Wednesday, November 8, 2017

Stuff I Learned - Isometric Contraction

Perhaps you remember Hans and Franz of Saturday Night Live? They were keenly interested in pumping you up, and demonstrated the results of their workout regimen at the slightest provocation.

Hans and Franz want to pump you up. You can see the
results as they contract muscles isometrically.
Posing like Hans, Franz or California's former Governor, Arnold Schwarzenegger, involves isometric muscle contraction. When you make a muscle, you're contracting your muscles isometrically. While Yoga tends to de-emphasize bulking up with muscle mass, most yoga poses also involve isometric muscle contraction.

Isometric muscle contraction is different than dynamic muscle contraction in some significant ways. One key difference between dynamic muscle contraction (found in common activities like walking, running or biking) and static muscle contraction is the rate of blood flow to the working muscle. In dynamic muscle contraction, the blood flow to the working muscle increases. In static, or isometric, muscle contraction, the blood flow to the working muscle decreases.

When muscles are working, they need more nutrients in order to maintain their activity. With dynamic contraction, the blood flow to the muscle increases. In isometric contraction, on the other hand, blood flow actually decreases. Why does the blood flow decrease in isometric contraction at just the time that the muscles are needing more blood supply? Because the static contraction of the muscle presses so hard on the blood vessels that the blood supply is impeded. With sufficient isometric contraction (effort), the blood supply to the working muscle may actually be shut off.

When working muscles are not receiving the blood that they need to continue working, receptors in the working muscle send a signal to the brain - more blood, right now! The cardiovascular control centers of the brain then generate greater activation of the sympathetic nervous system, which both raises heart rate and blood pressure.

Put another way - holding isometric contraction may catalyze a fight, flight, freeze response. Now, don't worry - this is not to suggest that holding yoga poses is a stressor. Far from it - I think many of us have experienced the relaxing benefits of a satisfying yoga practice.

If isometric contraction (holding poses) may cause greater sympathetic activation, how does Yoga work? One theory is that the relaxation at the end of a session allows your central nervous system to overcorrect after having modestly upregulated due to the various Yoga techniques. It's thought that holding poses may cause sympathetic activation, and resting in Savasana at the end of class gives your system the time and space to overcorrect into a state of greater relaxation.

In the past few years, I've seen more teachers shorten or even eliminate the relaxation at the end of class. Even though many people are busy and it can seem like a waste of time to lie still, in many respects, I think Savasana may be the most important yoga pose. If you aren't getting a chance for your autonomic nervous system to reset at the end of your class or practice, I encourage you to take that extra 5-10 minutes to do so.

Sunday, October 29, 2017

Stuff I Learned - Circulatory System

When I was a kid, my family drove a ginormous Ford van. True to the times, it was fully customized with the requisite shag carpeting, wood paneling and captain's chairs. Sweet.

In addition to feeling like a rolling living room, it had two huge fuel tanks. Each tank was probably about as big as my entire Smart Car, and the range of the Econoline was remarkably long. It felt like refueling took the better part of the day, though I scarcely remember ever stopping for gas in that van. I have fond late-70's memories of road trips to my family's cabin, track meets, and ski trips in that van - mostly accomplished without having to stop to refuel.

Pedestrians - get out of the way!
Small window made it hard to see
out of groovy vans.
Why am I reminiscing about the van that caused global warming? I'm mentioning this van because it had a large capacity to carry fluid, and it did so by having more than one reservoir to handle all its capacity. The human body similarly has a lot of fluid to carry around - in the body's case, the fluid I'm referencing is blood.

Circulating blood is necessary for life, and the body is engineered with lots of blood capacity. Copious blood capacity is a good thing, as having just enough blood to get by would mean that even a small wound and blood loss would be fatal. Evolutionary pressures favored the creatures that had extra blood carrying capacity, and we now walk around with reservoirs of blood that are carried in different tanks in our bodies.

One of the tanks carrying our extra blood capacity are the abdominal organs (splanchnic region). As you're reading this blog, there are likely at least a few pints of blood sloshing around in your body that are not actively involved in maintaining your life. They're in reserve, waiting to perfuse tissues, as needed.

This blood capacity isn't just for protecting against blood loss. When you exercise, this extra blood capacity is also very useful. Exercising muscles require lots of nutrients and oxygen, and it's the blood that carries these substances to the muscles. In addition, exercising muscles release lots of waste by-products that need to be carried away from from the action. While the body has a lot of blood capacity, the working muscles have a huge appetite for blood, and there is not enough blood to supply every tissue all at once.

The body's response is clever - during exercise, blood supply is directed to the working muscles, and away from areas that are less important in supporting the activity. Your body automatically reapportions blood away from lower-priority tasks and toward higher-priority tasks.

After I finish writing this blog, for example, I'm planning to head out to Blue Mound State Park for an ~8-mile trail run. During that run, my legs will require a lot of blood - some of the major muscles will require to the tune of 3-5 liters of blood flow per minute. That's a lot of blood, and that rate of consumption would even exhaust the volumetric carrying capacity of the 1977 Econoline van!

My body will make some interesting adaptations to accommodate this activity. Once I decide to begin running, my brain stem will signal my sympathetic nervous system to initiate a modest fight/flight/freeze response. This sympathetic activation will increase my heart rate and constrict the blood vessels throughout my body. In the first minutes of my run, my rest and digest response will diminish, and my heart rate will rapidly increase due to this parasympathetic withdrawal.

This blog isn't really about vans, though I now have vans on my mind.
From ages 16 - 35, I primarily drove VW vans.
As the exercise continues, metaboreceptors in my muscles will sense accumulating waste byproducts, and will send signals to my brainstem requesting greater blood flow. My body will respond by opening up the floodgates of blood flow to the working muscles, while further restricting blood flow to any muscles that aren't working. In addition to redirecting blood flow away from non-working muscles and toward working muscles, my body will more or less shut down my GI tract, and divert the huge amount of blood in the splanchnic reservoir toward my working muscles.

In the 1977 Econoline van, a switch on the dashboard shifted fuel supply from one tank to the other tank. In the human body, the shifting of blood flow occurs automatically. During this morning's run, I will not need to focus on or visualize redirecting blood flow  - it happens organically thanks to the vast intelligence that infuses the human body.

When I run, I try to reduce the degree to which I control my movements. Most of my conscious awareness of running is just that - awareness. I practice feeling my feet contacting the ground, sensing the movement of prana/breath, and enjoying the unfolding scenery that surrounds me. Particularly for those of us who have embraced movement practices, it can be tempting to micromanage movement experiences.

This micromanaging can take various forms, though the most common forms are holding the body in the right way, and/or controlling breathing.  As I've mentioned in previous blog entries, I encourage you to resist the temptation to use movement practices as a means to reinforce controlling tendencies, and use movement and movement practices to connect with the vast intelligence that pervades the human body.

Have a great week!


Friday, October 20, 2017

Keep an eye out for the Helpers

The other night I had just cleaned up after dinner, and was settling down with Buddy Cat to go over notes from last week's Exercise Physiology lecture. In my final lead-up procrastination (procrastination takes many forms), I flipped to The Last Word column in the The Week magazine, and found a loving tribute to Mr. Rogers.

Mr. Rogers and Daniel Striped Tiger
As I read the article, I grew misty-eyed thinking about the kindness that Mr. Rogers seemed to embody. As Anthony Breznican described his chance encounter with Fred Rogers, I was transported back to the magical world of Mr. Roger's Neighborhood. His neighborhood was filled with kindness and appreciation - basic goodness.

Each day we have many opportunities to embody kindness and appreciation for the myriad beings that surround us. May we enjoy every opportunity to be the kind of helper that Mr. Rogers speaks of.

Have a great week,


Thursday, October 12, 2017

Stuff I Learned - ANS

For years, the book The Anatomy of Hatha Yoga sat on my bed stand, and I cannot estimate how many times I read and reread this classic text. In this and other readings, I came to appreciate yoga's influence on the Autonomic Nervous System (ANS), and in particular its potential to shift our response mode from a potentially inappropriate fight/flight/freeze response to a more sustainable rest and digest default status.
The human heart beats at about 100 bpm,
even if disconnected from
neural input.
Among the organs that are influenced by the ANS is the heart and its rate. Heart rate is naturally set to about 100 beats per minute (bpm) by pacemaker cells in the heart. In the absence of ANS input, your heart naturally beats at about 100 bpm. Provided sufficient nutrition, the human heart continues to beat at this steady drum beat even when outside of the body and disconnected from the brain or any other neural input. (please, do not try this at home.)

Your ANS regulates your
heart rate.

While 100 bpm is a pretty functional default heart rate, it's too slow to sufficiently supply blood to your brain and working muscles during exercise, and faster than is necessary to supply your tissues with blood while you're resting. Here's where the brilliance of the body shines forth; your ANS modulates your heart rate to match the needs of your tissues. The rest and digest (parasympathetic) aspect of your ANS acts to lower your heart rate while you're resting. In the adjacent diagram, the shaded portion labelled vagus represents the parasympathetic activation that actively lowers your heart rate while you're resting. The fight/flight/freeze (sympathetic) aspect of your ANS raises your heart rate while you're active or otherwise aroused.

What does this mean for those of us that are living in bodies? Both the sympathetic and parasympathetic aspects of your ANS are essential for optimal health. It can be easy to misinterpret discussions of the ANS and conclude that
  • sympathetic = bad
  • parasympathetic = good
Unfortunately, this simplification is incorrect. What's bad about sympathetic response is not its existence, but the chronicity of its overactivity in our 21st century lives. We need the heart rate to rise when we're active, and it's also vitally important that we have the capacity to relax. Thankfully, regular exercise and contemplative practices like Yoga have the potential to facilitate optimal regulation of the ANS.

In the interest of mental and physical health, are you taking some time each week for physical activity?

Saturday, October 7, 2017

Back Post-Mortem

My back used to go out regularly. As many of you have probably also experienced, back events make verticality difficult, and activities such as rolling over in bed and sneezing become major hurdles. I was probably about 13 or 14 years old when I first experienced back pain, and ever since I've episodically been reminded of samsara's suffering.

The last time that my back went out was in November of 2014. I remember that event clearly, as I was scheduled to teach an out-of-town yoga workshop the following weekend. I could barely stand up without assistance, though rescheduling the workshop wasn't really feasible. With some Aleve and adrenaline coursing through my bloodstream, I traveled, taught, and wasn't that much worse for the wear.

While my back started hurting shortly after the
eclipse, I'm disinclined to think they're related.
Since then, I redoubled my focus on Pilates, and I've enjoyed one of the longest stretches of a strong back since I was a kid. After 2+ years without an episode, I was starting to think that I'd finally licked my sacral-iliac (SI) joint instability.

Alas, samsara is still wrought with suffering! At the very beginning of this school year, my back went out. It was not the worst episode I've experienced - far from it. I couldn't stand up very straight for a few days, and I moved around the house like I had suddenly aged a few decades, though I was still able to execute life's tasks without too much assistance. Thankfully I've learned a few things about managing my back; avoid stretching the tight muscles, take anti-inflammatory meds and resist the temptation to realign my SI joint or lumbar spine by cracking anything.

While it's always tempting to find the cause of a life event, in my experience causality is often more nuanced and multi-faceted than the one thing. After reflecting on the lead-up to this incident, I've identified three factors that I think contributed to the most recent episode.
  • Last Summer I felt so good that I ran outdoors at every opportunity. Staying inside and working on the Pilates equipment or doing a mat workout didn't seem as compelling as running in the Arb or Blue Mound State Park. As a result, I neglected to keep up on the core work that was allowing me to feel so good!
  • My gait mechanics were disturbed after a minor foot injury. As I often teach in therapeutic Yoga and Pilates sessions, a minor shift in gait can transfer stress into the lower-back. Eight miles into a late-Summer twelve mile trail run, I tripped over a root. Ever since, I have been slightly favoring my right foot. I don't think this compensation was sufficient to cause my back to go out, though I think the slight stress on my back compounded the other contributors.
  • Stress. When I teach Yoga and Pilates, I almost always find that people experience lower-back episodes during stressful times. Alas, I was feeling stressed about the upcoming school year and my heavier-than-usual course load.
By themselves, none of these stressors were all that significant; taken together, I think they were sufficient to remind me to practice the things that I teach.

I'm now back into the rhythm of the school year, and happily vertical, again!

Sunday, October 1, 2017

Stuff I Learned - Autism as Movement Disorder?

Being in graduate school allows me to wear many hats. One of the hats is that of teacher; to the undergrads in the anatomy course that I TA, I'm one of the teaching staff. Another hat is that of student; I'm still deep in the throes of taking coursework, with the full repertoire of exams, presentations and papers. And as graduate school progresses, my biggest hat will ultimately become that of researcher.

While I'm just starting to dip my toes into the role of researcher, I'm already learning a lot about the cutting edge research in my various areas of interest.
This fellow is wearing a very large hat.

As many of you know, I've long been interested in Autism Spectrum Disorder (ASD). The non-profit that I helped to found, YogAutism, sprung from my initial forays into bringing the benefits of Yoga to those with ASD. Now that I'm choosing a research focus, one of my interests is building on the research that began with YogAutism.

ASD is generally defined by challenges with social interaction, though it's becoming clearer that a retinue of movement disorders also accompany the ASD diagnosis. Some researchers have gone so far as to suggest that ASD is primarily a movement disorder, with social challenges riding on the proverbial coattails of the disordered movement patterns.

I think it's too soon for us to reframe ASD as primarily a movement disorder, though I do think it may be fruitful to consider how movement practices may reduce the challenges of living with ASD. If particular patterns of brain connectivity correlate with the movement and social challenges of ASD, is it too great a leap to consider how movement practices may help rewire (neuroplasticity) the brain? These are the sorts of research questions that I'm starting to ask, and I'm grateful for the opportunity to rigorously explore these questions at the University of Wisconsin - Madison!

Before I sign off for this week, I'm going to drift into potentially polarizing terrain:

"Motor deficits may be present even before communicative or social deficits." (Fournier, et al. Motor Coordination in Autism Spectrum Disorders: A Synthesis and Meta-Analysis, 2010).  I'm very interested in the emerging evidence suggesting that the movement deficits of ASD predate the ASD diagnosis that's based on communication or social deficits. Put another way - the child that was completely normal before _____________ , may well have had ASD -related anomalies in their gait and/or eye tracking that existed well before the event that caused ASD.

That's all for this now - may your week be rewarding!

Sunday, September 17, 2017

Stuff I Learned - Getting out of Bed

In the first week of my Exercise Physiology course we studied how the circulatory system responds to changes in position, particularly in the transition from supine to standing. If you're anything like me, you may consider studying getting out of bed about as interesting as sodden cardboard. Interestingly, it turns out that this seemingly simple transition involves numerous adaptations that are unique to the human organism.

One of the problems with our human-ness involves rearing up on our hind legs. OK - so being a biped isn't necessarily a problem, though the vertical orientation creates some serious design challenges. Our brains are at the top of our vertical bodies, which means that gravity is constantly pulling blood away from our brains. Brains are very hungry consumers of blood (much like zombies are hungry consumers of brains) and if the brain doesn't get a sufficient blood supply, you will quickly pass out.
Buddy Cat has 70% of his blood above his heart. Like any quadruped, this means that getting blood to the brain isn't all that difficult - the blood is already above the heart and is pretty close to the brain. Humans, on the other hand, have 70% of their blood below their hearts. This means that our hearts have to work hard to pump the blood uphill into the brain. 

When you move from supine to standing, you're at risk of game-over. What keeps us (mostly) from passing out when standing up? It's actually a series of adaptations that facilitates this seemingly simple transition.
  • Your rest and digest (parasympathetic) nervous system lowers your heart rate while you're resting. Upon standing, the parasympathetic nervous system stops lowering your heart rate, and your heart rate increases quite a bit in what's called parasympathetic withdrawal. For a few moments, your faster heart beat will help pump blood uphill to your brain.
  • Unfortunately, the heart can only pump what it receives, and when you first stand up most of the blood remains stuck in the floppy veins of the legs. Thankfully, your body has the capacity to "tighten" the veins (vasoconstriction) to help facilitate the flow of blood upward into the brain. Upon standing, vasoconstriction helps move the blood out of your legs and up into your torso.
  • In moving from supine to standing, you use muscles in your legs to accomplish that transition. The contracting muscles squeeze the veins, which further helps to push the blood upstream and into your brain.
  • The muscle pump is accompanied by the respiratory pump. (I wrote about the respiratory pump in an earlier blog posting.) When you inhale, the pressure in your thoracic cavity is reduced, which tends to pull blood uphill and into your heart. When you exhale, the pressure in your thoracic cavity increases, which tends to push the blood out of your heart. The respiratory pump also helps to improve circulation to the brain.
  • In your abdominal cavity, organs also help in this process of moving blood. For example, your liver is capable of storing a significant amount of blood volume. Related to the respiratory pump, when you breathe, blood that's stored in the liver is lifted upward into active circulation.
These are just a few of the adaptations that are unique to the human animal. I'm just getting back into the rhythm of the new school year, so I'll keep this first blog posting brief and to-the-point. I look forward to learning more and sharing more about this wondrous vehicle that we each inhabit.

'Til next week!