First a little bit of background. In 1853 Claude Bernard discovered that the liver secretes your body’s main carbohydrate glucose by observing that the blood flowing out of the liver of fasted or meat fed animals contained glucose while the blood flowing into it contained little. When a cell takes in glucose from the blood it is modified by the process called oxidative phosphorylation (the major cell energy provider). This locks the glycogen molecule into the cell for future use. Only the liver can secrete glucose and it has the highest concentration of it. If you ever ate cooked liver, you know that it doesn’t taste sweet at all. That’s because the glucose in it stored as glycogen and glycogen does not taste sweet.
Liver contains 100 to 120 grams of glucose as glycogen. Compared to the liver, skeletal muscle contain less concentrated glycogen. However, because there is much more skeletal muscle than liver, we can they have much grated storage capacity. In total, your skeletal muscle contains 400 to 500 grams of glycogen. One gram of glucose produces 4 kilocalories of energy. Therefore the net energy stored in the liver is about 500 calories and about 1500 calories in skeletal muscle. Comparing trained and untrained individuals, more trained people are able to store more glycogen in their muscles and liver, however the difference is little. Average athlete might store 2000-2500 calories in total as usable carbohydrate energy in muscle and liver.
Carbs is preferred source of fuel for your body. They are easy to digest and provide fast energy. However due to the limited amount of them stored on board, you can easily deplete your carb storages just within 2 hours of moderate-intensity exercise.
75% of glycogen is used by the brain and central nervous system. For athletes, eating carbohydrates is like putting the octane in their engines. Consuming carbs will increase your blood glucose levels and help to fill your tanks before training or racing.
Glycogen is either created directly from food (glycogen synthesis) or through an indirect pathway (gluconeogenesis). When you eat a meal with carbohydrates, your body releases insulin, which takes glucose from the blood for energy into the cells. When the body gets excess fuel, the glucose molecules are linked together in a chain, producing longer units, called glycogen. As mentioned before, your body can store a limited amount of glycogen before it gets converted to fat.
FAT or CARBOHYDRATES for FUEL?
Adequate glycogen storage in your body is the key for optimal performance. Exercising at low and moderate intensities your body uses both: muscle glycogen and fat. The higher exercise intensity, the more carbohydrates are required to fuel your engine. Below is an example of how your body shifts from using fat for fuel towards running purely on carbohydrates. This is my VO2 test, conducted in professional laboratory:
Red column on a left is my heart rate (HR), measured in beasts per minute (bpm). Two columns on the right show the carbohydrate (CH) and fat (F) utilization related to heart rate. What we see here is that at lower intensities (<111 bpm) my body works primarily on fat as fuel. However the higher intensity of the exercise becomes, the faster my heart beats, more carbohydrates are being burned. Approximately at 111 bpm my body’s engine works as a pure hybrid, utilizing about the same amount of fat and carbohydrates for fuel. As the intensity increases, less and less fat is being used to fuel the exercise, until my body shifts completely to using carbs for fuel at 163 bpm.
Maintaining optimal carbohydrate stores is essential not only for good performance, but for protecting your health. Your nervous system, and brain primarily use carbohydrates for fuel. When glycogen stores get depleted and blood sugar level is low your brain will do anything to stop you from continuing exercising. You “hit the wall”. Pack your bags buddy, cause you are not going anywhere at this point. Consider yourself lucky if you finish the race.
What restores glycogen?
When the body experiences glycogen stores depletion, it takes about 24 hours to refuel (i.e., to ingest, digest, and convert food into glycogen). It is understood that carb-containing foods will help replenish stores the most efficiently. When food is digested, glucose is created. The pancreas recognizes this and produces insulin, a hormone that regulates the amount of glucose present in the bloodstream. Any glucose that isn’t used at this time is directed to the liver to be stored as glycogen.
There are two commonly used methods among athletes to store large amounts of glycogen is through carb loading and “training low”. We will get into these methods more in depth later in a book.
Unlike professional athletes, a lot of people manage to balance full-time jobs, family commitments and relationships with training. Training and competing, tight deadlines at work, travel across time zones, misunderstandings with people you care about, illnesses, dealing with difficult kids – all accumulate and add to psychological and physiological stress. Add on top of problems at work one or two hard training sessions, sprinkle it with sleep deprivation and you are well on your way to burnout and injury.
Mood swings, food cravings, inconsistency and unpredictability in athletic performance, lack of motivation, low energy levels are only the symptoms of system overload. You feel drained and totally destroyed. At 3 pm you fall asleep on the toilet at work, or worse, while driving back home. Total load is the term proposed by International Olympic Committee. In addition to your training and competing stress, it takes into account the daily life stressors.
Faster, better, stronger, harder! Sleep less, work more! Sleep for the weak! No pain – no gain! Chasing “gains” in our sports, we totally neglect psychological stressors and daily life hassles. We are so good at pushing ourselves, but so bad at recovering. Do you really think you can keep on abusing and pushing you body this way forever without any consequences? How long do you think you can last until it breaks? The question is not IF, the question is WHEN? Understanding the implications of total load and how to manage it – is critical to achieving your goals.
Modern technologies allow people to monitor so many body metrics: Heart rate during exercise; Resting heart rate (RHR); Sleep duration; Sleep stages; Caloric consumption and expenditure; Glucose and Ketone levels, you name it. We have access to data, that only a few decades ago was available to scientists in research labs. So many metrics at your hand and inability to make sense of it leads to information overload and analysis paralysis.
Information is gold. You will learn what the HRV is, and can it help you to improve your health, well-being and sports performance. I will teach you how to track and interpret your HRV data and show you real life examples of how daily life events and trainings impact your performance and recovery.
By default, Mother Nature has programmed your autonomic nervous system (ANS) with two operation systems: Sympathetic OS and Parasympathetic OS. They both work simultaneously, however performing totally different tasks.
Sympathetic Operation System
This is the system that has direct access to the “red button” which in situations threatening survival will prime your body for action.
Muscles contract, and begin to convert glycogen into glucose.
Heart rate ramps up.
Bronchial tubes dilate to facilitate better gas exchange.
Pupils dilate to enhance visual input, even in low light.
Hearing shuts down (auditory exclusion – loss of hearing).
You feel almost like rocket fuel has been poured into your system. Nitrous oxide is fueling your engine. You are READY TO EXPLODE at any second now. Flames are shooting down your exhaust pipes. Go get them!
This system saved your great-great-great-…-great father’s life, when saber-toothed tiger decided to have some homosapien for dinner. It is the reason why you are being alive. It was developed from necessity as a survival mechanism to prepare your body respond with everything it got in a matter of milliseconds. This system is awesome.
Parasympathetic Operation System
Unlike SO system, Parasympathetic OS is designed to slow you dow. This system is responsible to deploy the parachutes when the race is over. It maintains both mental and physical health by helping your body to calm down from stress reaction you’ve had and divert energy from other body processes to “rest and digest”. It’s a pit stop, where you get repaired, refueled and prepared for the next race.
Turns on digestion system, sending you to use the restroom
Makes you horny
Puts brakes on the heart rate and lowers the blood pressure after the sympathetic nervous system has activated the fight or flight response
Now that everything is behind, it’s time to chill and restore the energy you expanded.
HRV, What are you?
Heart Rate Variability – is the physiological phenomenon of variation in the time interval between heartbeats.
Unlike the car’s engine, your heart doesn’t beat with exact same frequency each moment. The pauses between beats are not equal and can range from 0.85 and 1.35 seconds.
Note: The longest intervals between beats occur when you exhale, and the shortest intervals when you inhale.
HRV is simply a measure of the variation in time between each heartbeat which is controlled by autonomic nervous system (ANS).
Is it Worth the Hype?
For the past 4 months, every single morning I measured my HRV using HRV4Training IOS app. It costed me $10 for the app which promised to provide data analytics on the relation between physiological parameters, training and performance. It does not require any extra sensors and use iPhones flashlight with camera to measure your heart rate (technique is called photoplethysmography). The process of measuring is really easy:
Place your fingertip exactly on the camera. Touch the camera gently
Try not to move for the duration of the whole test, and breathe freely, without forcing any unnatural breathing pattern
Stay still for 1 minute
After each measurement the app will output the HRV Score. Higher score (or greater variability between heart beats) usually means that the body has a strong ability to tolerate stress or is strongly recovering from prior accumulated stress. At rest, a high HRV is generally favorable and a low HRV is unfavorable.
I also been journaling my emotional conditions, energy levels and training performances during that time period. I collected a lot of data to see if there are any patterns or corrections between HRV and my athletic performances , as well as overall feeling.
Traveling & Racing
Ukraine, Euro-tour, Marathon, Half-Marathon
From December 29th to January 19th I put A LOT of stress on my body and mind. I flew to Kiev, Ukraine from Toronto changing 8 time zones. I visited 5 countries during the road trip through the Europe. I drove over 5,000 km. I ran a marathon on January 5th in Paris and a half-marathon week later. Below is the data I got from the app during that crazy trip:
Left picture shows the recovery points and the right one shows the heart rate. To my surprise, app measurements show that cross-continental flight to another part of the world didn’t harm my body too much, neither the marathon did. Almost throughout the entire time of travel, training and competing my recovery points stayed nice and high, even higher then when I was back home. Same story with heart rate. It stayed low during the entire time, showing the positive trend even after the marathon.
Looking at this graphs it seems that my body handled travel, training and racing very well. In fact the scores are better than I had, while back home in Canada.
This is where it gets really interesting! Immediately right after returning back home, everything went down. My recovery pointsfell straight down, continuing this negative trend for 7 days! We can also see direct correlation to heart rate readings. For a week it continued to creep up indicating that my body is having a really hard time.
My theory is that during the time spent traveling and in Ukraine, my body was under some sort of adrenaline or in defense mode to absorb the stress. Shortly after I returned back home and touched my bed, my body switched off the defense mode and literally fell apart.
Not to mention that despite downward trends Ifelt good mentally and emotionally.
Can HRV predict good and bad performances?
Let’s put travel and stress associated to the side and evaluate the data during regular training under normal conditions. Consistent journaling allows me to go back and see when I felt particularly good or bad, strength or weakness. I used my post-workout comments to compare them with HVR scores on that particular day.
Below Average / Bad Performances
In contrast to low HRV scores, let’s review some more recent data with higher scores. Did I feel and perform better with high HRV scores?
Great performances / Breakthroughs
“Information is only useful if it’s actionable“
Now that we reviewed the data, lets bring the elephant into the room and answer the main question:
Does HRV4Training provide data analytics on the relation between physiological parameters, training and performance?
In my case it DOES NOT.
During the 4 months of recording and comparing HRV data to my overall feeling I did not find direct relationship between HRV scores and athletic performances. It addition HRV score does not reflect mental or emotional state, neither it was promised by developers it would.
I am sure there are people who found this tool useful and will disagree with me. However everyone is different and what works for one, does not work for another. $10 for this particular app will not break your budget and I encourage you to give it a shot and see if you benefit from it. I am opened for discussion on the topic and I might change my mind, but for now I will stop measuring my morning HRV using the app for the reasons I stated above. Instead I will work to recognize the signs my body tell me, when something’s not quite right. I will also listen more to my emotional state to access my condition and predict the readiness to perform on a given day.
Soligard, T., Martin Schwellnus, J. A., Bahr, R., Clarsen, B., Dijkstra, P., Gabbett, T., . . . Engebretsen, L. (2016, September 01). How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. Retrieved March 7, 2019, from https://bjsm.bmj.com/content/50/17/1030
Schwellnus M, Soligard T, Alonso J, et al(2016, September 01). How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. Br J Sports Med2016;50:1043-1052. Retrieved March 7, 2019, from https://bjsm.bmj.com/content/50/17/1043
What is Heart Rate Variability (HRV)? And how it can enhance your training. (n.d.). Retrieved March 7, 2019, from https://www.myithlete.com/what-is-hrv/