Can your immune system give you wings? The choose your own adventure blog.
So, in typical “Murphy’s Law” fashion, not long after I’d written about my training motivation, I managed to get the flu. My motivation was high, but my body was not up to it. Ironically, I’ve had to stop myself from exercising even though I really want to. So, I got to thinking about how our immune system works and more specifically the “fly then die” phenomenon that athletes sometimes experience. The day before you crash and burn with a cold you can sometimes feel amazing. It's like your body is turbo charged and the hard efforts feel easy, like you’re flying. Hence “Fly then die”.
My son Ethan experienced this for the first time at a recent local cycling club race we both attended. He woke early that morning feeling a little off, but still good enough to race. By the time we’d ridden to the race he felt fine. In the race he did personal record power for 1, 3 and 5 minutes, attacked the field multiple times, worked hard in a break away that was caught with half a lap to go and still managed to find more energy in the final sprint to score a podium that morning. By that afternoon he was feeling unwell and went to bed. He stayed there for four days.
Later that week we had our regular call with Ethan’s coach. He confirmed the fly then die phenomenon is a thing. All athletes experience it from time to time. The trick is to recognise when it’s happening and take it easy rather than keep pushing harder and harder because you feel awesome. It pretty much never happens when you want it to. The last day of a multistage race would be a great time. Rarely is anyone that lucky though.
A few days after that conversation with Ethan’s coach the same topic came up in a sports performance and coaching podcast I was listening to. Again, more anecdotal stories but no scientific explanation of what’s going on in our bodies that would help us achieve peak performances on the first or second day of a viral infection.
Obviously, this would be near impossible to research as you can’t know when you’re going to be sick, and you’ll never get ethics approval to infect athletes with influenza to study their immune response. This kind of research happens with rats and mice. Luckily there is mountains of research on our immune response and specifically to viruses like influenza so we can look at these to try to find a possible biological mechanism.
CAUTION!! Despite my best efforts to write a simple summary of the human immune system, Dr Christine, Quinn and Bronnie think the next few paragraphs are too full of scientific words and a bit hard to understand. Feel free to skip a few paragraphs and go straight to the to the super summary.
So how does our immune system protect us from a virus like influenza?
Our immune response is multi-faceted and highly complex and very well summarised all over the internet. In brief, our innate immune response is the first line of defence as an influenza virus enters our airways and begins to infiltrate the mucosal lining. Here the virus wants to enter our respiratory cells and use our own cellular apparatus to replicate its viral genome inside the cell, release more and more copies of itself and simultaneously kill the infected cell. Our immune system recognises a virus, and the humoral immune response is initiated. This inflammatory process helps quickly circulate immune cells that kill the virus and the cells that have already been infected.
How could this immune system response boost your performance?
This early response requires energy, so our immune system also upregulates a process called glycolysis to make adenosine triphosphate (ATP) or energy. Glycolysis takes place in the mitochondria inside our cells. Mitochondria are like the engine of the cell. Glycolysis is the process of turning glucose into ATP which is the energy our cells need. This early upregulation of energy production is one possible explanation for the fly then die phenomenon. You’ve just been infected with a virus, the virus hasn’t had time to replicate itself many times and the viral load is still very low, your humeral immune response has kicked in and energy production has ramped way up. You don’t feel unwell yet and can’t explain why you have boundless energy. You smash your race or work out, push your body to the limit and then fall in a heap soon after.
The good news is that your immune system also has another specific response to viral infection called the adaptive response. The adaptive response uses a different energy system called beta oxidation. Viruses mutate and change over time, so our adaptive immune system must recognise and remember new variations of viruses and stop them from replicating.
Until recently it was assumed that all cells infected with influenza were destined to die from either the virus itself or our protective immune response.
However, a recent 2019 article by Fiege et al. has shown that influenza A infected cells can survive infection and go on to replicate into healthy new cells. No doubt there will be more research and new discoveries that will continue to help us better understand how the immune system works. It’s also a timely reminder that everything we think we know about the human body is only true until we discover something different that helps us understand our biology in a new way.
Super summary here…
Before you feel the symptoms of the flu, your immune system is already hard at work. Hard work requires energy. Your immune system ramps up energy production. Therefore, there is a small window of time when you don’t feel sick and have more energy. Hence “Fly then Die”.
Fortunately, I’m already feeling well again. I’m glad my immune system is doing its thing despite the fact I/we don’t completely know how it’s doing it. My motivation to exercise is still high and forcing myself to rest has only made me want to ride my bike even more.
And I’m also pleased a few hours of research helped me answer a question that, if left unanswered would have bothered me for a long time. The fly part of the “fly then die” phenomenon is our immune system upregulating the same energy system we use during aerobic exercise.
Alistair.
The human antibody response to influenza A virus infection and vaccination (nature.com)
Immune response to influenza -- ScienceDaily
Long-term surviving influenza infected cells evade CD8+ T cell mediated clearance (plos.org)
https://pubmed.ncbi.nlm.nih.gov/25211638/
https://pubmed.ncbi.nlm.nih.gov/29556226/
https://pubmed.ncbi.nlm.nih.gov/32473386/
https://onlinelibrary.wiley.com/doi/full/10.1002/eji.201646342