The Nervous System consist of three major parts: the central nervous system (CNS), peripheral nervous system (PNS), and autonomic nervous system (ANS). Each system is a complex collection of nerves and neurons that transmit signals between different parts of the body. It's basically the body's electrical wiring.
The part of the nervous system that is most important to us is the autonomic nervous system, which helps appropriately power all our internal organs based on the information it receives about the body's state and the external environment surrounding it. Some of the body's functions the ANS controls include:
- Blood pressure
- Heart and Breathing Rate
- Body Temperature
- Balance of Water and electrolytes
The ANS has two main divisions: the sympathetic nervous system and the parasympathetic nervous system. The Sympathetic Nervous System responds by stimulating many of the above functions to prepare the body for stressful or emergency situations by performing actions such as:
- Increasing heart rate
- Dilating airways and pupils
- Increasing sweat
- Releasing stored energy
- Slowing process like digestion and urination
This is why our sympathetic nervous system is often called our "fight-or-flight" system. The Parasympathetic Nervous System, on the other hand, is known as our "rest-and-digest" system. It's responsible for down-regulating those functions to bring the body back to homeostasis. Examples include:
- Slowing heart rate
- Decreasing blood pressure
- Stimulating digestion
- Relaxing muscles and increasing energy storage
Why Does This Matter?
To maximize training adaptations, you need to take advantage of the effects of both the sympathetic and parasympathetic nervous system.
The parasympathetic nervous system is most beneficial to us because it is the state we ideally want to be in the vast majority of time. This is the state our body recovers in most efficiently due to the relaxed state and increased absorption/digestion of nutrients.
Engaging the parasympathetic nervous system can also be very beneficial in your daily training routine, particularly during cool-downs after training, as this can shift your body immediately into a recovery state. Diaphragmatic breathing is one of the simplest and most convenient ways to stimulate the relaxation response of your parasympathetic nervous system. It would also be highly beneficial for individuals who tend to burn out early in workouts to come into a training session in a parasympathetic state.
Inducing the effects of the sympathetic nervous system for its benefits also has its time and place. Specifically, before an important session in a strength cycle or one where you will be attempting a new personal record for a lift. Everyone knows the weight feels lighter when you'er surrounded by your yelling training partners while the music is blasting. This environment ignites our SNS, giving us tunnel vision and causing short/shallowing breathing as we brace for the big lift.
Although it feels great to hit those PRs, relying on the SNS for prolonged periods of time can lead to burnout/overtraining. This is due to the higher level of cortisol release and fatigue build-up it causes. A perfect example of this burnout is seen in many young athletes who just start lifting weights. They think it is the best thing ever, they don't take rest days, and they go 100% every session. Pretty soon, they find themselves either extremely rundown or injured. The truth is the vast majority of humans spend too much time in that "fight-or-flight" state due to things like constant stress, poor posture and bad lifestyle habits.
That's why it is ideal to only rely on the SNS sparingly, such as when you have a very important training session or competition. This approach will lead to steady improvement over long periods of time versus large improvements initially that plateau quickly and are often followed up by declines. In a future piece, I'll detail tactics for stimulating the parasympathetic and sympathetic nervous systems that you can use to gain greater control of your body and mind.
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