What Happens to Your Body When You Exercise?

Having a consistent exercise routine is vital to your health in just about every way, so it's important to keep your hiatus as short as possible, to minimize your losses. You don't want your exercise habit to be replaced by the "habit" of not exercising.

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 in preventing chronic disease. A little exercise each day appears to go farther than a lot of activity once or twice a week.

It's also important to try to keep yourself in motion as much as possible during each day, as sitting too much is an independent risk factor for chronic disease and reduced life expectancy, even if you're very fit and exercise regularly. Walking 7,000-10,000 steps a day can be very helpful.

In addition to its positive metabolic effects, exercise has many other benefits for your mind and body. The increased blood benefits your brain and cardiovascular system, boosting oxygenation, cognitive function, and neurotransmitter production, which helps lift your mood.

Exercise also has proven benefits for sleep and sexual function and has been shown to "turn off" your fat genes. Exercise is indeed good medicine, but consistency is required... the minute you begin slacking off, those health benefits will begin fading away.

Getting Out of Shape Happens Faster Than You Might Think

How fast does your body decondition when you stop exercising? In three words—much too quickly! Anyone who has ever returned to the gym after a moderate absence will likely agree with me on that one. A number of studies have examined the "deconditioning" process, and there seem to be differences between new and seasoned exercisers.

In a recent article,1 sports medicine expert Elizabeth Quinn mentions a study that looked at well-conditioned athletes who'd been training regularly for a year before they stopped exercising. After three months, the athletes lost about half of their aerobic conditioning.

According to exercise scientist Wayne Westcott, a triathlete on a one or two month break may lose only five to 10 percent.2 But science suggests it's a different story for new exercisers.

Researchers 3 followed beginners who had exercised for two months and whose strength had increased by 46 percent. These beginners then stopped training for two months, which resulted in a strength loss of 23 percent—they lost half of their previous gains.

Another study 4 involved sedentary individuals as they started a bicycle fitness program for two months, during which time they experienced dramatic cardiovascular improvements. After eight weeks, these new exercisers quit exercising for two months. At the end of this period, they'd lost ALL of their aerobic gains and returned to their original fitness levels. If you're extremely fit and have been fit for a long of time, you may have accumulated some extra protection—but don't make the mistake of believing that your lingering fitness has no expiration date!

Training Hard in Your Youth Does Not Confer Lifelong Benefits

Most studies confirm that you should get out and exercise, regardless of your age or how fit you were in your younger years.

Studies generally support the old adage, "use it or lose it." A study 5 published in the British Journal of Sports Medicine concluded that physical inactivity is indeed a risk factor for metabolic syndrome in retired elite male athletes. Other research shows that longtime endurance runners lose muscle mass at the same rate as everyone else, including those who are sedentary—five pounds per decade, according to Dr. Westcott. 

This is not surprising when you consider that endurance cardio does not build or maintain muscle mass. For that, you need to do strength training. Strength training is extremely beneficial, regardless of your age. A 2011 study 6 found that if you do regular strength training in your youth and continue into your later years, your muscle strength will be easier to maintain as you age. The study also suggests that visiting the gym just once a week may be enough for younger and older adults to hold onto past strength gains—so the earlier you start getting in shape, the better.

A study 7 involving world-class kayakers highlights the importance of sticking with a regular fitness schedule. Kayakers who completely quit training at the end of their competitive season showed rapid loss of strength and endurance—losing nine percent of their muscular strength and 11 percent of their aerobic capacity after only five weeks. Oftentimes, you don't have to quit exercising altogether.

Cutting Back on Exercise Is Less Detrimental Than Quitting

Relatively small amounts of physical activity appear to be effective in maintaining at least some of your fitness progress. The kayakers in the above study who merely cut back to one weight training session and two endurance workouts per week lost less than half as much as those who quit exercising altogether. 8 In another study, 9 previously sedentary men did three months of strength training, three times a week, and then cut back to one session per week. These men maintained nearly all of their strength gains.

If you need to cut back, incorporating some form of high-intensity exercise on a weekly basis seems to improve your chances of maintaining your conditioning, even if you can't resume your full fitness routine for several months.

In order to do this successfully, you need to exercise at about 70 percent of your VO2 max at least once per week, according to Quinn. VO2 max (also known as maximal oxygen intake) is defined as the maximum volume of oxygen you can utilize in one minute of maximal or exhaustive exercise. 10

Your Brain May Get Flabby, Too

Flat abs and improved metabolic markers are not the only benefits you risk losing by taking an exercise hiatus. Two studies 11presented at the 2012 annual meeting of the Society for Neuroscience revealed that exercise's brain benefits may fade relatively quickly if you stop exercising. In the first study, active rats that had just one week of inactivity were pitted against completely inactive rats while performing memory tests. The previously active rats completed the tests much faster and had at least twice as many new neurons in the hippocampus region of their brains (memory center). It's important to reiterate, this change occurred after just one week of inactivity.

After three weeks of inactivity, their new neurons began to decrease, as did their performance on memory tests. After six weeks of inactivity, the neurons and memory test scores declined even further, leading the researchers to conclude, "exercise-induced benefits may be transient." In a second study, rats that were active for 10 weeks, followed by three weeks of inactivity, had brains that were nearly identical to those of rats that had been completely inactive. This is likely related to a reduction in brain derived neurotropic factor (BDNF) that exercise stimulates.

In prior studies, it was shown that exercise had a favorable effect on the animals' moods, making them less anxious and more resilient to stress, but the newer research suggests these benefits "wear off quickly." There is no way to predict exactly how fast you will lose your fitness gains if you stop exercising, as there are simply too many variables. However, the longer you go without exercising, the greater your losses will be—you can count on that.

Excess Sitting Is Dangerous, No Matter How Many Hours You Spend at the Gym

Intermittent daily physical activity is probably even MORE important than going to the gym. The dangers of excess sitting are well documented—sitting for extended periods of time is an independent risk factor for poor health and premature death, even for athletes.

No amount of exercise has been found to counter these effects. Research shows that excessive sitting is bad for your mental health as well, increasing your risk for depression, anxiety, and poor self-esteem.

The key is to stand up often—at least once every hour. I recommend doing a few exercises while standing up. Ideally, you'll want to avoid sitting altogether, as much as possible. Limiting your sitting to three hours or less per day can go a long way toward warding off a number of risk factors. Also consider getting a fitness tracker, and make a point of walking 7,000-10,000 steps per day. This is not in lieu of exercise, but in addition to it...

Natural health expert Dr. Joseph Mercola

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Sources and References:

1 Sports Medicine May 30, 2014

2 Women’s Health Magazine August 7, 2014

3 Women’s Health Magazine August 7, 2014

4 Sports Medicine May 30, 2014

5 Br J Sports Med 2010

6 Med Sci Sports Exerc July 2011

7 Med Sci Sports Exerc June 2010

8 New York Times December 29, 2010

9 Sports Medicine May 30, 2014

10 Sports Medicine May 16, 2014

11 New York Times January 9, 2013

12 Huffington Post August 11, 2014

13 Memory February 26, 2014

14 J Am Coll Health September-October 2005

15 Int J Eat Disord July 2007

16 Body Image March 2014