You know that exercise is good for you, but many people don’t realize
just how important physical activity is for the brain. Exercise triggers
hormones and other changes in your brain that affect mood, thinking speed,
mental sharpness, and even athletic performance. Some of these effects
happen almost immediately during your workout and within hours afterward,
while other benefits are realized over the course of days and months as
you stick to your workout routine.
Here, I’ll break down exactly what is happening in your brain when
your body is hard at work on the Peloton Bike or Peloton Tread, and how
those benefits translate into better health and fitness overall.
During Your Workout
5 minutes: The brain gets an instant boost. As you ease into movement during
those first few minutes, you enter the “priming stage,” where
you experience a gradual increase in heart rate, breathing, and blood
flow to your muscles. At this time, oxygen and nutrients are also delivered
to your brain, which promotes the growth of new neurons.
20 to 30 minutes: Endorphins and endocannabinoids are released. Endorphins
are feel-good hormones produced by the brain. Endocannabinoids are similar
body chemicals that improve mood, stress response, memory, and more. These
hormones are released during moderate and intense exercise in response
to stress and other physiological changes that happen when you work out.
These chemical messengers help reinforce a positive association with exercise.
The same chemicals are also released whenever you do something pleasurable,
such as eating a favorite meal, hang out with your friends or laugh at
a good movie. In essence, they make your brain say, “Ahhh, I want to do this again.” And while the post-workout “high” is often attributed to endorphins,
it’s likely that the release of endocannabinoids plays a major role
in that “conquer the world” feeling you have after exercise.
After Your Workout
60 minutes: BDNF production increases. Exercise, especially HIIT, increases
the production of an important brain chemical called brain-derived neurotrophic
factor (BDNF). We still have a lot to learn about BDNF, but we know it’s
a molecule that helps our brains work properly, especially when it comes
to mood, learning, and memory. You can think of BDNF as a substance that’s
improving traffic, connections, and communication within the brain, all
while encouraging brain growth.
As we get older, BDNF production declines. However, according to several
studies, including one published in
Frontiers in Cellular Neuroscience, BDNF production spikes after a single HIIT workout. This increase is
temporary (you’ll have to exercise regularly to see more permanent
benefits), but it boosts focus and concentration in the short term.
2 to 4 hours: A second wave of brain chemicals are released. Here’s
where the real magic happens. In addition to endorphins and endocannabinoids,
other neurotransmitters, such as serotonin, dopamine, and norepinephrine,
begin to kick in 2 to 4 hours after your workout. These brain chemicals
are pretty amazing, and they deliver messages between neurons.
For instance, serotonin sends messages that affect a wide variety of
brain circuits relating to mood, sleep, appetite, and more. Not having enough serotonin is associated with depression and low mood,
while increased levels of serotonin have been shown in studies, including this
one, to have a positive influence on mood, cognition, and impulsivity (i.e.
increasing your ability to think through decisions before you make them)
in the short term. In the long term, a serotonin boost from exercise may
help reduce the risk of depression, according to research published in
JAMA Psychiatry that looked at the exercise habits of over 600,000 people.
Working out also increases norepinephrine, which improves your ability
to pay attention and focus on tasks. Dopamine, the reward substance, is
also released. Dopamine helps you feel a sense of satisfaction from exercise.
It’s also been shown in
research to play a role in working memory and mental flexibility. This is why many
of my colleagues and I routinely exercise in the morning on surgery days.
12 weeks: A sustained increase in BDNF. Doing regular aerobic or HIIT sessions
for a minimum of three months can spur additional production of BDNF,
according to several
studies. The short-term release we talked about earlier is associated with improvements
in concentration and focus, but when you get more BDNF over time, that’s
when you start to see the
impact on brain size, particularly in the areas of the brain associated with memory. Good news:
Rest days don’t interfere with this effect, so be sure to recover
between hard efforts. One
study found that exercising every other day over the course of three months
was just as effective at increasing BDNF levels as exercising every day.
3+ months: A healthy brain, a healthy body, and vice versa. Exercise increases
insulin-like growth factor 1(IGF-1), a hormone that plays a role in both overall physical health and brain
health. Having a healthy level of IGF-1 helps your body stabilize blood
sugar levels after you eat and improves insulin sensitivity.
Exercise increases insulin receptor density within three months of regular exercise, which also helps the body process
sugar more efficiently. Together, these things can have a positive impact
on cognitive health, since
poor metabolic health can increase your risk of cognitive decline. Most people don’t necessarily
think of the way their body processes sugar as related to brain health
but, at the end of the day, all of these things are linked to neurological function.
The Long-Term Benefits of Exercise
Fitness has a significant impact on cognitive function in middle age and
in the senior years and it can increase your overall “healthspan,”
or the number of years you live
in good health. Long-term exercise (over months and years) is associated with a larger
hippocampus, temporal lobe, and frontal lobe as you age—which are
the regions that are vulnerable to dementia—according to a 2021
review published in
Behavioural Brain Research. Evidence of smaller or atrophic hippocampal volume has been found in
individuals with dementia. Although there’s no direct “cause
and effect” link just yet, it is generally felt that a larger hippocampus
could be protective against dementia.
Being active may also help prevent age-related brain shrinkage, which starts
happening around age 40 and can lead to cognitive decline, notes a review
NeuroImage. Consistent exercise also reduces your risk of cardiovascular disease,
which is also associated with higher risks of developing cognitive impairment