; D012865:Skiing / Q000502:physiology*; D012890:Sleep / Q000502:physiology*; D016683:Supine Position; D055815:Young Adult
keywords: athletes; cardiac autonomic nervous system; training; vagus-related HRV indices