Parasympathetic Overtraining and the Endurance Athlete-

"Why can't I get my heart rate up to its usual rate on my run or ride?" "Why is my heart rate so much lower than usual when I work out?" Scour the internet, try to find why you can't perform a given workout at your usual heart rate, and you will almost definitely be misled. The form of overtraining most endurance athletes are most susceptible to is rarely discussed. In turn, a form of overtraining with completely opposing signs and symptoms is discussed. This drives endurance athletes whom are overtrained or on the verge of being overtrained to keep on digging that dangerous hole which is overtraining, and prevents them from reaching their potential.

Several years ago I began to research the topic of overtraining in endurance athletes. It confounded me that even in mainstream publications focusing on runners and triathletes, i.e. endurance athletes, the information being published was not relevant to our particular situation as endurance athletes. The majority of published information readily available discussed only one of the two types of overtraining. Most of these articles wholly ignored and failed to mention that overtraining comes in two forms; Sympathetic and Parasympathetic. In only discussing the type of overtraining known as Sympathetic, endurance athletes have been misinformed entirely of what overtraining is and how it presents itself.

The Sympathetic Nervous System controls the fight-or-flight response. This response releases the hormones; cortisol, epinephrine (which is also known as adrenaline), and norepinephrine. Epinephrine’s job is to increase heart rate during periods of stress and high activity. Epi, as it is also called, also constricts blood vessels which elevates blood pressure and helps to get blood to muscles which demand it. Cortisol, like Epinephrine is also produced in the Adrenal Glands during fight-or-flight. Cortisol is responsible for increasing blood sugar in the body to provide readily available and fast burning fuel. During fight-or-flight Cortisol also suppresses the immune system and aids in fat metabolism.

The Parasympathetic Nervous System controls "rest and digest" hormones as opposed to fight-or-flight. Its job is to allow for digesting food and relaxing. It works mostly by inhibiting uptake of hormones involved in fight-or-flight response such as epinephrine and cortisol.

Sympathetic Overtraining refers to an overactive sympathetic nervous system producing TOO MANY stress hormones. This is typically brought on by too much anaerobic work or work near lactate threshold. Parasympathetic Overtraining refers to a sympathetic nervous system which has been so taxed, which may be fatigued, and the Parasympathetic Nervous System, actually begins to gain control over the weak and fatigued SNS. This is confusing language because both forms of overtraining actually involve over stimulation of the Sympathetic Nervous System, as it is responsible for raising heart rates even during aerobic exercise. The difference is where the balance of power falls. As stated, in Sympathetic Overtraining, the SNS is overactive, and in Parasympathetic Overtraining the SNS is underactive or "fatigued" and unable to produce the necessary hormones to raise heart rate. It is unfortunate the labels stuck, and the titles are as they are.

When most magazines and internet sources are discussing overtraining, they usually refer to the symptoms that are present in sympathetic overtraining;

• Fatigue

• Trouble Sleeping

• Weight loss

• Decreased performance

• Frequent illness and colds

• Overuse injuries become present

• Elevated morning heart rate

• Elevated cortisol levels



The only two symptoms which are not subjective are an athletes morning heart rate, and an athletes cortisol levels. Unfortunately, these two factors are usually NOT affected during overtraining by endurance athletes! Even subjective symptoms like an inability to sleep are opposite during Parasympathetic overtraining. During parasympathetic overtraining, one might be able to sleep like a baby for 12 hours per night. This is because there is no sympathetic stimulation to "stress" the athlete preventing restful sleep. Also in the same vein, athletes experiencing parasympathetic overtraining might notice an INCREASE in weight and body fat percentage or no change at all, as cortisol is not burning fat and harvesting glucose, the opposite is actually occurring in the body. The body digests everything and takes fuel in the bloodstream to digest it and store it.

Endurance athletes are likely to see overtraining presenting itself in an, INABILITY TO MAINTAIN A "NORMAL" HIGH HEART RATE RELATIVE TO PERCEIVED EFFORT. What this means is that if an athlete always averages about 140 beats per minute during a given workout, and over several weeks, the athlete finds that even with the same or even a higher effort, he is at a lower heart rate, like around 125, he may be overtrained.

{One method I found to monitor the state of my training, was to log my rate of perceived effort for given workouts, relative to my average heart rate. My RPE scale was 1/20, and HR was in beats per minute. There are multiple ways to track this. You could even give each day a ratio value, like say your RPE was 15 out of 20, and your HR was 155. Your load that day could be .75 (which is RPE 15/20) multiplied by 155, which equals 116.25. You can track this value daily, during overtraining your RPE might be 15/20 but your HR for the workout was only 139 giving your daily number a value of .75*139= 104.25 The purpose of this article is however bringing light to overtraining athletes, NOT discussing methods of prevention. That will be a later topic, as we must also focus on the third variable to assessing daily load, which would be volume!}

If you went on most internet forums, and inquired on why your heart was low for a given workout, the answers that are available are absurd. Most of the respondents are laymen at best, with ZERO understanding of physiology, and they actually reply that it is due to advanced fitness, larger cardiac output, etc! True, true, with greater fitness comes lower heart rates for given efforts, but this is so gradual and unnoticeable in the short term it isn't applicable to overtraining. If overtraining was occurring it is likely that a heart rate for a given workout would be possibly ten beats per minute lower or even more! Heart rates lowering due to advanced fitness occur in timeframes that are so long they become baselines which gradually shift, they would not lower 10 beats or more for a given workout in a period of only one month.

Unfortunately, what I have presented here is mere anecdotal evidence, but IT IS MY HYPOTHESIS. There are many other merely anecdotal research articles which tell stories of German cyclists and Ironman Triathletes experiencing the exact same phenomenon and after taking time off, resting and recuperating only doing exercise which was at VERY low intensity under 110 beats per minute, the athletes were once again strong, performing at normal HR expectations. This may take anywhere from days to weeks or more. I do know, from experience, that it has generally taken me two months at very low intensities to recover, and as a counter balance now, I make sure to track my heart rate constantly. I do not work out at or above lactate threshold more than 15% of my weekly miles or volume...This was also the foundation of Ironman Champion Mark Allen's training program.

The only time we become stronger as athletes is when we recover. Overtraining is in direct conflict with getting faster, and as much of a science the endurance sports are and have become, it is amazing I have to piece together various 1st hand research regarding adrenal fatigue and second hand and anecdotal stories and research regarding Heart-Tired Syndrome which is what Parasympathetic has been written about before. With much research I have determined the cause to be a weakened adrenal system, but the heart and body are complex. Conduction delays in the heart cannot be ruled out, with many athletes being diagnosed with cardiac arrhythmias who overtrain, and also with the endocrine system at play I haven't even mentioned how the heart cannot beat fast without an adequate supply of glycogen!

In regards however, to the common issue of endurance athletes being incapable of elevating their HR for a given workout to their "normal" HR, we must first look to Parasympathetic Overtraining. Unfortunately, there is no diagnosis medically for this as many cardiologists and doctors have absolutely ZERO idea what is at play here.

Signs and Symptoms of Parasympathetic Overtraining are as follows. (These S&S may or may not include all ;)

• Fatigue

• Depression

• Decreased Performance

• Achy legs at night

• INABILITY TO REACH NORMAL HEART DURING EXERCISE

• Possible craving of carbohydrates and caffeine

• Overuse injuries

• Normal heart rate while at rest or LOWER HR than usual

• Low Blood Pressure

The craving of carbohydrates is a response by the body to provide quick burning fuel which usually provides ample energy supply. Many Ironman and Ultra running athletes know that when they "bonk" or "hit the wall" that their HR plummets. This is not because of overtraining in a one day event, but because the body only functions at high levels while it has an adequate carbohydrate supply. The body can store approximately 2000 calories, (if the athlete is superbly trained at an elite level), and once the body has no more glycogen, (AKA "Carbs") to burn, the body must resort to burning fat as fuel which is much more inefficient.

Athletes who do not race with heart rate monitors could not witness this phenomenon. In the comments field below, please comment on stories from your races of over 3 hours in which you noticed your heart drop during an endurance race. As stated before, this article is anecdotal, yet I want all of the stories I can get to study the situation of HR and power, as well as HR and overtraining.

Hopefully this data can be objectified. In the next few days I will post links to all the articles which discuss Heart Tired syndrome I found online, as well as those which are relevant in regards to overtraining, Parasympathetic Overtraining, and Adrenal Fatigue/Insufficiency.

Please comment on this article and don't hesitate to ask questions and bring up other possible causative factors.

PS- Sorry if this piece doesn't flow well...I sort of whipped it out in a rush and haven't really proof read or edited yet...but hey, the important stuff is present!