Since 1985, terms like physical activity, exercise, fitness training, training, fitness and physical fitness are often confused with one another and sometimes they are used interchangeably (1–4). The rapid socio-economic and demographic mutations, the need to benefit from the natural dimension has led to a diversification of the application of physical exercise/sport that today it presents itself with different objectives and with the research of different forms of satisfaction. Thus decreasing the demand of organized sport, competitive racing and the increase of individualized physical activities, aimed to achieve different objectives such as inner balance or psychophysical well-being. The phenomenon of physical exercises or commonly defined as “fitness”, “exercise”, “conditioning”, “resistance training” or better “fitness training”, however, is a very complex reality. Indeed, with the term fitness, it is possible to identify a range of activities that are conducted every day in fitness centers (Gyms) and we can regroup them into Gym resistance training activities; Group fitness activities; Functional fitness activities.
In the last decade, the activities that undergo the term Fitness have evolved. Initially aerobics, step aerobics, jogging, conditioning and bodybuilding were the most common gym activities that enabled population to “be fit”, now we may found more diversified and more careful to the needs of active and non-active population activities. Some examples are: funky, zumba, fit box, cycling activities, calisthenics based training, cross fit, suspension training, kettlebell training, total body conditioning, core training, boot camp, functional training, pilates, yoga, stretching. It is clear that including such activities under the more generic term fitness or fitness training, a psychological process starts in people’s mind that day after day mutates the meaning of the term itself (5–7). There are various definitions of fitness (8), that go from an ability to perform daily activities with vigor, to a demonstration of traits and capacities that are associated with a low risk of premature development of hypokinetic diseases (e.g., those associated with physical inactivity). Although, when we speak about fitness we include the state of wellness that is defined as a multidimensional state of being describing the existence of positive health in an individual as exemplified by quality of life and a sense of well-being (9–11).
Consistent with this definition, there is no doubt that there is a strong relationship between physical fitness and many components of wellness. However, physical fitness is neither health, nor wellness. There is considerable evidence that physical fitness, and the behaviors that build it, can reduce risk of illness and early death (5, 10, 12, 13). In addition, fitness can lead to enhanced cognitive functioning and can enhance one’s ability to participate in leisure, often a satisfying social experience. However, both health and wellness are much broader terms than physical fitness. Poor health can occur even in highly fit people because of factors beyond personal control such as hereditary conditions or conditions caused by bacterial/viral infections. A low fitness level is widely associated with hypokinesia (5, 7). This is a risk factor for various diseases such as coronary diseases, diabetes, metabolic syndrome, hypertension and hypercholesterolemia. Although, inactive people develop a RR due to CHD that is similar to those who smoke cigarettes, have hypertension and have hypercholesterolemia (14, 15). This is just one of the countless examples that confirm that regular exercise represents an important factor in prevention against disease, that are most often associated with death in industrialized countries.
Analyzing various populations that go from youth to elderly, from health to pathological conditions, from specific to recreational fitness users, we will try to answer to some questions such as what benefit fitness training have on health? Or which is its preventive role? And witches are fitness’s major implications? And more in general, what is fitness training?
All the studies included in the review were fitness or health based and had to provide specific information regarding all the questions that this review is trying to answer and updating the original review of the authors. The majority of the cited studies were published from 2006 to 2014 and the ones with a previous date than 2006 were included only if scientific literature did not provide, for that period, pertinent evidence.
The scientific databases used were MEDLINE-NLM and MEDLINE-EBSCO. We also searched on Scopus Elsevier, Cochrane, DOAJ, CASPUR, SciELO, and PLOSONE.
The standardized search strategy included the use of the terms “exercise”, “exercise training”, “fitness training”, “health”, and “fitness” in the title, abstract, and keyword field. We searched also the most common diseases related to physical inactivity (diabetes, metabolic syndrome, stroke, atherosclerosis, hypertension and obesity). Statements and Books were included, when appropriate. The overall research has produced 7737 results but the inclusion criterion has skimmed results to 117 items. Of this after careful analysis, only 92 were inserted in text. The 25 studies not included even if matched the inclusion criteria (year, relevance) were evaluated as “off-topic” in respect to this search. All the selected articles were then divided in 4 major categories: 1) Children and adolescents fitness levels; 2) Fitness training in elderly; 3) Pathology prevention through fitness training; 4) Training through Fitness activities.
Children and adolescents fitness levels
The American Physical Therapy Association SoP (18) has developed a task force to summarize fitness guidelines for children and adolescents. These state that to promote overall fitness, youth should participate in 60 minutes or more of physical activity every day, and that physical therapists should apply research relevant to health-related physical fitness when treating youth, promoting fitness, health, and wellness (19, 20). A high fitness level, in this specific case cardiovascular fitness, can improve quality of life and make ordinary tasks such as street crossing easier (21). A number of 13 highly fit children and 13 low fit children aged 8- to 10-yr-old were tested on a treadmill that was integrated with an immersive virtual world. Child pedestrians crossed the street while undistracted, listening to music, or conversing on a hands-free cellular phone. Cell phones impaired street crossing success rates compared with the undistracted or music conditions for all participants, a result that supports previous research. However, individual differences in aerobic fitness influenced these patterns. Higher-fit children maintained street crossing success rates across all three conditions, whereas lower-fit children showed decreased success rates when on the phone, relative to the undistracted and music conditions. The results suggest that higher levels of childhood aerobic fitness may attenuate the impairment typically associated with multitasking during street crossing; these evidences are also confirmed earlier (21, 22). Furthermore, a low level of fitness in youth can lead to obesity-insulin resistance and diabetes type 2 (22, 23). Intensive exercise training may improve insulin sensitivity. Authors (24) have investigated on this phenomenon in 13.0±1.9 years old subjects, and tried to understand the involved mechanisms. Fasting laboratory studies (insulin, glucose, lipid profile) and assessments of fitness, body composition, skeletal muscle oxidative phosphorylation and intramyocellular lipid content (IMCL), were performed at baseline and study completion. Change in fitness was related to change in insulin resistance in response to lifestyle modification and exercise in obese children. IMCL increased with exercise in these obese children, which may reflect greater muscle lipid oxidative capacity.
Other studies have investigated on the relationship between Aerobic fitness and the adiposity in 8 and 12 year old overweight boys. The results confirm the previous analyzed study’s findings; those with a lower percentage of adiposity had a greater level of aerobic fitness (25, 26). Further intervention has been performed on 99 African and Hispanic girls and their mothers (27). The girls attended a daily exercise, nutrition education, and counseling sessions from 9:00 a.m. to 5:00 p.m. Mothers attended 2-h weekly exercise, nutrition, and counseling sessions. Findings indicated statistically significant reductions in percent body fat, abdominal fat, and 1-mile run/walk minutes indicating the effectiveness of increasing fitness level even in young girls. These findings let us understand that not only there is an improvement on insulin sensitivity or muscle lipid capacity, but this leads to a reduction of body fat that is an important factor for quality of life and self-esteem (28, 29). Two decades ago changes in eating habits does not seem to have influenced the prevalence of obesity in the UK population whereas there seems to be a correlation between hours of television a week and obesity, so it is evident an interesting link between obesity and hypokinesia (30). This section supports the idea that the improvement of physical fitness during childhood is determinant for the future pathologies prevention. As we will see more forward on this review, the fitness training may represent valid support against inactivity, overweight and obesity