anchor.diff:  S2ESBP: stage 2 exercise systolic blood pressure
   
   
  +SDNN: standard deviation of the normal-to-normal inter beat intervals
  +
  +
   serum TG: serum total triglyceride content
   
   
  
positive.code: RDW: red cell distribution width
  
  
  RQmax: maximum respiratory quotient during treadmill fitness test
  
  
  
negative.code: 
  PUFA: polyunsaturated fatty acids
  
  
  pvRSA/HF: peak-valley respiratory sinus arrhythmia or high frequency power
  
  === Q
  
  QC: quality control
  