It’s happened to the best of us: We gear up, cue up a killer cycling routine, and head straight for the gym— only to find out it’s temporarily closed (curse you, maintenance!). With heavy hearts and glutes dying to feel the burn, we sullenly make our way back home. At this point, you may be tempted to give up for the remainder of the day, but don’t change out of your gym clothes just yet! You already have the only workout machine you need on you.
1. It strengthens the heart. The heart is a muscle. Like other muscles, its performance improves when it's regularly challenged by exercise. The heart responds to exercise by becoming stronger and more efficient. Strengthening the heart muscle can help ward off heart disease -- the leading cause of death in the United States, according to the U.S. Department of Health and Human Services -- even in early childhood.
Exercise improves physical health. Physically active individuals have a much better health outlook than their sedentary peers. Even modest regular physical activity has a positive influence on people's health and vitality. A minimum of 20 to 30 minutes of moderate activity a day most days of the week will benefit health and assist with weight loss. A formal workout is not necessary to have these benefits; a brisk walk will suffice (although a more vigorous workout will suffice that much more).
It decreases PMS. Women often report feeling irritable and bloated before their periods, but exercise appears to minimize these conditions. In a survey of nearly 2,000 New Zealand women, researchers found that those who exercised, rested and wrote in a journal about their symptoms fared better than those who took specific vitamins or followed other DIY advice.

Most gymgoers who are struggling with flabby arms either spend hours on the treadmill or work their biceps day in, day out. What you should focus on are the triceps because this muscle makes up two-thirds of your arm. Train it once or twice per week to lose arm fat and build upper-body strength. Your arms might get bigger, but they'll look leaner and more defined.

This is a particularly cool one. Neuroscientists used to believe the brain was the only organ incapable of growing new cells—which partly makes sense, since we need our brains to be relatively stable over time, to keep our memories intact and to keep us us. But in recent years, it’s become clear that the brain, too, can grow new neurons, in a process called neurogenesis. And what seems to spur the growth of new neurons, perhaps above other activities, is aerobic exercise. (Other things, like meditation and antidepressant medication, have also been shown to trigger brain new cell growth.) The area of the brain that seems most capable of growing new cells is the hippocampus, the seat of learning and memory. It's also the area that’s known to “shrink” in depression, and particularly in dementia—so the fact that we may have some control over its health is exciting.


A combination of aerobic workouts (which, depending on your fitness level, can include walking, running, swimming, and other vigorous heart-pumping exercise) and strength training (weight lifting, resistance training) is considered best for heart health. These exercises improve the muscles’ ability to draw oxygen from the circulating blood. That reduces the need for the heart—a muscular organ itself—to work harder to pump more blood to the muscles, whatever your age.

Studies have consistently shown that physical activity can help treat depression, and on the flipside, that low activity levels are a big risk factor for it. The antidepressant effect of exercise seems to be moderated in part through serotonin, the brain chemical that’s targeted with some antidepressants, and in part through bone-derived neurotrophic factor (BDNF). And this goes back to the generation of new cells mentioned earlier—exercise, though various mechanisms, seems to make the brain more plastic and more capable of growing new cells.


Exercise has long been correlated with a longer life, but it’s only recently started to become clear why this might be. Studies, like a new one in the journal Preventive Medicine which found that exercise is linked to longer caps at the ends of chromosomes, have helped flesh this out a bit more. These caps, called telomeres, naturally shorten as we age, with each cell division. People who live a long time have telomeres that are in better shape than those who don’t—but there’s a lot we can do to affect the rate at which they shorten over the years. The team behind the new study looked at data from CDC's National Health and Nutrition Examination Survey, and found that for people who exercised regularly, their telomeres were 140 base pairs longer on average than sedentary people's. Which correlates to being years “younger” than their sedentary peers. 
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