FITNES

Fitness

Fitness (often denoted $w$ in population genetics models) is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype. In either case, it describes the ability to both survive and reproduce, and is equal to the average contribution to the gene pool of the next generation that is made by an average individual of the specified genotype or phenotype. If differences between alleles at a given gene affect fitness, then the frequencies of the alleles will change over generations; the alleles with higher fitness become more common. This process is called natural selection.

An individual's fitness is manifested through its phenotype. As phenotype is affected by both genes and environment, the fitnesses of different individuals with the same genotype are not necessarily equal, but depend on the environment in which the individuals live. However, since the fitness of the genotype is an averaged quantity, it will reflect the reproductive outcomes of all individuals with that genotype.

Inclusive fitness differs from individual fitness by including the ability of an allele in one individual to promote the survival and/or reproduction of other individuals that share that allele, in preference to individuals with a different allele. One mechanism of inclusive fitness is kin selection.

Levels of Services and Offerings

Health clubs offer a wide array of services, and as a result the monthly membership prices can vary greatly. A recent study of American clubs found that the monthly cost of membership ranged from US$15 per month at basic chain clubs that offer limited amenities to over US$200 per month at spa-oriented clubs that cater to families and to those seeking social activities in addition to a workout In addition, some clubs - such as many local YMCAs - offer per-use punchcards or one-time fees for those seeking to use the club on an as-needed basis.

Costs can vary through the purchase of a higher-level membership, such as a Founders or a Life membership. Such memberships often have a high up-front cost but a lower monthly rate, making them potentially beneficial to those who use the club frequently and hold their memberships for years.

Group Exercise Classes

Most newer health clubs offer group exercise classes that are conducted by qualified fitness instructors. Many types of group exercise classes exist, but generally these include classes based on aerobics, cycling (spin cycle), boxing, high intensity training, regular and hot (Bikram) yoga, pilates and muscle training. Health clubs with swimming pools often offer aqua aerobics classes.

Sports Facilities

Some health clubs offer sports facilities such as a swimming pools, squash courts or boxing areas. In some cases, additional fees are charged for the use of these facilities.

Personal Training

Most health clubs employ personal trainers who are accessible to members for training/fitness/nutrition/health advice and consultation. Personal trainers can devise a customized fitness routine, sometimes including a nutrition plan, to help clients achieve their goals. They can also monitor and train with members. More often than not, access to personal trainers involves an additional hourly fee.

Other Services

Newer health clubs generally include health-shops, snack bars, restaurants, child-care facilities, member lounges and cafes. It is not unusual for a sauna, steam shower, or wellness areas to be present. Health clubs generally charge a fee to allow visitors to use the equipment, courses, and other provided services.

Facilities and Services

Main workout area

Most health clubs have a main workout area, which primarily consists of free weights including dumbbells, barbells and exercise machines. This area often includes mirrors so that exercisers can monitor and maintain correct posture during their workout.

A gym which predominately or exclusively consists of free weights (dumbbells and barbells), as opposed to exercise machines, is sometimes referred to as a black-iron gym, after the traditional color of weight plates

Effects on Sleep

A 2010 review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the possible exception of heavy exercise taken shortly before bedtime, which may disturb sleep. There is, in any case, insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep

Effects on Depression

A number of factors may contribute to depression including being overweight, low self-esteem, stress and anxiety. Endorphins act as a natural pain reliever and antidepressant in the body. Endorphins have long been regarded as responsible for what is known as "runner's high", a euphoric feeling a person receives from intense physical exertion. However, recent research indicates that anandamide may possibly play a greater role than endorphins in "runner's high". When a person exercises, levels of both circulating serotonin and endorphins are increased. These levels are known to stay elevated even several days after exercise is discontinued, possibly contributing to improvement in mood, increased self-esteem, and weight management. Exercise alone is a potential prevention method and/or treatment for mild forms of depression.

Effects on Brain Function

A 2008 review of cognitive enrichment therapies (strategies to slow or reverse cognitive decline) concluded that "physical activity, and aerobic exercise in particular, enhances older adults' cognitive function".

In mice, exercise improves 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. For instance, it reduces the risk of developing dementia. Furthermore, anecdotal evidence suggests that frequent exercise may reverse alcohol-induced brain damage.

There are several possibilities for why exercise is beneficial for the brain:

increasing the blood and oxygen flow to the brain
increasing growth factors that help create new nerve cells and promote synaptic plasticity
increasing chemicals in the brain that help cognition, such as dopamine, glutamate, norepinephrine, and serotonin

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.^[