What is the purpose of the 12 second all-out burst during the cardio sessions? This isn’t long enough to be considered interval training, so to explain why it is essential you need to learn a little about the nervous system.
Your nervous system can be divided into the somatic nervous system which controls voluntary movement and the autonomic nervous system which is responsible for everything that happens automatically, such as breathing, digestion, and heart beat. The autonomic nervous system can be further divided into the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS).
The SNS is externally facing and is responsible for bringing energy and fuel to the muscles. This is the part of the nervous system that is responsible for the “fight or flight” reaction to stress. When the SNS perceives a stressor heart rate increases, glucose is released into the blood stream, digestion slows and cortisol is released by the adrenal glands. All of these things give your body the energy to face danger.
The PNS should be the default setting for your autonomic nervous system. When the PNS is in charge your body is building itself up. The PNS is responsible for “rest and digest” so when it is in control your heart rate and respiration slow, your blood pressure decreases, stress hormones are decreased and blood flow is redirected to the digestive system. The more time you spend with the PNS in charge the healthier you will be.
Both parts of the autonomic nervous system are necessary for survival and it is important to maintain a balance between the two. Unfortunately, your body can’t tell the difference between real and imagined stress. Chronic stress activates the SNS and pretty soon your PNS is under active and you are in a constant state of heightened awareness, increased blood pressure, heart rate, respiration, blood glucose and cortisol levels. We need to teach the PNS to activate and promote recovery.
Our primitive ancestors lived in a state of balance between the SNS and PNS. Most of their time was spent with the PNS in charge, and when they were threatened by danger (like being chased by a bear) the SNS took over. The time spent with the SNS in charge was relatively short, they either escaped danger or died. Nowadays most people under a constant state of stress and the body responds by having the SNS constantly activated. We need to teach our PNS to take over, and that is what the 12 second burst is all about.
By putting the body a low load of stress (the cardio exercise) and then adding a high amount of stress for a short period we can force the PNS to take over. After you finish the burst you will actually feel your PNS kick in and start to calm your body while you continue to do a low level of cardio. This helps to teach your PNS to take over even while some stressors are present, and the SNS to only respond to heavier stressors.
By consistently practicing short periods of a controlled heavy stress load you can teach your body not to respond to low level stresses with a “flight or flight” reaction by the SNS. The PNS becomes our default setting, reducing our cortisol level and blood pressure, improving immune function and sleep, reducing insulin resistance and leading to a healthier lifestyle!