Endocannabinoids and heart rate variability alterations after exposure to prolonged intensive physical exercise of the Hellenic Navy SEALs

Abstract

Background

Recent research indicates that endocanabinoids (eCB) and heart rate variability (HRV) are associated with stress-induced experiences. However, these underlying mechanisms have not been elucidated.

Purpose

The aim of the present study is to investigate if exposure to acute and chronic stress promotes measurable changes concurrently to the peripheral eCB ligands and the HRV.

Methods

13 candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (H.N.S.) participated in the study. All subjects underwent mental state examination, while HRV variables in time and frequency domains recordings were acquired. Furthermore, at baseline and 30 days after prolonged and intensive physical exercise hair were collected in order to measure eCB ligands, such as anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the N-acyl ethanolamine (NAE) molecules: palmitoylethanolamide (PEA) and oleoylethanolamide (OEA).

Results

Comparing basal hair concentrations of eCB ligands before and after intensive physical exercise, we found that AEA, PEA and OEA were notably increased (p<0.01, p<0.05 and p<0.01 respectively) whereas no differences were observed regarding the ligand 2-AG. Regarding time domain features of HRV, a strong positive correlation was found between mean HR, AEA and PEA [r(13)=0.934, p<0.05, (r(13)=0.902, p<0.05]. Regarding frequency domain, a strong negative correlation was found between low frequency (LF) HRV and PEA (r(13)=−0.853, p<0.01). No statistically significant associations were noted between high frequency HRV and EC ligands.

Conclusions

These findings suggest that endocannabinoid-HRV interrelations might share a short-term, and long-term adaptability of the changes in self-regulation associated with stress. Further studies are required to determine the validity of peripheral eCB signaling and HRV as a biomarker for different aspects of stress response.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Region of Attica

Psychiatric Disorders and Heart Disease