Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high’

Abstract

SUMMARYHumans report a wide range of neurobiological rewards following moderate and intense aerobic activity, popularly referred to as the ʻrunnerʼs highʼ, which may function to encourage habitual aerobic exercise. Endocannabinoids (eCBs) are endogenous neurotransmitters that appear to play a major role in generating these rewards by activating cannabinoid receptors in brain reward regions during and after exercise. Other species also regularly engage in endurance exercise (cursorial mammals), and as humans share many morphological traits with these taxa, it is possible that exercise-induced eCB signaling motivates habitual high-intensity locomotor behaviors in cursorial mammals. If true, then neurobiological rewards may explain variation in habitual locomotor activity and performance across mammals. We measured circulating eCBs in humans, dogs (a cursorial mammal) and ferrets (a non-cursorial mammal) before and after treadmill exercise to test the hypothesis that neurobiological rewards are linked to high-intensity exercise in cursorial mammals. We show that humans and dogs share significantly increased exercise-induced eCB signaling following high-intensity endurance running. eCB signaling does not significantly increase following low-intensity walking in these taxa, and eCB signaling does not significantly increase in the non-cursorial ferrets following exercise at any intensity. This study provides the first evidence that inter-specific variation in neurotransmitter signaling may explain differences in locomotor behavior among mammals. Thus, a neurobiological reward for endurance exercise may explain why humans and other cursorial mammals habitually engage in aerobic exercise despite the higher associated energy costs and injury risks, and why non-cursorial mammals avoid such locomotor behaviors.

Gracility of the modernHomo sapiensskeleton is the result of decreased biomechanical loading

“…With the emergence of Homo erectus ∼1.8 million y ago, paleontological and archaeological evidence indicate a major shift in hominin evolution characterized by increases in brain and body size (53), improved locomotor efficiency (54), larger home ranges, and increased mobility (55). This long evolutionary history of high levels of terrestrial mobility in the genus Homo, together with the evidence of selection for endurance running (56,57), strongly suggests that the human locomotor skeleton evolved in a mechanical and physiological context that involved persistent and frequent loading throughout life. This study provides support for the assertion that contemporary humans live in a cultural and technological milieu incompatible with our evolutionary adaptations (58), and highlights the importance of physical activity and exercise for bone health and the attenuation of age-related bone loss, osteoporosis, and fracture risk.…”

Systematic review: Efficacy and safety of medical marijuana in selected neurologic disorders [RETIRED]

“…CB-2 receptors are found in the periphery, including lymph tissue, and in lower concentrations in some brain regions, including the periaqueductal gray. Activation through G-coupled membrane proteins causes physiologic responses expected from these regions, including feelings of well-being or psychosis (depending on the "dose" of THC), impaired memory and cognitive processing, slowed locomotor function, as well as antinociceptive, 3 antiemetic, antispasticity, and sleep-promoting effects. Receptor activation inhibits adenylate cyclase, converting cyclic adenosine monophosphate to adenosine triphosphate, and inhibits release of multiple neurotransmitters, including acetylcholine, dopamine, and glutamate, when neuronal excitation is present.…”

A Review on exercise and blood cells

“…The major short term effect of exercise is euphoria, which is colloquially known as "runner's high" in distance running or "rower's high" in crew (Raichlen et al, 2012). Recent researches and medical reviews have shown that endogenous euphoriants such as betaphenylamide (stimulant), beta-endorphin (an opiod), and anandamide are responsible for producing exercise related euphoria.…”