What Happens to Your Body When You Exercise?

One of the key health benefits of exercise is that it helps normalize your glucose, insulin, and leptin levels by optimizing insulin/leptin receptor sensitivity. This is perhaps the most important factor for optimizing your overall health and preventing chronic disease.
But exercise affects your body in countless other ways as well—both directly and indirectly. Here,
however, even the most unexpected side effects are almost universally beneficial. For example, as illustrated in the featured article,¹ side effects of exercise include but are not limited to:

• Improved sexual function
• Changes in gene expression
• Clearer skin
• Improved mood
• Improved sleep

What Happens in Your Body When You Exercise?

The featured article in Huffington Post² highlights a number of biological effects that occur, from head to toe, when you exercise. This includes changes in your:

• Muscles, which use glucose and ATP for contraction and movement. To create more ATP, your body needs extra oxygen, so breathing increases and your heart starts pumping more blood to your muscles.
Without sufficient oxygen, lactic acid will form instead. Tiny tears in your muscles make them grow bigger and stronger as they heal.

• Lungs. As your muscles call for more oxygen (as much as 15 times more oxygen than when you're at rest), your breathing rate increases. Once the muscles surrounding your lungs cannot move any faster, you've reached what's called your VO2 max—your maximum capacity of oxygen use. The higher your VO2 max, the fitter you are.
• Heart. As mentioned, your heart rate increases with physical activity to supply more oxygenated blood to your muscles. The fitter you are, the more efficiently your heart can do this, allowing you to work out longer and harder. As a side effect, this increased efficiency will also reduce your resting heart rate. Your blood pressure will also decrease as a result of new blood vessels forming.
• Brain. The increased blood flow also benefits your brain, allowing it to almost immediately function better. As a result, you tend to feel more focused after a workout. Furthermore, exercising regularly will promote the growth of new brain cells. In your hippocampus, these new brain cells help boost memory and learning. As stated in the featured article:

"When you work out regularly, your brain gets used to this frequent surge of blood and adapts by turning certain genes on or off. Many of these changes boost brain cell function and protect from diseases such as Alzheimer's, Parkinson's or even stroke, and ward off age-related decline."


A number of neurotransmitters are also triggered, such as endorphins, serotonin, dopamine, glutamate, and GABA. Some of these are well-known for their role in mood control. Exercise, in fact, is one of the most effective prevention and treatment strategies for depression.

• Joints and bones, as exercise can place as much as five or six times more than your body weight on them. Peak bone mass is achieved in adulthood and then begins a slow decline, but exercise can help you to maintain healthy bone mass as you get older.
Weight-bearing exercise is actually one of the most effective remedies against osteoporosis, as your bones are very porous and soft, and as you get older your bones can easily become less dense and hence, more brittle -- especially if you are inactive.

Your Brain Health Is Directly Related to Exercise

A related article published by Lifehacker.com³ focuses exclusively on brain-related changes that occur when you exercise. While I just mentioned that neurotransmitters, chemical messengers in your brain, such as mood-boosting serotonin, are released during a bout of exercise, that doesn't account for all the benefits your brain reaps.

"If you start exercising, your brain recognizes this as a moment of stress. As your heart pressure increases, the brain thinks you are either fighting the enemy or fleeing from it. To protect yourself and your brain from stress, you release a protein called BDNF (Brain-Derived Neurotrophic Factor). This BDNF has a protective and also reparative element to your memory neurons and acts as a reset switch. That's why we often feel so at ease and like things are clear after exercising," Leo Widrich writes.

Simultaneously, your brain releases endorphins, another stress-related chemical. According to researcher MK McGovern, the endorphins minimize the physical pain and discomfort associated with exercise. They're also responsible for the feeling of euphoria that many people report when exercising regularly.
Scientists have been linking the benefits of physical exercise to brain health for many years, but recent research^{4, 5} has made it clear that the two aren't just simply related; rather, it is THE relationship. The evidence shows that physical exercise helps you build a brain that not only resists shrinkage, but increases cognitive abilities. Exercise encourages your brain to work at optimum capacity by causing your nerve cells to multiply, strengthening their interconnections, and protecting them from damage. There are multiple mechanisms at play here, but some are becoming more well-understood than others.
The rejuvenating role of BDNF is one of them. BDNF activates brain stem cells to convert into new neurons. It also triggers numerous other chemicals that promote neural health. Further, exercise provides protective effects to your brain through:

• The production of nerve-protecting compounds
• Improved development and survival of neurons
• Decreased risk of heart and blood vessel diseases
• Altering the way damaging proteins reside inside your brain, which appears to slow the development of Alzheimer's disease

Both Fasting and Exercise Trigger Brain Rejuvenation

Growing evidence indicates that both fasting and exercise trigger genes and growth factors that recycle and rejuvenate your brain and muscle tissues. These growth factors include BDNF, as just mentioned, and muscle regulatory factors, or MRFs.
These growth factors signal brain stem cells and muscle satellite cells to convert into new neurons and new muscle cells respectively. Interestingly enough, BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. (The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor degradation is part of the process that explains age-related muscle atrophy.)
So BDNF is actively involved in both your muscles and your brain, and this cross-connection, if you will, appears to be a major part of the explanation for why a physical workout can have such a beneficial impact on your brain tissue. It, quite literally, helps prevent, and even reverse, brain decay as much as it prevents and reverses age-related muscle decay.
This also helps explain why exercise while fasting can help keep your brain, neuro-motors, and muscle fibers biologically young. For more information on how to incorporate intermittent fasting into your exercise routine for maximum benefits, please see this previous article. Sugar suppresses BDNF, which also helps explain why a low-sugar diet in combination with regular exercise is so effective for protecting memory and staving off depression.

This Is Your Brain on Exercise

BDNF and endorphins are two of the factors triggered by exercise that help boost your mood, make you feel good, and sharpen your cognition. As mentioned by Lifehacker, they're similar to morphine and heroin in their action and addictiveness—but without any of the harmful side effects. Quite the contrary! So, how much do you have to exercise in order to maintain a sunnier disposition and better memory long-term?
According to a 2012 study⁶ published in the journal Neuroscience, the "secret" to increased productivity and happiness on any given day is a long-term investment in regular exercise. And a little each day appears to go further than a lot once or twice a week.

"Those who had exercised during the preceding month but not on the day of testing generally did better on the memory test than those who had been sedentary, but did not perform nearly as well as those who had worked out that morning," the authors note.

The reasons for this can perhaps be best perceived visually. Take a look at these images, showing the dramatic increase in brain activity after a 20 minute walk, compared to sitting quietly for the same amount of time.

There is a minor caveat, however. The researchers also discovered that exercise does not affect the brains of all people in exactly the same way. Some people, about 30 percent of people of European Caucasian descent, have a BDNF gene variant that hinders post-exercise BDNF production. The people with this BDNF variant did not improve their memory scores, even when exercising regularly, as significantly as those without this variant. Still, the research clearly suggests that—with individual variations as to the degree—regular exercise will cumulatively enhance your memory and other brain functions.

You Don't Need to Train Like an Athlete to Reap the Benefits of Exercise

Aim for a Well-Rounded Fitness Program

Ideally, to truly optimize your health, you'll want to strive for a varied and well-rounded fitness program that incorporates a wide variety of exercises. As a general rule, as soon as an exercise becomes easy to complete, you need to increase the intensity and/or try another exercise to keep challenging your body.
Additionally, more recent research has really opened my eyes to the importance of non-exercise movement. Truly, the key to health is to remain as active as you can, all day long, but that doesn't mean you train like an athlete for hours a day. It simply means, whenever you have a chance to move and stretch your body in the course of going about your day—do it!
And the more frequently, the better. Everything from standing up, to reaching for an item on a tall shelf, to weeding in your garden and walking from one room to another, and even doing dishes count. In short, it's physical movement, period, that promotes health benefits by the interaction your body gets with gravity.

• Interval (Anaerobic) Training: This is when you alternate short bursts of high-intensity exercise with gentle recovery periods.
• Strength Training: Rounding out your exercise program with a 1-set strength training routine will ensure that you're really optimizing the possible health benefits of a regular exercise program. You can also "up" the intensity by slowing it down.
• Stand Up Every 10 Minutes. This is not intuitively obvious, but emerging evidence clearly shows that even highly fit people who exceed the expert exercise recommendations are headed for premature death if they sit for long periods of time. You can decide to set a timer for 10 minutes while sitting, and then stand up and do one legged squats, jump squats or lunges when the timer goes off. The key is that you need to be moving all day long, even in non-exercise activities.
• Core Exercises: Your body has 29 core muscles located mostly in your back, abdomen and pelvis. This group of muscles provides the foundation for movement throughout your entire body, and strengthening them can help protect and support your back, make your spine and body less prone to injury and help you gain greater balance and stability.
Exercise programs like Pilates and yoga are also great for strengthening your core muscles, as are specific exercises you can learn from a personal trainer.

• Stretching: You hold each stretch for only two seconds, which works with your body's natural physiological makeup to improve circulation and increase the elasticity of muscle joints. This technique also allows your body to repair itself and prepare for daily activity.