-By Kaitlyn Patterson, Team Athletic Mentors cyclist
I’ve been intrigued by the endocrine system and nervous system for quite a while and after the grand tour of the major medical fields over my second and now third year of medical school, they continue to be my favorites. They are dynamic and responsive, influencing our eating patterns, sleep, body composition, happiness and performance. The endocrine system works through pulses of hormones – growth hormones, stress hormones, insulin – all with different patterns but always dynamic. In fact, the hallmark of a dysfunctional endocrine system is a stagnant or non-responsive hormone. The nervous system is also constantly changing- toggling between different modes: the sympathetic, commonly referred to as “fight or flight” and parasympathetic or “rest and digest.” Similarly, there should be a cycle to this as well since either one isn’t meant to be always on. The nervous and endocrine system work together to make sure your physiology matches whatever situation you happen to be in. Quite impressive really.
One of the themes I have been struck by during my clinical training is the number of medical problems associated with chronic stimulation of the sympathetic nervous system. Most of these are common chronic diseases- sleep apnea, COPD, congestive heart failure, type II diabetes. It is an appropriate response by the nervous system as it is answering to a real threat- be it a lack of adequate oxygen entering the lungs, episodes where breathing stops, or a heart not pumping adequately. However, the constant activation of the sympathetic nervous system eventually creates its own problems- including reduced sensitivity to hormones like insulin and even depression. A sustained stress response is actually one of the possible mechanisms of the high rate of depression after heart attacks or strokes.
As athletes, we depend on our sympathetic nervous system every time we jump on the bike, in the pool or lace up the running shoes. It helps orchestrate the physiological response to exercise to allow us to do physical feats, feel good doing it and induce health benefits. As long as the stressor is episodic and followed by a shift to parasympathetic (recovery) mode for a time, all is good. However, it can be all too easy to abuse the sympathetic nervous system. Whether it be becoming greedy about training volume or intensity, additional life stress, lack of sleep, or under-fueling, sometimes the balance can be tipped into spending too much time in “fight or flight” mode.
At first, this is not obvious and we can get away with asking a lot of our sympathetic nervous system and even feel good doing it. However, it is ultimately unsustainable and can create the same type of maladaptive changes as seen in chronic diseases discussed earlier. Although performance might not decline initially, the first signs can include waking up too early and not being able to fall back asleep, feeling irritable, hungry, or losing motivation to train. If it continues it essentially can create a state of nervous system exhaustion when performance is significantly impaired. This spectrum is often referred to as “overtraining syndrome” although it is still a poorly understood phenomenon.
I personally believe this process is what many people refer to as “burnout.” Burnout is a bit of a buzzword especially in medicine right now, but it is often used as an ambiguous term. However, it appears there are parallels between athletic and professional burnout and both consistent with a maladaptive stress response with a big factor being the constant sympathetic nervous system stimulation.
I am guilty of phases of nervous system abuse, but feel I have gotten better at both identifying and respecting it. One hurdle for me is admitting I’m tired (even if I don’t think I “deserve” to be) and actually resting in response. For me and probably many endurance athletes, resting can take more discipline than training and it can initially be difficult to trust that resting more can lead to going faster and feeling better. Although race results are not everything, still being able to perform well while training less provides positive reinforcement. This process requires constant attention and I think it is one of the biggest challenges of being an athlete and a future physician.
Although a constant vigilance for this phenomenon is important for athletes and people in high pressure careers such as medicine, this is an important awareness for everyone. Unfortunately, the society we live in does not necessarily have built in cycles of rest and recovery. I think everyone should be aware of the need for natural ebbs and flows and the importance of respecting and protecting our nervous systems, not just to be good athletes or professionals, but to be healthy, fulfilled people.