Why you should exercise daily ?
What goes on inside your body when you pedal a bike or take a stroll? These activities set off complicated physical processes that affect nearly every organ system. When you exercise several times a week or more, your body adapts so you’re able to do so more efficiently. Knowing about this process will help you understand why physical activity has so many benefits.
Like all machinery, your muscles must have fuel. This fuel comes from the food you eat and your body’s reserves of fat and glucose. The catch is that nutrients from food cannot be turned directly into usable energy for the trillions of cells in your body. Each cell has one primary source of energy: a molecule called adenosine triphosphate (ATP). Your body’s ability to create ATP is critical because it determines your capacity for physical exertion. And the reverse is also true: your physical conditioning influences how well you can generate ATP.
The food you eat contains energy stored in a variety of forms — proteins, fats, and carbohydrates. Your body needs to extract that energy and capture it in the form of ATP. To do this, your stomach and small intestine break the food into millions of tiny molecules, which enter the bloodstream and find their way to every cell in the body (see the figure). There, in small cell structures called mitochondria, the food molecules undergo a series of chemical reactions that ultimately lead to the creation of ATP.
When you engage in physical activity, your body doesn’t rely solely on one process or the other; both are used to generate ATP, but one more so than the other. Because of this distinction, exercise is classified into two broad categories — aerobic and anaerobic — depending on which process is predominantly used for ATP production. If the intensity of exercise is such that your lungs and heart are able to supply oxygen for energy production, then the activity is almost exclusively aerobic. But if intensity rises so that demand for oxygen outstrips supply, then the activity becomes anaerobic. Walking, jogging, cycling, or swimming at an even pace are aerobic activities. Activities in which your body tends to go anaerobic more quickly include wind sprints and weight lifting.
Heart and blood vessels
Your cardiovascular system transports oxygen to cells and removes carbon dioxide, carries away metabolic waste products, and shuttles hormones to the intended organs. In addition, it helps maintain body temperature and preserve your body’s acid balance. Most people can engage in light activity, about the equivalent of walking 2 mph, without placing excess demand on their circulatory and respiratory systems. When you exercise more intensely, however, your muscles’ need for oxygen increases. Your heart must pump harder and faster. The amount of blood your heart pumps and the oxygen your body consumes rise in direct proportion to the amount of work your muscles are performing. And once again, your level of physical conditioning dictates how well this system works.
The greater need for oxygen-rich blood that occurs during aerobic exercise can also lead to an increase in the size and number of branches of the coronary arteries feeding the heart. This provides other channels for oxygenated blood to reach heart muscle. So if an artery serving the heart becomes blocked, heart muscle damage is less likely because alternative channels keep the blood supply flowing. The boost in oxygen and other benefits of exercise offer some protection against dangerous heart rhythm disturbances as well.
When you decide to move a part of your body, your brain transmits the message to your muscle fibers via your nerves. The fibers respond by contracting, which creates motion. To reverse the movement, your brain signals fibers in the opposing muscle group to tighten. For example, when you contract your biceps, the triceps on the back of your arm relaxes. Exercises that involve continuous motion, such as rowing, walking, or swimming, result in the rhythmic tightening and releasing of muscle fibers. In addition to moving your body, this process produces a “milking” action that helps move blood through your veins and back to your heart. With aerobic exercise, an increase in fibers containing iron-rich myoglobin also occurs, permitting more oxygen to enter and be stored in the muscle.
Throughout your life, your body is constantly building and dismantling bone tissue. This maintains your skeleton by replacing old bone with new bone and frees calcium, the main building block of bone, for other tasks. Calcium is vital to many physical processes, including maintaining heart rate and blood pressure, and a small amount of it circulates in your blood. When the amount of calcium in your blood gets low, your body draws on the reservoir of calcium stored in the bones. Early in your life, your body builds bone faster than it loses it. But with age, bone is lost more rapidly than it’s formed. Eventually, this leaves bones more fragile and susceptible to breaks. Exercise plays a key role in slowing bone loss. Muscle is tethered to bone by cords of tissue called tendons. Tendons tug on bones during physical activity. This stress increases bone strength and density. Exercises that work against gravity (such as walking, jogging, tennis, basketball, and strength training) provide the greatest benefit.
Exercise affects nearly all of the dozens of hormones your body produces. Two of these substances, epinephrine and norepinephrine, are key players in promoting physical changes while you are exercising. When your brain detects more muscle movement, it responds by releasing this pair of chemicals, which speed your heartbeat, contract arteries serving non-exercising parts of your body, and stimulate the release of sugars and fats from body stores for energy.
Endorphins, natural opiates that help block pain perception and may improve mood, rise after 30 minutes or more of exercise. Insulin, a hormone made in the pancreas, fluctuates in response to exercise. Insulin’s main function is to help usher glucose from the bloodstream into cells. While exercise boosts the concentrations of most hormones, levels of insulin drop during and for a short while after vigorous activity. This seems counterintuitive, because exercise accelerates the muscles’ demand for fuel in the form of glucose. However, insulin transports glucose more effectively during exercise, so less of it is needed.
Also, exercise seems to enhance your body’s ability to draw energy directly from fat stores. Research has found that exercise can also affect levels of estrogen. After menopause, when a woman’s ovaries stop producing estrogen, fat tissue becomes her body’s major source of estrogen. Some evidence suggests regular vigorous activity — and possibly moderate activity as well — may reduce circulating estrogen on an ongoing basis, partly because women who exercise tend to be leaner. This would expose breast cells to less of this hormone, which fuels many cancers.
Experts believe that moderate exercise reduces levels of stress hormones and other chemicals that suppress immune system functioning and increase inflammatory activity. Other changes occur, too. A 2005 study measured immune components in 15 healthy women during exercise and at rest. Researchers noted modest, short-term upswings in natural killer cells and white blood cells after 30 minutes of walking compared with sitting. Although the immune system returns to a pre-exercise state shortly after the exercise session is done, moderate activity on a daily or almost-daily basis seems to have a cumulative benefit for your immune system, improving its ability to fight off infection.