After years in the movement profession I am humbled by the complexity and interdependence of the body. When I first began I would view the following as, ‘a hamstring stretch’.
I now think back to the basics from anatomy and physiology class. There are 11 systems in the human body. The Cardiovascular system is working hard to provide gas exchange and tissue nourishment through the circulatory system while regions are lengthening. The Digestive system peristalsis may be facilitated through pressure gradients. The Endocrine system may be responding in various ways such as increasing blood endorphine levels in response to the intensity of the stretch. The Integumentary system is involved allowing excursion through motion segments because of it’s visco-elastic components. The Lymphatic system is being stimulated through extrinsic pumps to facilitate intrinsic lymph flow. The Muscular system at it’s respective region is being lengthened and shortened simultaneously in all 3 planes of movement. The Nervous system is likewise being tensioned, facilitated, and inhibited allowing for perception of the stimulus. The Renal system is working to preserve sodium for the re-absorption of water and maintaining tissue hydration thus reducing the perceived need for urination during activity. The Reproductive system may be reactive in producing hormonal response such as testosterone in males. The Respiratory system is working to provide gas exchange and nourish oxygen dependent tissues. And of course the Skeletal system may be reacting to the stimulus by creating greater bone density to respond to gravity and ground reaction force.
The question becomes what is not affected during this stretch. Thus another reason why this website is entitled Movement for Life since many of these systems perform optimally when we move and affect our surrounding environment. We are made to move.