Globally, physical inactivity has been shown to be an independent risk factor for a range of chronic conditions and is one of the major public health challenges globally [1, 2]. Increased physical activity has been shown to lower the risk of coronary heart disease [3-5], type 2 diabetes [6], and hypertension [7]. Despite this knowledge about the benefits of physical activity, physical inactivity and its negative consequences remain a problem worldwide. More specifically, even though communicable diseases, such as HIV and Tuberculosis, are likely persist as the principal health concerns for Sub-Saharan African countries in the near future; non-communicable diseases such as heart disease, diabetes, and hypertension, which are linked to physical inactivity, have become more prevalent [8, 9].

In South Africa, a significant amount of the movement towards obesity and physical inactivity in adults can be accredited to the process of urbanization and associated socio-economic change. There has been a movement away from agriculturally-based economies to cash-based economies and this shift has reduced the need for physical labour and enhanced the need for sedentary or less intensive physical work [8-10]. This is particularly significant as a large amount of the physical activity in which the working class South Africans engage in is through walking for transportation and through physical activities related to their jobs. The levels of physical inactivity, which refers to being engaged in no or very little physical activity at work, at home, for transport or during discretionary time, has been projected to be between 43% and 49% in South African individuals aged 15 years or older [8-10].

Within the context of the above mentioned processes of economic and social change, an improved understanding of the factors associated with physical activity or inactivity is important for the development of effective interventions for promoting regular physical activity in a context of declining physical activity. A variety of factors have been shown to influence the levels of physical activity. These include intrapersonal, interpersonal, organisational, occupational and environmental, social, and lifestyle related factors [10-14].

In South Africa, the understanding of factors of greatest importance in promoting regular physical activity in the general population remains scarce. Studies assessing the prevalence and factors associated with physical activity in the country have largely focussed on specific subpopulations, such as children [15], rural populations [10], and Black women [16]. This study seeks to assess the prevalence and factors associated with physical activity in a representative sample of South African adults. Within these studies of more specific populations within South Africa, McVeigh et al. [15] found that children from low income households and those who had less educated parents were less likely to be physically active. Micklesfield et al. [10] also found that those from lower income households were less likely to be physical active in a sample of rural South Africans. They also found that males had higher levels of physical activity than females. A review by Muthuri et al. [9] found that all of the above mentioned factors influence the levels of physical activity in a review of studies conducted on sub-Saharan children. In addition, they also found that those living in urban areas were less likely to be physically active.

The above studies on eclectic populations within South Africa illustrate the varied contributors to physical inactivity within South Africa. These studies on more specific populations thus offer crucial information. It is however also necessary to get a general sense of the levels and predictors of physical activity and inactivity in South Africa. This study seeks to employ nationally representative data to give this general insight regarding the South African population. Though this study employs self-report data from 2012 [17], it is argued that it still offers crucial information regarding the factors related to physical inactivity in South Africa in general rather than focusing a specific subset of the South African populous. This study employs some of the most recent nationally representative data related to physical activity. It can therefore give researchers a general picture of the state of physical activity in South Africa and offer direction for future, more rigorous research.

The aim of this study was to assess the factors that influence physical activity in a representative sample of South Africans. Although communicable diseases, including HIV and Tuberculosis, remain the primary health concern for South Africa; non-communicable diseases that are exacerbated by inactivity, such as heart disease, diabetes, and hypertension, have become more prevalent [8, 9]. Generally, the results of this study show that less than half of individuals were moderately or vigorously physically active. This is slightly higher than previously estimated levels in South Africa [10]. This is much lower than activity levels reported from other regions such as South-East Asia, the Americas, and the eastern Mediterranean region [12].

The difference between South Africa and these more developed regions could be linked to the fact that development allows for more leisure time and therefore more time to engage in physical activity outside of work [19]. This is linked to socioeconomic status as those of higher socioeconomic strata in developing regions often lead lifestyles comparable to those in developed regions, particularly in South Africa. This study found that those of a lower socioeconomic status are less likely to engage in physical activity. This finding is similar to previous findings in South Africa in studies of children and those living in rural areas [10, 15]. These lower levels of physical activity amongst those of low socioeconomic status may be because these individuals similarly have less leisure time to engage recreational activities such as sport [20]. This is related to the disparities in physical activity observed between more developed and less developed regions. Those living in developed regions are likely to have more leisure time than those living in less developed regions. Additionally, the disparities in physical activity between low and higher socioeconomic status individuals could be explained by a lack of accessibility to training facilities in low income areas [11, 14]. More educated individuals were also more likely to be physically active. This is similar to previous findings amongst South African subpopulations [10, 15].

Previous studies have consistently found that individuals living in urban areas are more likely to engage in physical activity than those living in rural areas. The physical environments of these areas appear to explain these disparities as individuals living in urban areas are more likely to report using neighbourhood streets, parks, and malls as spaces to exercise [21, 22]. This study has shown somewhat mixed results. While individuals living in informal settings where the above amenities are less available were less likely to engage in moderate physical activity, there was no difference in the levels of vigorous physical activity. Additionally, those in other formal settings (farms) were less likely engage in vigorous physical activity than those in formal urban settings. This suggests that the relationship between physical activity and setting may be more complex and more research is needed.

The results showed that older individuals were less likely to engage in physical activity. Several studies, including Hallal et al. [12] (a global review) and Milanović et al. [23] (Serbia), have found similar results. Indeed, this is the most consistent finding in physical activity epidemiology. Age-related declines in physical activity have been shown to be related to biological factors, particularly age-related changes in the dopamine system which controls motivation for movement [24, 25]. In addition, other factors that come with adulthood have also been postulated to influence physical activity. This study found that marriage reduces physical activity, particularly vigorous activity. This is similar to previous findings noting that family changes that occur in marriage, such as having children, are partially responsible for this reduction [26, 27].

The results showed that males were more likely to be physically active. This is similar to previous findings in North America [28], Europe [29], and Asia [30]. These differences have been attributed to gender norms and stereotypes. Even though natural physical differences are present between women and men, they do not sufficiently to account for sex differences the levels of physical activity, social differences also need to be considered. Men and women are argued to internalize social expectations and this informs their reality. Hence, the perception that physically strenuous activities are linked to masculinity motivates men to more readily engage in these activities while women become less motivated to do so [28].

The results of this study showed that those individuals with poor health were less likely to be physically active. This is similar to previous findings that show that poor health can discourage individuals from participating in physical activities [13]. There is ample evidence illustrating the negative consequences of physical inactivity on poor health [31], this suggests that these two facets may serve to reinforce each other over time.

The study is limited by the self-reporting of physical activity, which is not the equivalent of an objective, accelerometry-based assessment. This may introduce a bias due to desirability resulting in over-reporting of physical activity. Self-report can also result in recall bias, which may lead to over- or underestimated physical activity. Nevertheless, the analysis is based on a nationally representative sample and contributes to the evidence base necessary for appropriate interventions in the adult population in South Africa.

The findings show that high levels of inactivity are closely associated with people’s socio-economic position, education, sex, race, and health status. Interventions should be tailored to the disadvantaged communities to maximise their effectiveness. Interventions such as the creation and improvement of access to places for physical activity with informational outreach activities, community-scale and street-scale urban design and land use, and active transport policy and practices could be useful in increasing the ease of access to physical activities and could therefore make it easier for marginalized individuals, such as low-income or ill individuals, to engage in physical activities. Additionally, more methodologically rigorous studies are needed to better understand and improve patterns of health-enhancing physical activity amongst South Africans.