Association Football, or Soccer, is the world's most popular sport, with approximately 200,000 professional and 240 million amateur players.1 This popularity has aroused a growing interest in soccer-related injuries, a great deal of research having been carried out over the past few years into risk factors, preventive strategies, management, incidence and severity.2 Among potential risk factors identified are the football calendar,3 playing surface,4 physical effort,5 and players’ skill proficiency.6 However, to the author's knowledge, little comparative evidence has been recorded regarding the influence of a team's competition status (league or division) on injury rate.

In Spain, the top two professional divisions have marked financial differences, a factor affecting sporting performance as well as the level of the teams.7 Traditionally, it has been observed that in the second division the game is strongly based on physical effort and less on technical skills, while the playing surfaces are usually less even. Thus, it could be hypothesized that there is a greater risk of injury for a second division player than for a first division one.

This study examines the frequency and severity of injuries sustained by the same soccer team over two consecutive seasons when it played in the two divisions, before and after promotion.

This is a comparative study between two levels of professional soccer: the Spanish First Division (FD), and Second Division (SD). The original sample consisted of professional players of the “Real Sporting de Gijón Sociedad Anónima Deportiva” whose injuries were prospectively recorded over the 2006–7 (SD) and the 2008–9 (FD) seasons. All players gave written consent.

All injuries were diagnosed by the club's medical staff and recorded by their senior physiotherapist on a specific injury report form designed for the study. The definitions and data collection procedures used followed the recommendations of the consensus statement for football injury studies.2

A recordable injury was defined as an injury received during competition or training that prevented the player from participating in competition or normal training for at least one day. Training exposure was defined as any physical activity carried out under the supervision of the team coach. Match exposure for players participating included all matches in which the team took part during the seasons considered. Injuries were categorized as “minor” (one to seven days), “moderate” (eight to twenty-eight days) and “major” (over twenty-eight days), based on the real (not estimated) length of time that the player took to recover and resume playing. Each injury was also classified according to its nature, location and mechanism or cause. Finally, we collected information on the laterality of the injuries, player position and days lost as a result.

The primary outcome measure was injury incidence (injuries/1000 h of exposure) in training and match play. Secondary outcomes included injury severity and incidences of various injury types. We calculated relative risks (RR) with 95% confidence intervals to compare the incidence of injury between first and second division and by other variables. We also analyzed the incidence of days lost for each season and variable studied.

Statistical analysis was carried out by calculating proportions in the case of qualitative variables and by using the chi squared test for detecting significant differences. For quantitative variables, the mean, median, standard deviation, range and interquartile range was calculated and to detect significant differences was used ANOVA for normality and equal variance and the nonparametric Kruskal-Wallis test in case otherwise.

In the seasons studied, 14 players played only in the second division, 15 only in the first and 11 in both, making a final sample of 40 players (mean age 25.8 ± 4.7 years).

Table 1 shows the distribution of injuries according to the variables studied. Of a total of 101 injuries, 64 (63.4%) were considered minor, 26 (25.7%) moderate and 11 (10.9%) major. The most frequent ones were sprains and strained muscles, which together made up 46.5% of the total recorded. The most common cause was traumatic, which accounted for almost two thirds of the total, the area most frequently affected being the legs.

Table 1. Distribution of injuries according to the variables analyzed.

Table 2 shows the distribution of the incidence of injuries and days lost by type of injury, category and circumstances. Our results appear to indicate a greater incidence of injuries in FD than in SD, in both training and playing, along with more days lost per injury. The incidence of moderate or major injuries during training was three times higher in FD (3.36 vs 1.01; RR = 3.30), as was the total of injuries during match play (52.82 vs 16.01; RR = 3.30). Altogether, total incidence of major or moderate injuries was three times higher in FD and accounted for 61% of all injuries (Table 2). Regarding days lost, the incidence was higher in FD in both training (60%) and matches (30%), the number of days lost per 1000 h exposure being 50% higher in FD (129.60 vs 85.01 days/1000 h exposure).

Table 2. Distribution of the incidence of injuries and days lost by type of injury, category and circumstances.

Bold values are statistical significant date.

Table 3 shows the distribution of the incidence of injuries for each of the variable studied by division, with a noticeably higher frequency of injuries to the legs, sprains and traumatic injuries in FD.

Table 3. Distribution of the incidence of injuries by division.

Bold values are statistical significant date.

The aim of this study was to analyze the incidence of injuries in a single professional football team and compare the influence on it of the players’ professional status (FD or SD). Very few studies have analyzed injury incidence among the players of a single team in different divisions, so the methodology used and the results obtained may be a useful basis for future research of this type.

Overall, our results agree with previous findings regarding a professional footballer's injury profile, confirming the lower limbs as the area most frequently injured,8, 9 that the most common injuries are sprains and strained muscles10, 11 and that over half of the injuries are minor.12 It was also demonstrated that injuries were more frequently sustained on a players’ dominant side and more probably during matches.13 The injury incidence for the group of footballers studied was 8.65/1000 h exposure, very similar to the 8/1000 h reported by Ekstrand et al. in a recent prospective study in which 23 top European clubs were monitored over nine seasons.14 Here it should be stressed that the incidence of injuries in professional football fluctuates with the context and time of the study. For example, Dauty et al., in a recently published study, found an incidence of 4.7/1000 h after monitoring a single team of the French Ligue 1 for 15 years.15 However, one of the latest meta-analyses published on the epidemiology of professional male football injuries shows that injury incidence may be established at around 6.2/1000 h.16

Comparing the influence of professional status, the data gathered here clearly show FD to present a higher injury risk than SD. A priori, this is a surprising result, for it is normally assumed that lower-status players with less technical skill may be less physically fit and that their playing fields may also be worse. Nevertheless, although skill is known to be a determining factor in football injuries6, recent scientific evidence also indicates that more skilled players would appear to have more likelihood of suffering injury.17 On the other hand, data also show that in Spanish football there is no difference between the divisions in the way that the technical staff train the players or in their injury prevention.18 Nor have differences been found in players’ fitness levels.19, 20 It should be added that Spanish football grounds are subject to the same maintenance rules whatever the division.

In the light of this, it could be argued that FD players sustain more injuries because of their fixture list, which is usually tighter, while the aims may mean more stress for players. Nevertheless, some studies would indicate that it is not always the players who play in most matches that are at the greatest risk of being injured.14 It should also be pointed out that overall football exposure was higher in SD. The influence of professional status on the risk of injury is still, therefore, a controversial topic. Hawkins et al. found no differences in their injury analysis between the English Premier League and Championship.13 On the other hand, Nielsen et al. showed that injury incidence, pattern of injury, and traumatology varied among Swedish players participating at different levels of competition.21 In this regard, further research is needed.

A topic that has been largely overlooked in the epidemiology of injuries in professional football is the true level of risk. The cost of treatment and loss of production through time off work have been estimated at about £1 billion each year in Britain alone22 so it is important to take into account the number of days that a player is absent from work as a result of an injury. It has, in fact, been reported that the percentage of muscle injuries sustained by footballers means over 300 man-days lost per season for a professional team,23 which our study bears out regardless of the division. This confirms the fact that workplace injury risk is considerably higher in professional football than in most other sectors.24

The results of this study should be interpreted in the light of certain limitations. Firstly, only two seasons were studied, one in each division, so an element of chance may be present. Secondly, the different objectives of each team, promotion, relegation or staying in a given division, are important. Finally, the composition of the team was different in the two seasons, including a new coach. This is of crucial importance, as the style of play may have altered (not mentioned in the study) and this may have influenced the frequency of injuries. Future research is therefore necessary, involving a longer period of monitoring and more teams, to confirm our findings.

Authors declare that they don’t have any conflict of interests.

Received 27 February 2013

Accepted 14 May 2013

Corresponding author. tania.f.v@gmail.com