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An empirical approach for defining acceptable levels of risk: a case study in team sports
  1. C W Fuller,
  2. C J Ward
  1. 1
    Centre for Sports Medicine, University of Nottingham, Nottingham, UK
  1. Dr C Fuller, Centre for Sports Medicine, University of Nottingham, Nottingham NG7 2UH, UK; colin.fuller{at}


Objectives: To determine acceptable levels of risk in sport and to compare these with values used in occupational settings.

Design: Cross-sectional, questionnaire-based study.

Settings: Seven soccer and 11 rugby union teams.

Subjects: 140 male athletes and 108 male and 100 female spectators associated with soccer and rugby union teams.

Main outcomes: Views on acceptable frequencies with which athletes sustain acute injuries of various levels of severity.

Results: The responses of athletes and spectators were similar, although spectators consistently indicated a higher acceptable frequency of injury than athletes. There were no significant differences in responses as a function of respondents’ gender and age. The results confirmed an inverse relationship between the acceptable frequency of occurrence and the severity of injury, although the relationships identified by the risk-averse and risk-taking minorities within the sample population were widely different.

Conclusion: The mean frequency–severity risk relationship identified by athletes and spectators in soccer and rugby was similar to the relationship routinely used for risk assessments in industry and commerce.

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In order to evaluate and control risks in a consistent manner, it is necessary to have standards that define acceptable levels of risk.1 In industry, risk evaluation is discussed in terms of the balance between the costs and benefits to individuals, organizations, shareholders, and society, or as a requirement to reduce risk to a level that is “as low as is reasonably practicable”.2 3 There may be valid methods of evaluation in high-risk industries, such as nuclear power,4 offshore oil exploration,5 and transport,6 when it is necessary to balance the profit motives of commercial organizations against the interests of employees and society.7 Some people though voluntarily participate in extreme sports8 where, despite the high risks, there are few calls to restrict their freedom of choice to take part in these activities. Athletes’ decisions on participation can be influenced by their personal aspirations, and this is illustrated by, for example, their continued involvement in sport after serious injury,9 use of local anesthetics for pain relief in order to compete while injured,10 and use of performance enhancing drugs,11 despite being aware of the long-term health consequences of these decisions. Although some athletes appear ready to accept risks if they believe the benefits outweigh the costs, Green et al12 showed in a study of experienced Australian skydivers that risk-taking athletes still make rational judgments about whether to accept risks based on the magnitude of the risk.

Risk management is not intended to eliminate all risk from activities, and an adverse event does not mean that the risk of injury was not evaluated correctly.13 Extreme sports will inevitably result in injuries, but, provided that participants are knowledgeable about the level of risk and the level of risk is acceptable to them, there should be no necessity to restrict participation or to introduce additional control measures, as the risks are borne on the whole by the athletes themselves. Team sports, on the other hand, have wider implications because of the added complexities created by the physical contact between players. The role of risk management in sport has been discussed, and the main stages of the process summarized in a sport-specific risk framework.14 15 Stage 1 of the framework identified the intrinsic (athlete dependent) and extrinsic (event/situation dependent) risk factors impacting on athletes. Stage 2 provided an estimate of the incidence and severity of injuries using appropriate epidemiological studies. Stage 3 evaluated whether the level of risk was acceptable to stakeholders or whether additional mitigation measures were deemed necessary. Stage 4 highlighted the need to communicate the risks to stakeholders. General guidance for managing the risks associated with sport has been presented in a number of publications,1618 and some individual elements included in the risk framework have been investigated, such as identification of risk factors,19 estimation of the incidence and severity of injuries,20 21 and evaluation of stakeholder perceptions of risk22 and efficacy of risk mitigation strategies.23

Depending on the specific activities, risks are normally assessed using a quantified, semi-quantified, or qualitative methodology.1 24 25 It would be expected, for the type and level of risks involved, that a semi-quantified risk matrix would be an appropriate approach for most sports activities. The magnitude of the risk is assessed as a function of the incidence or frequency with which adverse events occur and the harm or consequences resulting from these events15; estimated frequencies are usually plotted on the x axis and consequences on the y axis of the risk matrix. Descriptive categories, such as “very unlikely, unlikely, possible, likely, and very likely” and “trivial, minor, moderate, major, and severe”, are used to provide semi-quantified values of frequency and consequence, respectively.1 24 26 The acceptability of a risk is determined by its location within the matrix, and this is normally defined by descriptive categories such as “trivial, acceptable, tolerable, and unacceptable”1 (fig 1).

Figure 1 Risk matrix for assessing acceptable level of acute and chronic injuries.

Despite the fact that quantified estimates of these categories have been proposed for industrial hazards in terms of fatalities,4 the semi-quantified categories commonly used in risk matrices have not been investigated extensively. Although it is impossible to define a universally applicable level of acceptable risk because of the objective and subjective components of the evaluation,27 defining an acceptable level of risk for a specific organizational setting should be achievable by taking account of the views and preferences of the relevant stakeholders. The aims of this paper were primarily to investigate what levels of injury risk in team sports were deemed to be acceptable by athletes and spectators and whether the values reported by athletes and spectators were similar, and secondly to assess whether the risk acceptance values identified by athletes and spectators in a sports environment equated to the standards routinely used for risk evaluation in other organizational settings.


Rugby union is a full-body contact/collision team sport involving 15 players in each team; the nature of the sport28 is such that players require a high tolerance of physical contact. Soccer is a semi-contact team sport involving 11 players in each team; players generally have a lower tolerance of physical contact than rugby players. Both sports are played worldwide: rugby has 96 countries affiliated to the International Rugby Board28 and soccer has 208 countries affiliated to the Fédération Internationale de Football Association.29 The incidence of lost-time match injuries for rugby union is 91/1000 player-match hours,30 which is among the highest of all collision/contact team sports, and that for soccer is 28/1000 player-match hours.31 The investigation was a cross-sectional questionnaire-based study of male players and male and female spectators involved with seven soccer and 11 rugby union teams associated with four universities and three amateur clubs situated in the Midlands and South of England. Researchers contacted male players at these clubs, explained the purpose of the study, distributed questionnaires to individual players, and collected their responses. The researchers also approached male and female spectators in roughly equal numbers on an individual, random basis at the soccer and rugby union matches played by the clubs; the purpose of the study was again described, a questionnaire provided, and the participants’ responses collected.

The questionnaire was first subjected to a pilot study among 10 sports physicians and physical therapists who were also involved with sport as either athletes or spectators. The final questionnaire distributed to the sample population sought information from participants on the following issues:

  • role (athlete/spectator), activity (rugby union/soccer), gender and age

  • views on the acceptable frequency (5-point scale from never (1) to always (5)) with which professional players in their sport should sustain acute injuries of various levels of severity (no lost-time, 1–7 days, 1–4 weeks, 1–6 months, and >6 months absence from playing and training).

The range of injury severities included in the questionnaire was derived from the recommendations for recording injury severity in the international consensus statements for epidemiological studies of soccer20 and rugby union21 injuries; namely, slight (0 days), minimal (1–3 days), mild (4–7 days), moderate (1–4 weeks), severe (>4 weeks). However, the minimal and mild categories were combined, and the severe category was divided into two separate categories of 1–6 months and >6 months, as these revised values were considered to provide a more appropriate assessment scale of injury severity for this study and they were also more compatible with the descriptive values of harm normally used in risk matrices (see fig 2). As in a previous study investigating stakeholder perceptions of risk in motor racing,22 risk was not defined in the questionnaire in terms of real or perceived risk, so that respondents would reflect their own perspectives of risk in their judgments.32

Figure 2 Result from all spectators and all players on the acceptable risk of sustaining acute sports injuries. Solid line, mean for all results; dashed line, mean value plus or minus twice the standard deviation for the distribution of all results.

Statistical tests

The sample sizes33 required to identify statistically significant differences (power 80%; confidence 95%) in the levels of acceptable risk (effect size 0.5; standard deviation of measurements 0.8) identified by subgroups within the sample population (soccer and rugby union; spectators and athletes) were calculated to be 40 in each subgroup. For this reason, the target number of participants set for each subgroup was 45.

Responses to questions of acceptable risk were reported as mean (SD) for the various subgroups within the sample population. The sample population responses were tested for normality by calculating the coefficients of skewness for the distributions; skewness of results was interpreted using the following coefficient values: <0.5, essentially symmetric; 0.5–1.0, moderately skewed; >1.0, highly skewed.34 Provided that the coefficients of skewness were between −1.0 and +1.0, mean responses from subgroups were compared using a two-sample t test; because of the high number of tests involved, significance was accepted at p<0.01.


Table 1 shows the numbers of respondents in each subgroup.

Table 1 Numbers of respondents in each subgroup of the sample population

The mean (SD) age was 23.8 (5.8) years for all players and 27.7 (12.0) years for all spectators. Table 2 shows the mean (SD) responses received from spectators and players for what they considered to be acceptable levels of injury risk in soccer and rugby union.

Table 2 Response scores from players and spectators to questions about acceptable levels of risk, coefficients of skewness for response distributions, and intergroup comparisons of responses

The coefficients of skewness for the distributions of responses shown in table 2 indicate that the distributions varied from essentially symmetric to moderately skewed. The results were therefore considered to be sufficiently close to normal distributions to allow the use of the two-sample t test for comparisons of responses between the subgroups. The intergroup t tests identified statistically significant differences in the responses received for injuries resulting in 1–6 months and >6 months absence from play between soccer players and spectators and between all players and all spectators (table 2); however, the absolute differences in the results were small (<15%). There were no significant differences in the mean responses provided by male and female spectators or in terms of age of all respondents (table 3).

Table 3 Response scores to questions about acceptable levels of risk, as a function of respondents’ gender and age

Figure 2 shows the mean values for the acceptable frequency of injury given by all players and all spectators plotted as a function of injury severity: the solid line represents the best fit to these values, and the dashed lines represent the best fit to the mean value of all the results plus or minus twice the standard deviation.


Athletes normally undertake sport on a voluntary basis with the knowledge that there is a risk of personal injury, and spectators watch sports to experience the risks vicariously.35 Each sport has its own inherent level of risk which is largely determined by the laws of the sport. Although they may not be able to define the absolute levels of risk, stakeholders can normally rank sports in terms of the relative risks.22 Epidemiological studies provide probability–consequence contours for the risks associated with each sport, but these studies cannot define standards that might be considered to be acceptable levels of risk; such standards can only be proposed after eliciting the views of the participating athletes and other relevant stakeholders associated with the sports. Any group of stakeholders will have a range of views about what constitutes an acceptable level of risk; these views will be distributed around the mean value for the group. Those members of the group willing to accept higher levels of risk will return values above the mean and those members willing to accept lower levels of risk will return values below the mean (fig 3).

Figure 3 Theoretical distribution curve for stakeholder views on acceptable levels of risk.

For a normal distribution, 95% of the sample population values fall within two standard deviations (σ) either side of the mean value. The 2.5% of the population with views that fall below the mean minus two standard deviations could therefore be regarded as the “risk-averse” members of the population, and the 2.5% with views that fall above the mean plus two standard deviations value as the “risk-taking” members (fig 3). Risk homeostasis36 and risk compensation13 theories suggest that each person defines his or her own level of acceptable risk and chooses activities that match this propensity to take risks. Hence, risk-averse stakeholders will be predisposed towards low-risk sports, and risk-taking stakeholders towards high-risk sports.

Factors affecting risk-taking behavior, such as age, gender, drug usage, and personality, have been reviewed by Roberti.37 In the present study, although there were statistically significant differences in the views expressed by a few subgroups within the overall sample population such as soccer players and spectators, differences were generally small and no differences were observed in terms of gender or age. This indicated a consistency in the average opinions of players and spectators across rugby and soccer, even though rugby was associated with a higher incidence of injury than soccer. When the mean responses from spectators and players were displayed on a risk matrix, in terms of injury frequencies and consequences, a common boundary between the areas of acceptable and unacceptable risk was defined for the two groups (fig 2). This boundary corresponded closely to the line normally used in risk matrices of this type to delineate the regions categorized as “acceptable” and “tolerable” risk.1 However, when the values representing the risk-averse group (ie, the mean values of risk for the population minus twice the standard deviation) were presented in the same way, the boundary between the areas of acceptable and unacceptable risk shifted to a position that more closely matched the line normally used to delineate the regions categorized as trivial and acceptable risk. On the other hand, for the risk-taking group (ie, the mean values of risk for the population plus twice the standard deviation), the boundary between the areas of acceptable and unacceptable risk moved to a position that matched the line normally used to delineate the regions of tolerable and unacceptable risk (fig 2). Hence, for the risk situation discussed in this study, risk-averse members of the sample population considered the risk to be unacceptable, whereas the risk-taking members of the group considered the risk to be trivial.

What is already known on this topic

  • Acceptable levels of risk are prescribed and routinely used for risk assessments in business and commerce.

  • Levels of risk accepted in most sports are normally determined by the individual behaviors of athletes.

What this study adds

  • For rugby union and soccer, the average levels of acceptable risk identified by athletes and spectators were similar to values used in many occupational activities.

  • The acceptable levels of risk identified by the risk-averse and risk-taking minorities within the sample population were widely different.

Dividing stakeholder views on risk into groups representing the majority, the risk-averse and the risk-taking may have wider applications. For example, it may help to inform debates in occupational and social environments over why conflicts arise with some risk issues but not with others. It can be seen from the discussion presented above that the divergence in opinion of the sample population is related to the standard deviation of the response distribution (fig 3). The relevance of this can be illustrated using two hypothetical scenarios related to the setting of traffic speed limits. In the first scenario, a traffic authority wishes to reduce the speed limit on roads adjacent to schools from 30 to 20 miles per hour. It can be assumed that the standard deviation for the distribution of the public’s views on this issue will be small because the major concern of most sectors of society will focus on the safety of children: in this scenario, there is unlikely to be serious conflict during the decision-making process. In the second scenario, the traffic authority wishes to reduce motorway speed limits from 70 to 60 miles per hour. In this case, the standard deviation for the distribution of the public’s views is likely to be much greater because issues such as safety, vehicle emissions, quality of life, and economics will be considered.38 Differences of opinion on these and other issues will almost certainly lead to conflict during the decision-making process. An interesting area of research prompted by the discussion presented here would therefore be to determine whether the standard deviations (or the coefficients of variation in order to provide a measure of relative difference) of the distributions describing the public’s views on a range of risk issues correlate with the level of public debate generated about each of these issues. If there is a correlation, the approach may provide a useful tool to inform the risk communication process.

Although theoretical investigations of risk evaluation are an important aspect of developing our understanding of the risk assessment process, practitioners are often more concerned about stakeholders’ actual decisions about the acceptability of risk rather than how or why the particular decisions were reached. For this reason, practitioners prefer a pragmatic, rule-based decision-making process, which is one reason why the simple risk matrix approach is used extensively in industry.39 Pidgeon et al27 suggested that appropriate individuals and groups could provide useful information in the debate about acceptable levels of risk. The results presented here indicated that, in the context of sport, athletes and spectators were both capable of providing views on acceptable levels of risk in terms of probabilities and consequences. It is expected that equivalent views would be expressed by athletes and spectators associated with other sports and from other countries where there are similar concerns and debates over societal risk. In addition, the mean views expressed in this study also equated to the values routinely used by “risk experts” to define acceptable levels of risk in industrial and commercial organizational settings. The discussion above shows the importance of understanding that the results obtained from the risk acceptance process must be interpreted with caution because the results may not be universally acceptable, as the conclusions do not reflect the views of either the risk-averse or the risk-taking stakeholders.


CWF was responsible for the original concept for the study, the study design, interpretation of results, and final revision of manuscript. CJW contributed to the study design, and was responsible for data collection, analysis of results, and the draft manuscript.



  • None.