by Jessica Hill, PT, DPT, CSCS
“Thou art of the Jungle and not of the Jungle.”
– R Kipling, The Jungle Book
Last winter I hit a rough patch. There was tremendous stress and uncertainty in several crucial areas of my life, and it manifested as physical tension and agitation. I got home late from clinic one night and could feel the rock on my chest that was the anxiety I carried at that time. I headed out for some air and exercise. I put on two layers of thermals, hat and gloves and speed-walked uphill through the VT cold and dark to a playground a mile away. I was doing a short circuit of calisthenics when the rings and monkey bars caught my eye. I grabbed the rings for the first time in years and could feel my body fight the first full body distraction, a short hang. I hopped back up again and could feel my arms, shoulder blades, and torso settle into the hang, and the apprehension passed. The third time I hopped up I started to swing a little, and I could feel the day roll off me and the calm come. The change in my mood and affect was striking. Walking home I felt light and happy. The next day my upper back and hips felt different – loose and comfortable. I was standing more upright. I was less irritable and anxious in general. I knew I had found something I needed, and I went back to the rings and bars every other day for weeks. I am over 40, and I know in a very real way that I need to ease slowly into things I haven’t done in a while– especially in the cold! I worked up to traversing the bars with a steady and relaxed reciprocal swing and progressed to the rings. The motions became more fluid, less muscular and more inertial. And it always made me feel calm.
I spoke to a colleague about this experience, and she said her autistic child would hang from monkey bars to calm down. She used it as a strategy to diffuse his meltdowns. I thought that was really interesting and went online to see if anyone else had anything to say about it. I found first- and second-hand accounts of kids on the spectrum using suspension and swinging to achieve calm, focus, and an overall down-regulation from over-stimulation. I hunted on PubMed to see if anyone had directly studied the effects of suspension and swinging on stress, anxiety, and sympathetic tone and struck out keyword after keyword. This led to looking at the question indirectly and reading in disciplines I do not usually frequent. Mitch and I got into a conversation about this, and he asked me if I would put together some thoughts regarding my findings.
Brachiation is defined as a form of locomotion that involves swinging from tree limb to tree limb using the upper limbs and alternately supporting the body under each forelimb. I want to discuss brachiation from a couple of vantage points. The first is more speculative due to a paucity of information in the literature – the neurophysiological aspects. The second addresses the mechanical aspects pertaining to structure and function of the evolving and devolving human form. This is a thinking-out-loud piece about possible implications of movement that go beyond getting from one place to another. It is not meant as a treatment recommendation for people on the spectrum as nervous systems and the stimuli that speak to them vary like snowflakes.
A Polish group, Szot et al, performed a six month case study with an autistic child that included intense aquatic and gymnasium exercise, activities chosen for their high proprioceptive input value. The group noted that “increased kinetic activity resulted in … a new status of functional balance characterized by smaller sensitivity in reacting to unfavourable stimuli” in the child. This group proposed a mechanism of action that included a feedback loop between receptors receiving external stimuli from intense movements and process centers in the cortex. More recent work in the study of autism has gone down a similar pathway and has focused on studying an apparent disruption of global integration between the processing of information from interoceptors and exteroceptors (Noel et al). Hatfield et al discuss interoception as the perception of physiological feedback from the body. Groups have recently shown interoception to be associated with cognitive, emotional, and affective functions, and this logically led to this avenue of inquiry in autistic people. Studies addressing a deficiency in perception of bodily feedback and the reduced capacity to integrate the information are ongoing.
When I think of interoceptors and exteroceptors, two things come to mind immediately. Fascia and skin. When I think of fascia, I think of full body movements charged with spring and recoil. Enter brachiation. Suspending a body from a single upper limb utilizes long stretches of mysofascial continuum simultaneously. Looking at hanging from a single upper limb from a muscular standpoint, attention immediately lands on latissiumus dorsi. Recent work demonstrates that the latissimus is functionally and structurally attached to the opposite glutes (Calvalhais et al) and lower limb (Vleeming et al) through the thoracolumbar fascia. The arm is linked to this same continuum of tissue when the limb is overhead (Myers) creating one long chain. The latissimus has been described as essential to shoulder and pelvic stability, both of which are essential to diaphragmatic action and breathing. The fascia is full of receptors and contains 10x as many interoceptors as other tissues of the body. Those receptors are hard-wired into the nervous system influencing its capacity to set global and local tone throughout the myofascial continuum. The diaphragm is also full of interoceptors, and the breath is tied to systemic neuroendocrine regulation and systemic allostasis, the processes by which the body responds to stressors in order to regain homeostasis. The mechanisms of systemic allostasis includes the HPA axis (hypothalamic-pituitary-adrenal axis, a neuroendocrine system that regulates stress, mood, emotions, and body processes), pain perception, and executive functioning (McEwen).
While the literature does not have a lot of information pertaining to brachiation and suspension precisely, it does speak to the effects of similar stimuli from different types of manual therapy that utilize joint distraction, tissue shear, vibration, touch, pressure, etc, and their effects on receptors that elicit peripheral, spinal, and supraspinal changes (Bialosky et al). Past work involving joint mobilizations has shown that distraction, rotation, and cyclical motions provide calming stimuli to the nervous system. Activation of mechanoreceptors in joint capsules, muscle, and the skin bombard the nervous system with input that has been shown to abate nociception and to decrease muscle guarding.
Anthropological literature on arboreal locomotion reveals true brachiators utilize pendular movements that continually exchange potential and kinetic energy for optimal efficiency (Michilsens et al). This would appear to be descriptive of the tension and recoil of fascial chains in action. Brachiation is basically full body cyclical and rotational distraction with loading and unloading of myofascial continuums. It is a movement full of the nervous system’s favorite things.
All of this boils down to the potential capacity for brachiation to be a robust stimulus to both the nervous and neuroendocrine systems. Perhaps this proprioceptive bombardment and its subsequent physiological adjustments could produce a very centering, calming, and organizing down-regulation of a body subjected to stressful circumstances. This train of thought suggests that applications of different types of movement patterns may have implications that go well beyond the ways that we generally think of them.
Similarities in structure between modern day full-time brachiators (i.e. Gibbon monkeys) and present-day humans include long curved fingers, reduced thumbs, long forelimbs, freely rotating wrists, flexible shoulders, and good grasping capabilities (Jurmain et al). Gutierrez informs us that clavicles are struts in brachiators that position the upper limb away from the body to free up global positioning and use of the limb overhead while increasing the limb’s strength and dexterity. It is clear that our ancestors spent some time hanging out at height as it is written all over our bodies.
However, there seems to be a great deal of controversy and discussion in the zoology literature regarding why and when it was that our ancestors decided to stand upright, and ultimately why they decided to stay that way. Recent findings in the fossil record are more supportive of the notion that our more direct ancestors were not strictly arboreal folk brachiating from one limb to the next, but rather generalists who did some brachiating, did some climbing, and were quadruped in a swing through kind of way (knuckle-walking) before they were biped (a “semiterrestrial ecological generalist” for those keeping score) (Niemitz). There is discussion of brachiation as an exaptation, or a pre-adaptation, to becoming bipedal. An exaptation is a trait that can serve one function and come to serve another over time. This line of thought suggests that brachiating gave us the capacity to become bipedal by promoting upright posture and situating the thorax over the pelvis with stability and control.
For better or worse, human beings are found all over the planet. One of the features of humans that makes us so resilient is that we are not particularly well adapted to anything. Therefore, we not confined to a small temperature zone, particular climate, or single food source. We are largely able to support ourselves with a source of water, edibles, and an appropriate oxygen percentage. What we lack in less supportive environments we are able to make up for with the craftiness of our relatively enlarged brains and opposable thumbs. Our great adaptability comes from our great capacity to be generalists – just like our ancestors who could get food from the trees, the side of cliffs, and eventually wade upright through marshes and shorelines, scrounge around the savannahs, and run across the plains.
“You‘re gonna get better or you‘re gonna get worse, but you‘re not gonna stay the same.” – JP The body always changes in response to stimulus, and physical activity is a boss stimulus. Evolution never stops. It is going on right now. And while we are sharpening our survival knives in some areas (i.e. Uber app, SmartWool, and FreshDirect), we are actually losing capacity in others. Physical devolution is being driven by increasingly sedentary lifestyles, screen time, and comfortable chairs. We are shrinking to the size of the bowls we find ourselves in most frequently, and this means we are becoming more specialized and less generalized as our posture, mobility, strength, and stability cease to be sufficient to climb, hang, swing, squat, and even get off the floor.
Much like a deep squat is a presentation of end range hip, knee, and ankle mobility, and the motor control to hold everything together, brachiation is the presentation of end range shoulder, scapular, and thoracic spine mobility, upper quarter rotational capacity, and the motor control to hold it all together through full body reciprocal motion. One is a full body compression, and the other is a full body distraction. Both represent the ability of the limbs to support the weight of the body. We need them both to remain solid generalists capable of escaping oncoming trains and high water. The exaptation capacities of brachiating – the upright posture, stable diaphragm and pelvis, elongated legs, full mobility of the upper quarters, and resilience of the myofascial continuum – are needed to keep our bodies healthy, agile, and resilient. It is accepted that every push demands a pull, and every straight plane motion demands a rotation. Perhaps every compression also demands a distraction.