What do you think of when you hear the world adrenaline? Some of you might think of an adrenaline junkie, someone who needs to skydive out of planes to feel alive. Something that feels good to some or may even allow us to perform at our best. Others, might think of fear or feeling overwhelmed. The feeling of ‘too much’ adrenaline, that pushes us from excitement to nervous. Epinephrine and Norepinephrine make up what we commonly refer to as adrenaline. They cause shifts in arousal, vigiliance, motivation, attention, and a slew of other things that basically prepare us for the task at hand.

I’m sure many of you are familiar with the classic Yerkes-Dodson inverted U-model of optimal arousal. Too much arousal and performance declines, too little, and attention and focus aren’t there. It’s a great model to get across a simple point, but like most things in life, there’s more nuance behind it. When it comes to arousal, and adrenaline, timing matters.

In a now classic study, Hull and colleagues took a bunch of men and women, put them on a treadmill, ramped up the speed and incline and measured their adrenaline levels, among other items. At 9 minutes into the exercise test, they took a measurement, and then whenever the individuals called it quits from exhaustion.

Their baseline noradrenaline levels were 264, with little variation between subjects. But when separated into groups based on fitness and put through an exercise test, some interesting trends emerged.

Noradrenaline Levels9 minutesExhaustion
Group 1- Least Fit1,2372,555
Group 27213,730
Group 36155,506
Group 4- Most fit3546,250

So what does this all mean?

When it comes to adrenaline, it’s not just where you are before a performance that matters, or even how high or low you go. Timing matters. When working with athletes, I like to think of it as how much gas does your tank hold, and how quickly are using that gas? For top athletes, we want a large gas tank, while having great fuel economy. Because when we the going gets tough, we’ll need to burn through our supplies rather quickly.

And that’s what this data point to, that the fitter you are, the more efficient you are at using your adrenaline AND the higher capacity you have. When reaching complete exhaustion, our most fit individuals are producing about 3x that of our least fit.

The fitter a person was, the more efficient and the higher capacity their adrenaline system. In other words, under mild or even moderate stressors, the fit individuals only needed a small amount of adrenaline to take on the task at hand. This is important, because it allows you to ‘save’ more for later. By the time, the really difficult challenge comes, you’ve got a lot of fuel left in the tank. Not only that, but you’ve got a much larger fuel tank. So in those trying last few minutes of a race, your adrenaline is maxed out, 3x that of your lesser fit colleague at exhaustion.

We tend to think of adaptations from training in terms of the cardiovascular or muscular, but the entire body adapts to the stress placed under it. Aerobic training, like running, consistently shows an improvement in adrenaline efficiency and capacity. Just another perk to being fit.

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