One of the best functions of yoga is its effect on our central nervous system. Learning how to relax, which is the focus of relaxation yoga in particular, helps our nervous system to return to its resting state.
The central nervous system (CNS; which consists of the brain and spinal cord) is autonomic. This means that it operates outside of our conscious control. However, our conscious input (thoughts and emotions) has a significant influence on it. And vice versa: the state of our CNS affects how we feel and how we think. This is one of the keys to how relaxation yoga works.
Our CNS is regulated by two complementary systems - the parasympathetic (PNS) and the sympathetic (SNS) systems. Both systems are always active and when they are in balance they keep our body functions in a state of balance. The sympathetic system is easy to remember: "flight or fight." We evolved an emergency system to help us survive a sudden perceived threat, like a big dog growling at us.
The hippocampus in the brain rings the alarm bell, sending off a variety of nervous impulses and a cascade of neurotransmitters and hormones. This warning blast immediately diverts our body resources to deal with an emergency. It stimulates the adrenal glands above our kidneys to release adrenaline and cortisol into our blood.
Our breathing rate increases, our blood pressure goes up, the bronchioles in our lungs dilate, our liver releases glucose into our bloodstream, our muscles tense to protect themselves from potential injury, we start sweating and our pupils dilate to help us see better.
Meanwhile, peristalsis in our intestines decreases, our mouths go dry, and a wide variety of restorative processes in our body temporarily take a back seat, such as cell division, cellular waste removal and immune processes.
The parasympathetic system is our "rest and digest" or "feed and breed" system. When our body is at rest, all of our restorative functions kick into gear. Regular day-to-day cellular functions resume. We eat, sleep, recover from physical activity, we fight infections and disease, and, yes, perhaps we enjoy a little romp when the opportunity arises.
At the cellular level, our cells are busy performing their assigned metabolic jobs. They grow and divide, repair DNA, remove waste products, break down and remove dead cells, build tissues and so on. Our immune system is at work repairing injuries and patrolling our blood stream for invaders. Our neurons repair any damage and build new connections. We make hormones, digest food, and feed our cells.
When the SNS and PNS are in balance, our bodies are incredible machines! When they are not, we have a problem. Most often this comes in the form of a chronically activated sympathetic nervous system (SNS). This imbalance often results from long-term stress. Some knowledge about how our CNS works and having some relaxation skills under our belts can give us a significant edge during training.
First, let's map out how our CNS ebbs and flows over a typical day, and it does so significantly. In deep sleep, around 2 to 4 am, our SNS is at its most inactive level. Our brains are busy making new connections and removing waste molecules. Our skeletal muscles are disengaged from our brains, and while we are essentially paralyzed, our muscle cells are repairing all the cellular damage and micro-tears that occurred during the previous day's workout. Excess lactic acid is being removed and glucose is being stored up. The cells are busily dividing, creating new muscle tissue. Our bones are busy making new bone cells. About an hour before we wake up, our SNS starts to rev up a little bit, increasing our breathing rate, alerting our brain to wake us up. On the way to the gym, our mind signals to our body that we are going to work out. Like Pavlov's dog, our heart rate increases in anticipation. Once there, we get our sweat on. Early morning is a great time to work out because it fits in beautifully with our natural circadian rhythm. Our SNS activity naturally peaks early in the morning. After workout, we have a nutritious breakfast. The process of eating as well as food in our stomach triggers our PNS. Our body sequesters those adrenaline-type hormones from our blood stream and we return to a resting state. Having seen our friends, having a laugh or two and having accomplished something are additional emotional signals to our bodies to relax and rest. By around bedtime, after a good supper, our bodies should be naturally starting to gear down into sleepiness as SNS activity further quiets down.
When it all works smoothly, this is a fantastic long-term plan that keeps our bodies (and minds) in balance, or homeostasis. It helps us build healthy tissue and fight disease. It has even been shown to keep our cellular telomeres longer. This is technical jargon that means our individual cells act like they are younger and they can divide more times before they die. I think you can see where I'm going here. This is a recipe for optimal training.
Homeostasis gets bumped off kilter when we experience a big life stress, but there is not much we can do but allow ourselves heal. The more insidious and more dangerous situation for our health is chronic low-level stress. This is the kind of stress we may not even know we have. It can build up from our day-to-day work environment, money stress, family life, a too-long honey-do list, a too busy schedule, and even just an attitude that we must attack our entire day in full-on warrior mode. It is all too easy to forget that we need comfort and rest, as well, EVERY DAY. Modern life all by itself, I think, is enough to get us out of whack.
And when we're out of whack, our adrenaline and cortisol levels don't drop down to rest level during the day after our workout. Our bodies handle short-term elevations, such as during a workout or a temporary upset, very well. We evolved for that. However, our bodies don't handle long-term elevated stress levels well at all. A chronically stimulated SNS wrecks havoc on our bodily systems. Our muscles don't have a chance to repair and rebuild. We don't digest our food well and we don't get the nutrients we need to restore our bodies. Our immune system doesn't function optimally, leaving us easier prey to flu and colds and possibly even at least some kinds of cancer, although that scientific link is weak. Our blood has too much glucose in it, which can lead to diabetes. Our blood pressure stays high and does its own damage to our arteries and heart. We don't sleep well, and this means our brain doesn't have a chance to restore and repair. The resting tone in our muscles is high throughout the day, and that puts extra stress on connective tissues such as ligaments and tendons. This is a recipe for poor training performance, and ultimately it can lead to over-training and a reduction in performance. Often when we notice a lack of progress, it's natural to stress out about that and train even harder, leading to a downward spiral. Everything we work at so hard in the gym is undone by our out-of-balance CNS. When we find ourselves in this frustrating situation, it might be good practise to first take a metal check on where we are at.
It is very difficult to know when our body is under chronic stress. We don't directly "feel" an overactive SNS. What we do feel are symptoms and we can watch out for them: headaches, racing and/or circular thoughts, feelings of anxiety, restlessness, feeling overwhelmed, irritability, trouble getting to sleep, trouble staying asleep, a tight-feeling chest, feeling rigid, drinking too much after work are all signals to reduce stress. We can't will it down, in the same way that we can't will ourselves to sleep when we've got insomnia. However, ust knowing how our system works and how important rest is puts us on the right track. When you find yourself thinking you don't have time for that relaxing . . . pause for a second thought. Keep life simple as you can while you're in serious training mode, rest often and deeply, eat well.
And now back to the bullet point in my title: Relaxation yoga is one ingredient can rebalance our CNS. In these kinds of classes we learn to use our minds and our bodies to slow our breathing rate down. Different kinds of yoga also use various poses and movements to facilitate relaxation. A slowing of breath and a deepening of breath sends an unconscious signal to our CNS to calm itself and shift toward the PNS side of the spectrum. There are lots of relaxing yoga routines available to experiment with. Meditation is another practise that allows our nervous system to find its way back into balance. These ancient practises are enjoyable to learn and they are generally safe.