Regular moderate-intensity physical activity, as well as high-intensity activity, makes a positive contribution to health outcomes. Evidence has accumulated to demonstrate that the risk of diabetes, coronary heart disease, and some cancers is reduced in people who are at least moderately physically active (7,11). Accordingly, a physically active lifestyle has recently been described as public health’s best buy (8,14).
Although injuries are known to be a frequent occurrence, little is currently known about the actual incidence rates of injury during physical activity in the general population (4,10). A recent study reported that over a 30-d period, 1.4% of people walking for exercise were injured compared with 0.9% of those who cycled, 1.6% of those who gardened, 1.4% of those participating in aerobics, and 2.4% of those who lifted weights (10). In the UK, Nicholl et al. (9) reported that 25% of a population survey respondents participated in vigorous physical activity during the previous 4 wk and 11% of these sustained some injury or illness during this period. Of the incidents leading to injury, 48% resulted in restriction of further physical activity and 41% resulted in seeking treatment. In a more recent Australian study, 5% of participants in general sport or active recreation activities sustained an injury during this participation over a 2-wk period (4). Twenty-seven percent of injury cases required treatment, and 36% reported an adverse effect of this injury on their performance or participation in sport and active recreation.
A recent review of physical activity determinant studies (11) found a consistent pattern of perceived barriers to physical activity being negatively associated with overall rates of participation. In Australia, it is estimated that at least one third of adults are so inactive that they gain no health benefit and are at increased risk of chronic disease (3). The most commonly reported barriers to physical activity among sedentary Australians are a lack of time (35%), physical inability (24%), and injury (24%) (7). Injury was reported by just under 20% of those in the age group 18–59 yr to be a barrier to being more active and was a barrier for nearly 40% of 60+ yr olds.
If injury or disability is a barrier toward participating in physical activity, and physical inactivity is associated with poor health status, then a better understanding of the distribution and correlates of injury could potentially inform public health strategies. This study examines the prevalence of self-reported injury or disability as a barrier to increased physical activity and the extent to which this varies with age, gender, education level, current physical activity levels, and body mass index in a sample of urban-dwelling adult Australians.
Data were extracted from an urban-representative population survey carried out in late 1990 and early 1991 (N = 2298). All participants provided written informed consent (5). Full details of the survey methodology have been published elsewhere (2,5), and a summary is given here. A sample of adults was drawn from metropolitan Adelaide, South Australia, using a three-stage systematic random sampling procedure generated by the Australian Bureau of Statistics to oversample older people. Stage 1 was a computerized random selection of Census Collectors’ Districts. Stage 2 comprised a random selection of 12 dwellings within each district, with a predetermined skip between selections. Stage 3 consisted of every individual within a chosen dwelling aged 45 yr and older and every second person aged 18–44 yr being selected. Interviews were conducted in the home. During each interview, basic demographic information was obtained on age, gender, and highest educational level attained.
Respondents were presented with a list of 20 common leisure time physical activities on a prompt card and were asked “in the last 2 weeks which, if any, of these activities have you done?” Up to five activities could be identified. Activities included athletics, table tennis, sailing/boating, cricket/football, snow skiing, water skiing, ice skating, lawn bowls, walking, jogging/running, calisthenics, aerobics, weight training, circuits, swimming, bicycling, netball/basketball, golf, tennis, squash, or other. Respondents were also asked to state the frequency, duration, and perceived effort of participation on a four-point scale in each activity. The rate of energy expenditure for each intensity of participation in each activity, in metabolic equivalents, was multiplied by the total time engaged in the activity over the past 2 wk. The resultant values were expressed in kcal·d-1·kg-1. These values were summed across the 2-wk period to represent total energy expenditure. Energy expenditure was then classified into one of four categories: sedentary (<50 kcal·wk-1), low levels of physical activity, (51–799 kcal·wk-1), moderate levels of physical activity (800 or more kcal·wk-1 but not engaging in more than 59 min of vigorous activity per week), and high levels of physical activity (more than 1600 kcal·wk-1 or at least 60 min of vigorous activity per week). Vigorous activity was defined as self-reported activity that made the respondent “breathe harder or puff and pant.”
Height and weight (without clothes and shoes) were self-reported at the time of the interview. Body mass index (BMI) was calculated from height and weight according to the formula: weight/height2. Categories of body mass index were coded according to WHO guidelines: underweight (BMI < 18.5 kg·m-2); acceptable weight (18.5–24.9 kg·m-2); overweight (25.0–29.9 kg·m-2); and obese (BMI ≥ 30.0 kg·m-2).
Respondents were asked “which of these reasons for not exercising (more) applies to you?” They were then provided with a list of 19 barriers to select from including “I have an injury or disability that stops me” and “I might get injured or damage my health.” More than one reason (barrier) could be selected. Other identified barriers have been described elsewhere and included such things as a lack of time, other commitments, or a dislike of physical activity (9). For the purposes of this study, respondents who gave a current injury or disability as one of their reasons for not being more active were identified. The number of people reporting a fear of injury as a barrier toward increased physical activity (106 or 4.6% of the total sample) was too small to permit valid analyses of its relationship to other variables.
Data from 2298 participants were analyzed with the SPSS for Windows Statistical software package. In all analyses, a P-value < 0.05 was considered statistically significant. Chi-square tests were performed to determine whether there was a significant association between reporting of the injury or disability barrier and gender, age-group, education level, BMI category, and physical activity levels. Where there was a significant association, a chi-square test for a linear trend in proportions was conducted (1).
To determine the significant independent factors associated with the current injury or disability barrier, a logistic regression analysis was undertaken. Independent variables included in this analysis were age group, gender, education level, BMI category, and physical activity category, because these were shown to have some relationship with the injury or disability barrier in the bivariate analyses. Logistic regression parameter estimates were estimated using a likelihood ratio estimation procedure, with all variables included in the model. Odds ratios and 95% confidence intervals were computed, relative to a baseline category for each variable. For the purposes of these computations, the baseline categories were taken to be age: 18–29 yr; education level: postsecondary; gender: male; BMI: acceptable weight/underweight; and physical activity: high.
Twenty percent of the total survey population (i.e., 466/2298) reported a current injury or disability as a barrier to being more active. Just over half of these respondents (54.1%) named the injury or disability barrier as their major barrier to increased physical activity. There was no significant difference in the proportion of male and female subjects who reported the injury or disability barrier (20.1% vs 20.5%, respectively). Figure 1 shows a significant bivariate relationship between reporting current injury or disability as a barrier to being more active and age (χ2 (4) = 82.3, P < 0.001). Older respondents were significantly more likely to report current injury or disability as a barrier to increased levels of physical activity than were younger respondents. The test for trend indicated a nonlinear trend in the proportion reporting the injury or disability barrier and age. Respondents who had not completed high school reported the injury or disability barrier (24.6%) more frequently than both those with at least some high schooling (16.5%) and post high-school education (18.4%; χ2 (2) = 21.4, P < 0.001). This trend was not linear.
Figure 2 shows the bivariate relationship between the BMI categories and current injury or disability as a barrier to increased physical activity. The greater the BMI, the more likely the reporting of current injury or disability as a barrier to increased physical activity (χ2 (2) = 30.0, P < 0.001); a significant linear trend was observed in this relationship.
There was a significant linear relationship between current physical activity levels and the reporting of current injury or disability as a barrier to increased physical activity in the bivariate analyses (χ2 (3) = 11.4, P < 0.05). This is shown in Figure 3.
Table 1 summarizes the analyses of the multivariate relationship between the predictor variables and current injury or disability as a barrier to increased physical activity as determined from the logistic regression analyses. All odds ratios (OR) have been adjusted for the effects of the other factors. The only two significant independent factors associated with the current injury or disability barrier were age (P < 0.001) and BMI (P < 0.001). Those aged 50–59 yr (OR = 1.85) and 60+ yr (OR = 2.86) were significantly more likely to report current injury or disability as a barrier than people aged 18–29 yr. Overweight (OR = 1.35) and obese (OR = 2.23) individuals were significantly more likely to report the current injury or disability barrier than were people who were of acceptable or low weight.
Although people categorized as sedentary were also significantly more likely to report current injury or disability as a barrier to increased physical activity than were those who were vigorously active (OR = 1.50), there was no significant overall association between current levels of physical activity and the current injury or disability barrier in the logistic regression analysis, after adjusting for all other variables.
Data from a population representative sample of urban Australian adults were used to examine the relationship between current injury or disability as a reported barrier to increased physical activity and its associations with gender, educational attainment, age, and body mass index. As noted by Powell et al. (10), some people will stop participating in physical activities if they sustain an injury and will not therefore reap the benefits of an active lifestyle.
Increasing age was accompanied by an increased reporting of current injury or disability as a barrier to being more active, independently of increasing body mass index, education level, current physical activity levels, and gender. Uitenbrock (13) found a negative relationship between injury risk and increasing age, as well as a decline in the number of participants who exercised at least once in the previous week. Similarly, Nicholl et al. (9) found that injury rates, per 100 persons, declined after the age of 45 yr. Powell et al. (10) also reported a significantly higher prevalence of self-reported injuries among younger people than older people in a population based study of injuries during walking and gardening. However, because none of these studies adjusted for actual exposure time (i.e., hours of participation), this result is likely to reflect the decrease with age of the amount of time that individuals are actively involved in sport and exercise. There have been very few studies to date that have investigated the relationship between age and exposure-adjusted injury risk during sport and physical activity, particularly in those who are not young. Nevertheless, the evidence points to an increased risk of such injury, and a prolonged healing time after such injury, in older persons (6).
Body mass index was also significantly and positively associated with the self-reporting of current injury or disability as a barrier to being more active in the multivariate analysis. This result is independent of age, gender, education level and current physical activity levels. In a 1-yr prospective study of young adults, each 2-unit increase in BMI was associated with an elevated odds ratio (1.52) of injury risk of injury, after adjusting for other variables including previous injury and total exposure (15). There have been no studies to date that have considered this relationship specifically in older adults. It is possible that overweight people are concerned about an increased risk of injury due to the increased loads on their musculoskeletal system when they have a current injury or disability. Alternatively, people who become more inactive because of a current injury or disability may put on weight as a result of their reduced activity. This issue will remain unresolved until it is investigated in prospective cohort studies.
The association between reported current injury or disability as a barrier with current physical activity levels was not significant, after adjusting for age, BMI, education, and gender. This suggests that current injury or disability has a more direct association with concurrent body weight than with current physical activity levels, reflecting the complex relationship between physical inactivity and the development of overweight and obesity.
It is important that strategies to promote physical activity, especially those targeted at older or overweight groups, give consideration to current injury or disability status. It should be possible to identify relevant patterns of behavior and adopt current injury or disability countermeasures, which may lead to the reduction of injury in older persons and those with chronic conditions (12). Those who are sedentary or overweight should be provided with general preventive approaches to physical activity which will reduce the chance of them sustaining an injury when involved in organized or informal physical activity. Appropriate advice may reduce the short-term impact of injury and establish a basis for the adoption of a longer-term physically active lifestyle.
These findings have relevance to clinical practice. Some form of injury or related disability is likely to be a concern on the part of older and overweight patients who are being advised to become more active. Actual and perceived risk of injury, or discomfort related to musculoskeletal disability, may therefore be important barriers to exercise adoption and adherence. Exercise science practitioners in their dealings with older and overweight patients, may find it helpful to address such issues explicitly and to build appropriate management strategies into prescribed exercise programs.
The results presented here are based upon data from a cross sectional survey of Australians in one urban region. Given the relationship between current injury or disability as a barrier to being more active and both age and BMI identified in this study, more information is needed to determine exactly why some people report this barrier and others do not. Studies are also needed to distinguish the effects on physical activity of actual versus perceived injury and disability as a barrier. Given that older persons, and those who are overweight and obese, are the target of many health promotion campaigns, the relationships observed in this study need to be confirmed by further investigations of other population groups. Longitudinal and prospective cohort studies that reveal the long-term consequences of injuries sustained in formal and informal physical activity particularly are needed.
A/Prof Caroline Finch was partially supported by a National Health and Medical Research Council Public Health Research Fellowship.
Address for correspondence: Caroline Finch, Ph.D., School of Health Sciences, Deakin University, 221 Burwood Highway, Burwood 3125, Victoria, Australia; E-mail: email@example.com.
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