Muscle is much more than an organ of action and sensation.
Research spanning the last 20 years has revealed that skeletal muscle is an endocrine organ which produces and releases myokines. Myokines work like hormones, by exerting specific endocrine effects on other organs. Myokines also influence muscle metabolism.
Physical activity induces the secretion of myokines from skeletal muscle which generates significant health effects. By contrast, sedentariness induces detrimental health effects including systemic inflammation via visceral adipose. Physical activity triggers myokines that protect against several chronic diseases which share common inflammatory and metabolic profiles.
Physical activity triggers the production and release of myokines which increase insulin sensitivity and lipid metabolism and also promote anti-inflammatory pathways. These effects are associated with the prototypic myokine interleukin-6 (IL-6). During and immediately after exercise IL-6 levels increase by as much as 100-fold.
There are numerous other exercise induced myokines that support healthy physiology and neurobiology and affirm the proposition that exercise is a ‘true polypill’:
– IL-15 appears to have a metabolic role in muscle–fat crosstalk
– IL-8 induces angiogenesis in response to exercise
– Brain-derived neurotrophic factor (BDNF) triggers the use of fat as metabolic fuel. BDNF also supports neurogenesis, synaptogenesis as well as synaptic activity, stability and sensitivity. BDNF levels influence memory formation and low levels are associated with numerous neurocognitive diseases including depression.
Interestingly, stress decreases the expression of BDNF which has the potential to lead to hippocampal atrophy. Atrophy of the hippocampus and other limbic structures has been shown to take place in humans suffering from chronic depression.
BDNF highlights the interdependence of muscle and brain.
Myokines make a strong case for cultivating both brawn and brain through Integrated Embodiment.