Noninvasive biochemical monitoring of physiological stress by Fourier transform infrared saliva spectroscopy.

Physical stress affects the immune system, activates the sympathetic (SNS) and parasympathetic (PNS) subsystems of autonomic nervous system (ANS), and increases the activity of the hypothalamic-pituitary-adrenal axis (HPA). The specific response of the major regulatory systems depends on the human functional state. Saliva is a unique diagnostic fluid, the composition of which immediately reflects the SNS, PNS, HPA and immune system response to stress. A new method of saliva biomarker determination by Attenuated Total Reflection Fourier-Transform Infrared (ATR FTIR) spectroscopy has been developed to monitor the exercise induced metabolic changes in saliva from male endurance athletes. The method has been tested using a group of professional athletes by analysing saliva samples collected before and after the exercise, and the saliva composition monitoring by ATR FTIR spectroscopy was shown to be suitable for real-time checking of response to stress.