Physical exercise is any bodily activity that enhances, develops, or maintains physical fitness and overall health. It is often practiced to strengthen muscles and the cardiovascular system, and to hone athletic skills.
Frequent and regular physical exercise boosts the immune system and helps prevent heart disease, cardiovascular disease, Type 2 diabetes, and obesity. Physical exercise has also been proven to improve mental health, reduce insomnia, and help prevent or offset the effects of depression.
As focus on the interconnectedness between the body and the mind increases, and as the population in the United States ages links between nutrition, exercise, and improved memory and cognition are becoming increasingly important. Mind/Body exercises are gaining popularity due to their many proven physical benefits as well as emotional benefits—particularly for managing stress and anxiety. Many forms of mind/body exercises are beneficial for people with conditions that might not allow them to participate in “regular” forms of exercise, but they can also help advanced exercisers enhance their fitness levels and become more balanced.
The benefits of exercise also need be balanced with an understanding of the detrimental effects of many modern substances now have on the human body. News reports informing conscientious consumers about controversies in regards to exercise—whether it be concerning the use of steroids, nutritional supplements or over training—have become common.
Exercise types and recommendations
Exercises are generally grouped into three types depending on the overall effect they have on the human body: They are: flexibility exercises such as stretching or yoga which improve the range of motion of muscles and joints; aerobic exercises such as cycling, walking, running, hiking, and playing tennis which focus on increasing cardiovascular endurance; and anaerobic exercises such as weight training or sprinting which increase muscle mass, strength, and power.
Recommendations for adults include incorporating both cardio or aerobic activities and resistance, strength-building, and weight-bearing activities into their weekly activities. Stretching, flexibility and "light activity" can be incorporated fairly easily on a daily basis.
It is recommended that children and adolescents participate in at least 60 minutes of moderate intensity physical activity most days of the week, preferably daily.
Physical exercise is important for maintaining physical fitness and can contribute positively to maintaining a healthy weight; building and maintaining healthy bone density, muscle strength, and joint mobility; promoting physiological well-being; reducing surgical risks; and strengthening the immune system.
Exercise can be beneficial to the brain by increasing the blood and oxygen flow to the brain, and by increasing growth factors that help create new nerve cells. Exercise also helps to release chemicals in the brain such as dopamine, glutamate, norepinephrine and serotonin that are known to add to a person's sense of well being.
Frequent and regular aerobic exercise has been shown to help prevent or treat serious and/or life-threatening chronic conditions such as high blood pressure, obesity, heart disease, and Type 2 diabetes. Strength training appears to increase one's basal metabolic rate so as to burn more calories in a 24 hour period than would aerobic training alone. Strength training, however, does not offer the same cardiovascular benefits of aerobic exercises.
There is conflicting evidence as to whether vigorous exercise (more than 70 percent of VO2 Max) is more or less beneficial than moderate exercise (40 to 70 percent of VO2 Max). Some studies have shown that vigorous exercise executed by healthy individuals can effectively increase opioid peptides, a naturally occurring opiate that in conjunction with other neurotransmitters is responsible for exercise induced euphoria. These endorphins are also said to positively influence hormone production (that is, both increased testosterone and growth hormone).
As focus on the interconnectedness between the body and the mind increases, and as the population in the United States ages studies that show a link between nutrition, exercise, and improved memory and cognition are becoming increasingly important to health professionals.
Exercise has been shown to improve cognitive functioning via improvement of hippocampus-dependent spatial learning, and enhancement of synaptic plasticity and neurogenesis. In addition, physical activity has been shown to be neuroprotective in many neurodegenerative and neuromuscular diseases, as in the case of its ability to reduce the risk of developing dementia. Physical activity is thought to have other beneficial effects related to cognition as it increases levels of nerve growth factors, which support the survival and growth of a number of neuronal cells.
Both aerobic and anaerobic exercise also work to increase the mechanical efficiency of the heart by increasing heart blood volume or myocardial thickness.
Active exhalation during physical exercise helps the body to increase its maximum lung capacity, and oxygen uptake. This results in greater cardiac efficiency, since the heart has to do less work to oxygenate the muscles, and there is also increased muscular efficiency through greater blood flow. Consciously breathing deeply during aerobic exercise helps this development of the heart lung efficiency.
Not everyone benefits equally from exercise. There is tremendous variation in individual response to training: where most people will see only a moderate increase in endurance from aerobic exercise, others will as much as double their oxygen uptake This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population.
"Targeted fat reduction"
Spot reduction is the mistaken belief that exercising a particular body part will shed the fat on that part; for example, that doing sit-ups would be the most direct way to reduce subcutaneous belly fat. In actuality, one cannot reduce fat from one area of the body to the exclusion of other areas. Most of the energy derived from fat gets to the muscle through the bloodstream. Reduction of stored fat occurs in the entire body, from the last place where fat was deposited. Sit-ups may improve the size and shape of abdominal muscles, but will not specifically target belly fat. Such exercise might help reduce overall body fat and shrink the size of fat cells. However, there can be a very slight increase in the fat reduced at the area being exercised (for example, the abs) compared with the rest of the body, due to extra blood flow to the area.
"Muscle turning to fat"
Some people incorrectly believe that muscle tissue will turn into fat tissue once a person stops exercising. This is not literally true—fat tissue and muscle tissue are fundamentally different—but the common expression that "muscle will turn to fat" is truthful in the sense that catabolism of muscle fibers for energy can result in excess glucose being stored as fat. Moreover, the composition of a body part can change toward less muscle and more fat, so that a cross-section of the upper-arm for example, will have a greater area corresponding to fat and a smaller area corresponding to muscle. This is not muscle "turning to fat" however, it is simply a combination of muscle atrophy and increased fat storage in different tissues of the same body part.
Another aspect to increased fatty deposits in a person who has stopped exercising is that of diet, given that most trainees will not significantly reduce their food consumption in order to compensate for the lack of exercise/activity.
Exercise is a stressor and the stresses of exercise have a catabolic effect on the body—contractile proteins within muscles are consumed for energy. Carbohydrates and fats are similarly consumed and connective tissues are stressed that can result in the formation of micro-tears. However, given adequate nutrition and sufficient rest (and thereby avoiding overtraining), the body's reaction to this stimulus is to adapt and replete tissues at a higher level than that existing before exercising. The results can then be the desired effects brought about through regular training and exercise—increased muscular strength, endurance, bone density and connective tissue toughness.
Too much exercise can be harmful. The body part being exercised needs at least a day of rest, which is why some health experts say a person should exercise every other day or three times a week. Without proper rest, the chance of stroke or other circulation problems increases, and muscle tissue may develop slowly.
For many activities, especially running, there are significant injuries that occur for those with unbalanced exercise regimens. In extreme instances, over-exercising induces serious performance loss. Unaccustomed over exertion of muscles leads to rhabdomyolysis (damage to the muscle); a condition often seen in new army recruits. Another danger is in overtraining to the degree that the intensity or volume of training exceeds the body's capacity to recover between bouts.
Stopping excessive exercise suddenly can also create a change in mood. Feelings of depression and agitation can occur or re-occur, as the case may be, when withdrawal from the natural endorphins produced by exercise sets in. While one person's set of joints and muscles may have the tolerance to withstand multiple marathons, for example, another person's body may be damaged by just twenty minutes of light jogging. An approach to exercise must, therefore, be individualized to fit each person's needs and body type.
Excessive exercise can also cause a female to stop menstruating, a condition known as amenorrhea (also called athletic amenorrhea). It was thought for many years that low body fat levels and exercise related chemicals (such as beta endorphins and catecholamines) disrupted the interplay of the sex hormones estrogen and progesterone. However recent studies have shown that there are no differences in the body composition, or hormonal levels in amenorrheic athletes. Instead, amenorrhea has been shown to be directly attributable to a low energy availability. Many women who exercise at a high level do not take in enough calories to expend on their exercise as well as to maintain their normal menstrual cycles.
Two other concerns in regards to excessive exercise are:
- Possibility of sudden death. Although death due to excessive exercise has occurred, isolated instances tend to be rare. Water intoxication can result from prolific sweating (producing electrolyte losses) combined with consumption of large amounts of plain water and insufficient replenishment of electrolytes, especially salt and potassium (An example of this happening would be during a marathon.) It is also possible to die from a heart attack or similar affliction if overly intense exercise is performed by someone who is not in a reasonable state of fitness preparedness for that particular activity. A doctor should always be consulted before any radical changes are made to a person's current exercise regimen. Other common dangers during exercise may occur from extreme overheating or aggravation of a physical defect, such as a thrombosis or an aneurysm.
- Weightlifting stunts growth. One caveat is that heavy weight training in adolescents can damage the epiphyseal plate of long bones.
Nutrition and recovery
Proper nutrition is at least as important to one's health as exercise. When engaging in an exercise regimen it becomes critical to maintain a healthy diet in order to ensure that the body is receiving the proper balance of macronutrients and micronutrients.
This balance, in particular, will aid the body with the recovery process that follows strenuous exercise. Proper rest and recovery are also as important to health as exercise, otherwise the body exists in a permanently injured state and will not improve or adapt adequately to the exercise. Hence, it is important to remember to allow adequate recovery between exercise sessions.
The role of exercise, nutrition and recovery in a person's life can be compromised by psychological compulsions such as eating disorders, exercise bulimia, anorexia, and/or obsessive compulsive disorder. In each of these cases a person's competitive drive to achieve a result through exercise becomes overly perfectionist or unbalanced. These conditions can all lead to an overall decreased state of health in the guise of staying "fit."
Delayed onset muscle soreness can occur after any kind of exercise, particularly if the body is in an unconditioned state relative to that exercise.
There are a variety of supplements used to enhance exercise or sports performance that fit into a broad category called ergogenic aides. An ergogenic aid can be broadly defined as a technique or substance used for the purpose of enhancing performance by improving energy production, energy control or energy efficiency. Ergogenic aids can be classified as nutritional, pharmacological, physiological, or even psychological. An ergogenic aid could include nutritional supplements such as creatine, protein powder, or carbohydrate loading. It's important that any one who uses these supplements to enhance performance activity, build muscle, or lose weight be aware of the various products on the market, their benefits and associated risks.
Despite efforts by WADA (World Anti-Doping Agency) and the Olympic Games Committee, numerous controversies have arisen over the abuse of steroids, EPO, and other performance enhancing drugs used by professional athletes to boost their competitive edge in sports from baseball, to wrestling, to the Tour de France bicycle race. Although some of these drugs have legal purposes their misuse is such that they pose a public health threat in terms of their scope and inability to be monitored even through mandatory drug testing.
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