Effects of exercise stress on the endocannabinoid system in humans under field conditions
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The effects of physical exercise stress on the endocannabinoid system in humans are almost unexplored. In this prospective study, we investigated in a crossover design and under field conditions at different altitudes the effects of physical exercise on the endocannabinoid system (ECS) in 12 trained healthy volunteers. For determination of alterations on the ECS three different protocols were analyzed: Protocol A (physical exercise at lower altitude) involved strenuous hiking below 2,100 m, whereas Protocol B (physical exercise by active ascent to high altitude) involved hiking up to 3,196 m, an accommodation at the cottage and a descent the next day. Protocol C (passive ascent) included a helicopter ascent to 3,196 m, an overnight stay at this altitude and a flight back to the base camp the following day. The cumulative hiked altitude in Protocol A and B was comparable (~1,650 m). The blood EC concentrations of anandamide increased significantly in Protocol A/B from baseline (T0) 0.12 ± 0.01/0.16 ± 0.02 (mean ± SEM) to 0.27 ± 0.02/0.42 ± 0.02 after exercise (T1) (p < 0.05). Anandamide levels in Protocol C remained stable at 0.20 ± 0.02. We conclude that the ECS is activated upon strenuous exercise whereas the combination with hypoxic stress further increases its activity. The reduced partial pressure of oxygen at high altitude alone did not affect this system. In summary, physical exercise activates the endocannabinoid system, whereas the combination with high altitude enhances this activation. This discloses new perspectives to adaptation mechanisms to physical exercise.
KeywordsEndocannabinoids Anandamide 2-AG Exercise Sport
The authors thank the volunteers of the South Tyrolean Mountain Rescue Service who generously spent their time and participated with enthusiasm. We also thank Dr. G. Andergassen, Dr. G. Rammlmair, Prof. F. Christ, Dr. S. Kofler, Dr. M. Choukèr, M. Hoelzl, O. Zorzi, Dr. C. Moser, Dr. M. Niklas, Dr. J. Abicht, S. Schröpfer and Prof. Dr. M. Vogeser for continuous help during the study. This field study was supported by a research grant from the South Tyrolean Department of Health and by Siemens Medical Solutions, Munich, Germany, the Department of Anaesthesiology, and Department of Intensive Care Medicine of Brixen (Italy) and Munich (Germany), respectively.
Conflict of interest
The authors have no conflicts of interest or financial ties to disclose.
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