**3. Benefits of physical activity**

Overwhelming scientific data has accumulated that demonstrates the significant health benefits linked to regular physical activity [11]. Participants of regular physical activity experience a multitude of physical, psychological, and social benefits.

#### *Physical Activity and Health Promotion: A Public Health Imperative DOI: http://dx.doi.org/10.5772/intechopen.111927*

Physiologically, regular physical activity can improve all systems of the body leading to inter alia improved cardiorespiratory fitness, muscular fitness (including muscular strength and endurance), body composition, flexibility, and balance [14, 15]. Physical activity has even demonstrated to have a positive influence on dietary behaviour [16]. However, health is determined by both the lack of disease and an individual's resistance to pathogenic factors [17]. In this area, physical activity has demonstrated its effectiveness at reducing an individual's risk of developing numerous chronic conditions and diseases [6]. In fact, individuals who engage in insufficient physical activity have a 20–30% increased risk of death compared to individuals who are sufficiently active [3].

Research has also indicated the positive impact on several areas of an individual's psychology. In this regard, studies have been found to demonstrate that physical activity has confirmed beneficial effects on sleep [18], independent function [19], overall mood [18], cognition [20], self-esteem [21], stress [22], and depression [23]. While regular physical activity has demonstrated these effects in both clinical and non-clinical settings, a greater magnitude of improvements has been demonstrated in a clinical environment in those patients with manifest mental illness [24]. It is for this reason that physical activity has a significant role in the management of mental health conditions, such as depression and anxiety [24]. However, it must be noted that studies have shown that in addition to its beneficial effects, excessive physical activity may lead to overtraining and impair mental health specifically generating psychological symptoms that mimic depression [24].

### **3.1 Mechanism of effect of physical activity and physical health**

The improvement of health and prevention of disease depends on the mechanisms of general adaptation and enhanced homeostatic regulation and [25]. In this regard, there are several changes which are essential both for increasing adaptivity and for increased human performance [26]. Such changes that improve health and prevent disease include improvements in immunoactivities such as central nervous regulation and function, increased endocrine system function, higher insulin sensitivity, improvement in the capacity of the oxygen transport system, improvements in oxygen intake, delivery, and usage, increases in metabolic function, increased energy potential, and increases in functional stability [25, 26]. Further, physical activity has direct positive influences on the cardiovascular system including lower systemic blood pressure, increased availability of vasodilatory mediators such as nitric oxide, enhanced myocardial contractility, improved lipoprotein metabolism, enhanced ageing-related calcium distribution leading to an enhanced antisclerotic effect of physical activity, improved diaphragm and respiratory muscle strength increasing air flow through the lungs, reduction of respiratory mucous, and an increase oxygen levels [27–29].

#### **3.2 Mechanism of effect of physical activity and mental health**

Mental disorders are a major public health concern. There are numerous hypotheses proposing the mechanism of the effect of physical activity on mental health [24]. Despite the limited research on the mechanistic effects of physical activity on mental health it is thought that improvements in mental health arise from a combination of both psychological and physiological mechanisms, comprising endorphins, neurotransmitters, and the hypothalamic-pituitary-adrenal axis, and via the thermogenic hypothesis [30].

A possible psychological mechanism by which physical activity may improve mental health is related to the distraction hypothesis. Distraction is proposed to move individuals away and distract them from stressful stimuli and into physical activity [31]. Further, many individuals find physical activity to be psychologically and physically challenging. By overcoming such challenges through it is proposed that an individual's self-efficacy improves, leading to an improved self-confidence and mood [31].

Physiologically, the most well-known mechanism by which physical activity affects mental health is through endorphins, which are endogenous opioids. Specifically, physical activity has been demonstrated to positively impact mental well-being, mood, and common mental disorders and their symptoms through the enhanced release of beta endorphins [31]. It is also thought that physical activity affects mental health through brain monoamines, such as dopamine, norepinephrine, and serotonin, which are the three foremost monoamine neurotransmitters demonstrated to be impacted upon by physical activity [32]. However, different physical activity, and specifically the intensities at which they are performed, may cause varied amounts of feedback in the hypothalamus-pituitary gland-adrenal gland axis and should be taken into consideration when developing physical activity public health interventions for mental health [32]. Another proposed physiological mechanism by which physical activity may positively influence mood is through thermogenesis or the production of the body because of an increased energy production required for the physical activity. It is this thermogenesis, that like a warm bath, is proposed to result in relaxation and a better mood [31].

### **4. Barriers to physical activity**

Thanks to sustained global and national efforts, it is increasingly rare that individuals do not know that physical activity has demonstrable benefits for both physical and mental health. However, despite knowing the multitude of benefits associated with regular physical activity, many individuals still experience barriers preventing them from engaging in physical activity. Barriers can be recognised as either physical, psychological, or socio-ecological.

Identifying the barriers and motivators contribute toward the development of specific physical activity health promotion interventions [33]. Recent studies have suggested that barriers prohibiting engagement in physical activity in adults relate mainly to environmental factors and resources, while motivators facilitating engagement in physical activity relate to health benefits, social influences, reinforcement, and assistance in managing change [33].

As such, physical activity public health interventions should focus on overcoming deficiencies in environmental factors and resources. This could be achieved by for example presenting physical activities in the community, effectively reducing environmental factors, such as the extreme cold weather conditions and limiting street environment indicators [34]. Further, physical activity public health interventions could mitigate the effect of resources by making use of existing resources in the community (i.e., community centers for delivery of interventions) and design appropriate physical activity interventions for use in these facilities based on their low supervisory requirements and cost implications [35]. To ensure the effectiveness of the community- and population wide interventions based on motivating factors, physical activity interventions could promote and objectively monitor the health benefits

associated with the physical activity intervention. With regards to social influences and reinforcement, physical activity interventions should make use of activities such as group, rather than individual, interventions.
