This prospective study is one of few surveys which examines the incidence and characteristics of injuries in top-level futsal players and to our knowledge, is the first one in Asia. According to our findings the incidence rate of injury among futsal players was 2.22 injuries per 1000 players-hours. This finding is in contrast with the study by Junge and Dvorak (
4) which reported 195.6 injuries per 1000 players-hours and also the reported incidence rate of injury in the FIFA World Cups 1998, 2002 and 2006 (mean incidence rate of 74.2 injuries per 1000 players-hours) (
4,
7,
12). This difference might be due to the different level of playing futsal in the FIFA World Cups and Iranian futsal league, besides, in these studies only the injuries incurred during the matches were recorded while we reported all injuries that happened in the matches and training sessions. A major obstacle in the evaluation of the incidence and characteristics of injuries in futsal is that there is no specific consensus for the definition of injuries among futsal players, while standard protocols have been developed for footballers (
18-
21). In previous studies, consecutive absence from training or match has been used as the definition of injury (
19). However, by use of this definition, many chronic and mild injuries will be missed (
20,
21). In this study, we used the definition which was developed by Fuller et al. for footballers (
16). On this basis injury defined as any physical complaint that results from a career related training session or a match, irrespective of the need for medical attention or time loss from sports activities (
4,
21). So, in addition to limited number of studies regarding the injury characteristics among futsal players, comparison between the studies due to the use of different definitions is not possible. This study is one of the very few surveys which compares the incidence and characteristics of injuries between men and women in the top-level futsal players. The results show that the rate of injury is higher in female players than male players (P = 0.001,
Table 2). As it is mentioned before, this significant difference was mostly due to non-contact injuries. The level of fitness of the players is one of the important factors which is highly associated with the risk of sports injuries (
11,
20). Considering the nature of futsal which requires multiple sprints and frequent changes in the direction of movements, the physical fitness factors (particularly speed and agility) of the athletes should be much improved to make the players able to participate in the competitions. Therefore, it seems rational that rate of injury among female futsal players with lower level of physical fitness than men is much more than male futsal players, as is shown in this study (
6,
12,
22). While Junge and Dvorak reported that the majority of injuries in Futsal World Cups were caused by contact trauma (
4), the majority of injuries sustained by the athletes in the current study were due to non-contact trauma. Inclusion of injuries which occurred during training sessions might be considered as a possible explanation for this difference. In the present study, 85.2 % injuries were located at the lower extremities with the ankle being the most frequent location of injury (40.7%). These results are similar to the results that were reported previously for elite football male players (
4,
6,
22). Also, in the study of Junge and Dvorak (
4) the majority of injuries in futsal were observed at the lower extremity, and the most frequent diagnoses were contusions of the lower leg and ankle sprain. Serrano and colleagues (
23) showed that the sprain of the tibial-tarsal joint was the most common part of injury in Futsal (48.8% of total) which is in accordance with the results of our study. As the most important limiting factor in this study, we had to let some players leave the national team camp for some periods to play for their own team in the futsal league. However, whenever they came back to national team camp, the team physicians reexamined them and they recorded every new observed injury. Considering the growing popularity of futsal, further studies in order to evaluate the incidence, characteristics, and cause of injuries in futsal are required (
24-
26). Such studies could be the cornerstone for development of injury-prevention programs, based on the FIFA 11+ prevention program. The incidence of injury in futsal is high and female players in comparison with male players are more prone to be injured especially by non-contact trauma. The ankle is the most frequent part of injury followed by the knee and the groin in all futsal players. In addition, sprain is the most frequent type of injury among Iranian futsal players. More information on injury mechanisms in futsal is needed to develop specific injury-preventive strategies.