Encouraging and enabling participation in sport, exercise and physical activity requires coherent articulation of the exact nature of each discipline to generate engagement. Clear delineation between these constructs already exists; therefore clarity concerning characterization is essential to promote uptake, especially among inactive individuals.

Physical activity is an umbrella term, of which sport and exercise are two significant and meaningful forms (Fig. 2.1). We propose that physical activity encapsulates the full range of major movements undertaken by any individual, including those not subject to structure or form. According to Bouchard and Shephard [12], physical activity represents any bodily movement produced by skeletal muscle resulting in energy expenditure above a resting level. Clearly, this definition encompasses a wide range of ambulation and movement not related to sport or formal exercise. At the same time, it integrates the pleasure and the health benefits that might accrue from being active through gardening, walking or doing housework. It also includes activity which is incidental to pursuing some other purpose, such as walking to and from work or gardening to grow vegetables for the table. Importantly, the appeal of incidental physical activity should not be confused with upholding any interest in either sport or exercise, or indeed, of even being convertible into such an interest.

It is also important to have a clear understanding of what sport is and how it is defined, so that its overall appeal in a population can be identified. McKenna and Riddoch [13] suggest that sport (a subset of physical activity) comprises structured competitive situations governed by rules. However, it is essential to remember that some activities, considered by their participants and administrators as sports, do not always sit comfortably within this conceptualisation. One of the most contentious issues that impedes the promotion of sport as a health-promoting behaviour is the role that intense competition may play; as compelling as it is for those who enjoy winning and losing, it is equally repulsive to many others who have much to gain from increasing their activity levels.

While exercise can occur as a consequence of participating in sports, it can also be practised outside a sporting environment for its own sake. This differentiates sport from exercise. Exercise is usually seen to be volitional, planned, structured and repetitive with particular fitness-related objectives in mind. It has been described as ‘A form of leisure-time physical activity with a specific external objective, such as the improvement of fitness, physical performance or health (in which the participant is advised to a recommended mode, intensity, frequency or duration of such activity)’ [12].

When assessing physical activity, sport and exercise it is useful for practitioners to be aware of the five basic dimensions—typically drawn from studies centred in the training paradigm—of all physical activities and how they relate to fitness outcomes and to health-related benefits:

Beyond distinguishing the different modes of achieving additional energy expenditure, there are two further relevant and important terms. Worldwide, individuals involved with the task of improving health and fitness will hold distinctive and diffuse understandings of these terms. This highlights the need for clarity and transparency among providers. Despite having independent definitions, the terms ‘health’ and ‘fitness’ are often used interchangeably, which can impede the adoption behaviours of inactive individuals. However, some standard definitions have endured the test of time, and they highlight what additional energy expenditure might contribute to the health of many individuals within society.

Conceptually, health ranges from the narrow technical to the all-embracing moral or philosophical standpoint [14]. In everyday use, health is seen as having positive and negative components. From a negative standpoint, health is simply the absence of disease. Through a positive lens, health represents a state of well-being; complete and optimal physical, mental, social and spiritual functioning. It has been interpreted by Bouchard and colleagues [15] as a human condition with physical, social and psychological dimensions, each characterised on a continuum with positive and negative poles; positive health is associated with a capacity to enjoy life and withstand challenges, it is not merely the absence of disease; negative health is associated with morbidity and, in the extreme, with mortality.

Therefore, health can be considered to be an all-embracing concept; it has objective, subjective and individualised elements, meaning that it cannot be solely measured by objective physical criteria.

In contrast, fitness represents the physical expression of an important element of health. For physiologists—and doubtless many sports coaches—fitness deals specifically with the capacity to perform certain tasks. Also referred to as ‘exercise capacity’ [16], fitness is conventionally thought of in terms of an individual’s capacity to achieve a physical goal. Increased exercise capacity leads to enhanced health status in men and women including improved lipoprotein profiles, carbohydrate metabolism, lower blood pressure and weight loss [17]. Further, the literature highlights the positive effects of aerobic activity on cognitive functioning across the life cycle [18]. This offers another, perhaps overlooked, reason for promoting involvement with physically demanding activities. This may explain why so many lay definitions integrate the notion of mental fitness into their understanding.

Fitness can be achieved through most forms of sport, exercise and physical activity. For example, an older person taking up jogging may experience gains in flexibility and aerobic capacity, e.g. they may be able to stay on a treadmill longer as the workload (speed or incline) increases. Subsequently, they may be able to undertake daily tasks with increased ease and vigour, while also avoiding the negative consequences of sedentary pastimes. Recent research indicates that an increased aerobic capacity can improve cognitive functioning across the life course, adding further reason for promoting involvement in moderate-intensity physical activity wherever possible [19]. There are also indications that in children, fitness is linearly associated with academic achievement and performance [20, 21].

‘Fitness’ is clearly a relative term, and can become ambiguous in lay contexts. Use of the word is shaped by individual needs and desires, and is also dependent upon political, economic, social and cultural contexts. Employees may think of themselves as ‘fit’ if they are simply able to complete their tasks at work. In contrast, an international middle distance runner with a slight injury may be considered ‘unfit’; when they cannot compete at the national championships. To complete our hypothetical loop, a middle-aged obese individual with diagnosed cardiovascular disease who has recently been discharged from hospital, may be described by doctors as ‘fit’ to return to work. The runner is significantly fitter in general terms, but, weighed against his individual needs, has been declared unfit. This distinction sustains two further, though related, concepts: health-related fitness and performance-related fitness.

In summary, health is an all-embracing indicator or expression of a person’s state of being, whereas fitness is one aspect of this which deals with capacity to perform tasks. Neither is solely confined to physical condition, and a crucial contemporary issue is to understand the relative importance of physical activity behaviour over any risks that it might produce [22, 23].

From the earliest recordings of human history, participation in sport, exercise and physical activity has been associated with improvements in health and fitness. This relationship has been further defined by years of scientific research showing a clear causal connection between activity and health status [1]. Equally important, research continues to show that important indices of Public Health are responsive to interventions that successfully support additional energy expenditure in community settings [24]. This has led experts to concur that ‘exercise is medicine’.

One of the earliest studies driving this concept forward involved 31,000 male employees of the London Transport Executive. This study compared the occupational physical activity of bus drivers and bus conductors [25]. The results identified that the more active bus conductors displayed a reduced relative risk when compared to their more sedentary, driver, counterparts. A further groundbreaking study, the Harvard Alumni Study, estimated energy expenditure from self-reported participation in sport, walking and stair climbing [26]. After adjusting the results for age, smoking and hypertension, researchers identified a clear dose-response relationship between increased physical activity and reductions in death due to coronary heart disease. These studies, and others like them, gave us the first empirical insights into the benefits of an active lifestyle, whether based on sports, leisure-time activities or occupational energy expenditure.

Over the past half century, data have been accumulating that being unfit or physically inactive—resulting from a lack of exercise and/or sports participation—has major negative health consequences throughout the lifespan [27]. Being physically active, however this is achieved, is thought to be the best buy for public health and has numerous well-established benefits [28]. These benefits include prevention and reduction of the risk of all-cause mortality, cardiovascular disease, coronary heart disease, stroke, type-2 diabetes, obesity, osteoporosis, poor psychological well-being and mental health, and some cancers [7]. While it is not possible to detail all of these benefits here, we will address the benefits for cardiorespiratory fitness.

We begin by outlining the logic for promoting sports that build cardiorespiratory fitness. Cardiorespiratory fitness is a key component of many effort-based sports, including team sports like football, hockey and basketball and of individual activities like tennis, rowing and cross-country running. Therefore, increasing participation rates in these sports will improve participants’ fitness levels. This, in turn, will profoundly impact on mortality and morbidity rates for those individuals, communities and populations who are most at risk. Yet, the evidence is compelling beyond its face value; it is also vast, robust and consistent [9, 29], as are the relationships between physical inactivity and various health complications [17].

Putting this into a Public Health context, low cardiorespiratory fitness, as an attributable fraction (i.e. the proportion of all health problems or deaths that can be attributed to the risk factor) for all-cause mortality, accounts for more deaths in men and women than smoking, diabetes and obesity combined [27]. Notwithstanding that the death rates associated with physical inactivity are consistent in different populations [30, 31], the association between cardiorespiratory fitness or physical activity and disease holds, even after statistical adjustment for blood pressure, weight loss, lipoprotein profiles, carbohydrate metabolism and other confounding variables [17]. Given this independent effect, data suggest there is something inherently beneficial, although unexplained, to the value of exercise for health [9].

The growing arguments around ‘how much for what benefit’ continue to be refined. This information is probably most relevant for regular, committed exercisers, especially runners. The old maxim that What doesn’t kill you only makes you stronger, is often used, whereas the reality is that mortality benefits are best accumulated by running over shorter distances, specifically <20 miles per week [32]. This research suggests that higher mileage, faster paces, and more frequent running are not associated with better survival. Data indicate a U-shape relationship between all-cause mortality and running, with longer weekly distances trending back toward reduced mortality benefit. These data confirm the value of exercise prescription based on notions associated with training, while its complexity may explain why so few health practitioners willingly engage with activity promotion at a level beyond ‘Do some’. This, along with their access to communities underserved by conventional activity-promoting services, makes them especially well placed to promoting physical activity, and possibly exercising, leaving the promotion of specific doses of exercise to specialists.

However, the logic of altering physiological function to improve health can also be applied to domains beyond sport. Other work has confirmed the cardiovascular protection afforded by occupational activity [25, 26] and of a ‘lifestyle’ approach to being active [7]. Given the rise of sedentary occupations, there is a growing need for sport, exercise and physical activity that are structured and performed for a specific reason. While there is evidence that higher intensity exercise will optimise fitness and health gains [33–35], this intensity is harder to sustain both within an exercise bout and through longer-term involvement. Thus, it is appealing to fewer people and, possibly, most attractive to those who self-select to this intensity. While these individuals may enjoy better health than less active individuals, public policy is rarely based on these groups. Worse, understanding about inactive people suggests that when expectations exaggerate the exertion required for even a modestly successful engagement, they can deter even a try-out, let alone sustained engagement.

Instead, in many countries, including the United Kingdom and United States, regular moderate-intensity activity is promoted. The thinking is that more people can sustain this level of involvement, meaning that this will have a stronger Public Health impact. All things considered, it is important to acknowledge that even though high-intensity training may offer optimal cardio-protection in some instances; this is difficult for most inactive adults to sustain. Indeed, there is considerable evidence that the biological markers of high exertion are such that they can be interpreted negatively [32]. This experience can result in increased attrition from sport, exercise or physical activity interventions, making it almost entirely counter-productive at a population level. The intensity and prescription have to be matched to the needs and abilities of the individual.

These issues are important when the idea of becoming more active is discussed. They are, potentially, even more sensitive when broached in the context of being unwell or experiencing a disease. In countries like the United Kingdom and the United States, General Practitioners and Physicians are often in the frontline of the exercise prescription process for individuals in this situation. However, recent research from the United States [36] showed that physicians advised just over one-third of patients to begin or continue to do exercise or become more physically active. Even though these figures represent a 10 % increase since 2000, and notwithstanding that some patients will be unsuitable for an exercise prescription, most patients who can benefit from increased physical activity are still not being encouraged to undertake it.

Even though the reasons are unclear—and solutions even less obvious—this process is also differentiated, with groups being more or less likely to be encouraged to undertake activity. For example, at every measurement point [36]; women were more likely than men to have been advised to become more active. The percentage of adults advised to exercise increased with age up to 64 years, and then declined. Adults aged 18–24 had the smallest increase in rates of being advised to become more active, and since 2000, remained the age group receiving the least encouragement. Further, and potentially because of its ubiquity and of the particular value of physical activity in remediating its effects, adults with diabetes were more likely than individuals with cardiovascular disease, hypertension and cancer to have been advised to exercise. Lastly, obese adults were almost twice as likely as individuals of a healthy weight to have been advised to undertake exercise or physical activity.

Collectively, this suggests that medical practitioners appreciate that exercise really is medicine, and while the practice of promoting physical activity is on the increase, it remains a reactive—and not a universal—approach. It also hints at a lack of appreciation of the value of preventive intervention based around physical activity, exercise and/or sport. These figures also confirm that considerable ground has to be made up to ensure that physical activity is prescribed to all who have the capacity to engage. Here the challenge is to acknowledge the determinants inherent to the ‘tough sell’ of what advocates clearly see as a ‘best buy’ [37]. In the context of most health systems being able to fund fewer doctors and nurses, the capacity of these systems for achieving widespread adoption of sport, exercise and/or physical activity must be questioned.

An old epidemiological adage suggests Ain’t no effects without side effects; this applies to every Public Health initiative that encourages participation in sport and moderate-intensity exercise and/or physical activity. This is linked to the overall aim of optimising well-being while managing the risks that emerge while pursuing progress—typically achieved by manipulating exercise intensity [3]. Therefore, it is important to remember that, just as the health benefits accrue from increased participation, so too do the associated risks.

While the risks of participation in low-to-moderate-intensity activities are relatively small [38], more vigorous pastimes—including sports participation—bring elevated risk profiles, regardless of an individual’s athletic ability [9]. Sports injuries can be severe and cause significant discomfort, disability, and reduced short-term productivity. They can also be responsible for substantial medical expense, whether or not this is acknowledged by event organisers or by participants. The working rule seems to be that the more demanding and vigorous the activity, the more demand is placed on the body, which increases the risk of injury. Unsurprisingly, activities involving physical contact with others are associated with higher than normal rates of contact-related injuries, while repetitive activities bring higher rates of injury linked to repetition.

From the F.I.T.T. acronym (frequency, intensity, time, type; see above) that underpins exercise prescription, intensity represents the major injury risk factor emerging from involvement in sport and exercise. While more vigorous forms of exercise and sport are characterised by increased risk of sudden cardiac arrest, this remains a relatively rare feature [38], even allowing for the media attention that it can sometimes secure. It is also especially rare in young athletes, but where it does occur seems to be linked to previously undiagnosed hereditary congenital cardiovascular disease. While pre-screening remains contentious, there is some evidence of its capacity to prevent harm [39, 40]. Given these potential complications, gauging the depth of such problems is a requirement for any individuals promoting sport and physical activity. With distinctive demands, each activity and sport has its own injuries and injury mechanisms; therefore, it is beyond our scope to discuss specific sports in full detail. However we will discuss general issues affecting musculoskeletal injury and sudden cardiac death.

The risk of musculoskeletal injuries increases with intensity and with the volume of the activity. It is important that engagement is managed to allow for sufficient recovery between training sessions. Even starting a walk–jog programme will require days of rest between sessions to ensure adequate recovery, especially among people with long histories of inactivity. For people engaged with competitive sport, it is also important that practice sessions—which tend to be more directly linked to competitive elements of performance—are also regulated carefully. At the start of any new programme, it is important to understand the motivational significance of undertaking a session without having recovered from a previous session. The well-known phenomenon of delayed onset of muscle soreness (DOMS) , which emerges within 24 h of exercising and can last up 5 days post-exercise, can profoundly affect enjoyment and/or satisfaction [41]. This, in turn, will affect the likelihood of subsequent engagement, depending on how each individual places meaning on these symptoms. Staff who grasp the close interconnection between bodily symptoms and motivation are differently suited to promoting physical activity to newcomers compared to those who only appreciate the sequence and timing of biological adaptation.

Research suggests that physically active adults tend to experience a higher incidence of leisure-time and sport-related injuries than their less active counterparts [42]. Jogging is perhaps the most frequently endorsed way of becoming more engaged with exercise and even this mild form of exercise carries risk. Injury incidence per exposure (which covers the full range of experience) varies from 7 to 59 per 1000 h of running [43–45]. However, in the only study assessing novices’ preparation to complete a 4-mile (6–7 km) event [46], 21 % of the 532 (306 women) runners had at least one running-related injury. Among these novices the incidence of running-related injury per 1000 h of exposure was 33 (95 % CI, 27–40), and the number of injured participants was 20.6 per 100 runners. Given this markedly high incidence of injury in novice runners, the potential for effective preparation prior to engagement, including muscle strengthening and preventative interventions, is high.

Interestingly, adults who meet the current physical activity recommendations by performing moderate-intensity activity have an overall musculoskeletal injury rate comparable to inactive adults [47]. While the injury rate reported among active men and women during sport and leisure-time physical activity is higher compared to their rates while not undertaking these activities, inactive adults report more injuries during the extensive time they spend in non-sport and non-leisure-time activities. For exercisers, this lower injury incidence during non-leisure time may be attributed to their increased fitness levels—including increased endurance, strength and balance [48]. Given that injury—even just the fear of injury—is one of the primary reasons for not engaging in activity and sport, this research suggests that leading a physically active lifestyle is no more likely to result in musculoskeletal injury than living a sedentary lifestyle. Moreover, if undertaken appropriately, leading an active lifestyle can generate a range of physiological, psychological and psychosocial benefits [7] that will not be attained by sedentary individuals.

As with musculoskeletal injuries, the risk of sudden cardiac arrest (or myocardial infarction) is low in asymptomatic—or undiagnosed—adults during moderate-intensity activities [49]. However, and this must be recognised, vigorous exercise carries a transient increase in sudden cardiac death [50], and the greatest risk is found in people who do not habitually perform vigorous exercise [46, 51]. This risk is especially elevated when these habitually sedentary individuals also have latent or documented coronary artery disease [52]. For example, a 50-year-old man with risk of sudden cardiac arrest who performs vigorous exercise or sport, will increase his risk 100 times during the activity; further, this risk remains elevated for an hour post-exercise [6]. This contrasts to the situation of the individual who regularly performs vigorous exercise such as running for one or more hours per week. In this case, the individual would have a 42 % lower baseline risk of having the event, and a lower risk for exercise-associated cardiac arrest. Further, the relative risk of myocardial infarction during vigorous exercise, compared with that at all other times of the day, is 56 times greater among men who exercise infrequently and only five times greater among men who exercise frequently [53].

Although absolute numbers of sudden cardiac deaths during exercise are low, screening—provided by simple instruments like the Preparation and Readiness for Exercise Questionnaire (PAR-Q) [54]—will provide important information about the possible risk. Measures to prevent harm should not stand alone; they are most effective when integrated into a sequence of prevention. Importantly, and notwithstanding the value of subjective estimates of risk (e.g. ‘that surface looks a bit bumpy, so if we run on it, we might risk some ankles being turned’) it is important that provision and practice is developed and refined using more systematic approaches. For effective injury prevention, risks must be identified and described—epidemiologically—in terms of incidence and severity, and the factors and mechanisms that play a part in the occurrence of injuries have to be identified. Practitioners should look to introduce measures that are likely to reduce the risk or severity of injuries. Finally, the effect of the measures must be evaluated by repeating the first step which will lead to a time trend analysis of injury patterns. Ultimately, the evidence that the benefits of participation in sport, exercise and physical activity outweigh the risks is unequivocal [38]. Yet, knowing the risks associated with them is important to help minimise the risk, in order to maximise the benefits.

The London 2012 Olympic and Paralympic games captivated the United Kingdom and a global audience. No doubt it will have inspired some individuals, determined to emulate their heroes, to get into sport. It is highly likely that this involvement positively influenced their health. However, whilst global sporting events like this can cause a significant short-term surge in sports participation levels, maintaining long-term enthusiasm and engagement is more problematic [55]. Fundamentally, without the necessary infrastructure and encouragement, any claims about ‘legacy’ relating to the public health benefits of such sporting spectaculars have questionable veracity. To contribute to better public health, and to deliver on claims that sport is part of generating a healthier community, the challenge is to deliver a long-term step change in the number of people who regularly engage in sport. With the relatively limited appeal of sport across the community, it makes sense that attention also falls to the different constituencies who are more attracted to exercise and to physical activity.

Since 2006, in the United Kingdom there has been a 1.4 million increase in people playing sport at least once a week; the total of people engaged is now 15.3 million. With a population in excess of 60 million, the relative appeal begins to become clear. However, this figure looks even less impressive when the number of people engaged 3 or more times per week is identified—7.3 million. This confirms that most adults, 53.2 %, still play no sport at all, while relatively few are firmly committed [56]. Levels of physical activity are equally concerning; only 4 in 10 men and 3 in 10 women in the United Kingdom meet recommended physical activity guidelines by participating in 150+ min of weekly moderate-intensity physical activity [5]. This figure reduces further when adults 65+ years are considered [7]. With similar profiles reflected worldwide [57], it is unsurprising that physical inactivity is a major public health problem of the twenty-first century [58].