Why exercise doesn't take, but instead optimizes your mental energy

Contrary to what you might have read, we haven't evolved to exercise. 

According to Harvard paleoanthropologist Daniel Lieberman, daily movement was non-negotiable for early humans. 

With all that necessary hunting and gathering required to survive, voluntary physical activity for the sake of health – that is, exercise – was not a thing for our "Old Stone Age" ancestors. 

As a result, we evolved to avoid physical activity whenever feasible. This notion resonates with many people living on a busy schedule: Exercise seems to be yet another demand that takes away scarce time from their professional and private lives.

However, that's an illusionary trade-off. Like light and nutrition, exercise is not only vital for our health, but also one of the most powerful levers to pull for optimizing our mental energy (aka autonomic arousal) around the clock in the modern world.

As John Ratey wrote in his book Spark, "if exercise came in pill form, it would be plastered across the front page, hailed as the blockbuster drug of the century." Let’s explore why.

A supercharged 401(k) for the brain

Chances are you've heard about the many long-term benefits of exercise for your body, such as preventing obesity, cardiovascular disease, type 2 diabetes and even several common cancers.

In her TED talk "The Brain-Changing Benefits of Exercise", Wendy Suzuki of New York University claims that "the most transformative thing that exercise will do is its protective effects on your brain".

"You can think about the brain like a muscle," Suzuki continues in her talk: "The more you're working out, the bigger and stronger your hippocampus and prefrontal cortex gets."

These two brain areas respectively underpin our working memory and impulse control – and also are the most susceptible to cognitive decline in aging and neurodegenerative diseases. Against this background, Suzuki compares exercise to a "supercharged 401(k) for the brain".

The golden rule of exercising

Now, if you have trouble getting motivated by long-term benefits, bear with me for a moment. In 2017, Suzuki published a review paper on the benefits of acute exercise – meaning only one session of exercise.

As it turns out, exercise is an excellent tool for optimizing our mental energy and, by extension, our productivity and well-being: When you're feeling somewhat tired, getting some exercise will bring you back up to moderately high levels of autonomic arousal – that is, towards the sweet spot of being both alert and calm.

Exercise does that by increasing the amount of the "alertness chemical" epinephrine and the "molecule of motivation" dopamine for up to two hours. As a bonus, exercise improves our executive functions – including working memory and impulse control – for the same amount of time.

Exercise also is an excellent way to bring your autonomic arousal down whenever you're more alert (read, stressed) than you'd like. As Suzuki describes in her review paper, exercising makes us calmer by decreasing activity in our sympathetic nervous system – for up to three hours. On top of that, it enhances positive mood states and decreases negative mood states for up to 24 (!) hours.

Taken together, no matter where you are on the arousal continuum throughout the day, exercise will move you toward the sweet spot of moderately high mental energy, where you are both alert and calm.

Just like light and nutrition, exercise thus allows you to optimize your mental energy throughout the day. And while it takes a bit of time, it’s worth the investment many times over – because it allows us to accomplish what matters at work in less time and with less stress.

Against this background, here's my golden rule for exercising: Exercise for its acute benefit of getting you back to that optimal state of alert and calm throughout the day. If you’re doing that, exercising habitually becomes much more manageable, and the long-term health benefits naturally follow.

Exercising on a busy schedule

According to the American Heart Association (AHA), healthy adults should get 150 minutes of moderate or 75 minutes of vigorous exercise per week – or, even better, a combination of both.

The AHA also recommends moderate to high-intensity muscle-strengthening activity, such as resistance or weight training, at least twice per week. While that might seem like a lot, getting to that dose is feasible, even on the busiest schedules.

The longer and more stressful your days, the more you will get out of making time for exercise. Here are some battle-tested practices that you might find helpful.

1. Include moderate exercise throughout the day
   The simplest and most universal moderate exercise is walking, and almost everyone can add more of it to their routine. Three simple tips effortlessly get you to 150 minutes of walking per week.
   
   First, walks are a great way to start or end your workday. If you're commuting, walk a part of the way – by getting on or off the tram or car at a nice walking distance from your office. If you're working from home, have a walk around the block to start or end your day.
   
   Second, commit to taking the stairs instead of the elevator. It's a great, cost-free way to get your steps in and reap the benefits for your productivity and health. Also, only sit when necessary, notably by doing walking meetings and calls instead of sitting ones whenever feasible.
   
   Third, take a walk shortly before or after meals. It will prevent huge spikes and crashes in your blood sugar levels, further stabilizing your mental energy.
   

2. Do vigorous exercise whenever you want to get back to being alert and calm
   Include vigorous exercise in your workday strategically: Do it whenever your mental energy is not where you want it to be.
   
   A helpful first step towards that goal is timing vigorous exercise based on your chronotype: If you're a morning lark or intermediate third bird whose energy wears out by the (late) afternoon, schedule your exercise for later in the day to recharge your mental energy.
   
   'If you're an evening owl, your sluggish (early) morning poses an ideal opportunity for vigorous exercise – even if that’s hard at first.
   
   Two to three weekly sessions of 25 to 40 minutes – ideally including some muscle-strengthening activity – get you into the target zone of 75 minutes.
   

3. Be cautious about vigorous exercise in the later evening
   As described above, moderate exercise in the evening – like a walk after work or dinner – is a great idea.
   
   Yet, vigorous exercise in the later evening is something you should treat with caution, because it makes you alert at a time when you'd rather be drowsy and finally deeply asleep.
   
   Why? Vigorous exercise increases both heart rate and body temperature, making it harder to fall asleep. Therefore, avoid vigorous exercise that increases your heart rate above 125 BPM in the last three hours before bed.

TL;DR

Here’s how to include exercise for optimal mental energy on a busy schedule:

1) Exercise to get its acute benefits for your mental energy – and bring yourself back to the optimal state of alert and calm throughout the day.

2) Do more moderate exercise by starting or ending your workday with a walk, always taking the stairs, doing walking meetings, and walking before or after meals.

3) Go for vigorous exercise to get back to being alert and calm during the day – and avoid increasing your heart rate to above 125 BPM in the last three hours before bed.

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Until next week,
Christian