CLINICS 2011;66(10):1707-1712 Model for epidemiological studies on professional soccer player Arliani GG et al. Table 2 - Characteristics of the studies selected for final inclusion. Type N Period Contact person Manual Injury/1000 h Age Exposure factor National/Reserve Hagglund et al; 2006 Azubuike & Okojie; 2009 Walde´ n et al; 2005 Paus et al; 2003 Paus et al; 2003 Cohen et al; 1997 Kucera et al; 2005 Selistre et al; 2009 Palacio et al; 2009 Yoon et al; 2004 Martinez & Villani 2003 Ladeira 1999 P – Prospective. T – Transversal. R – Retrospective. N - Number of individuals. Y – Yes. N – No. - Non available. h - hours of exposure. I – Individual. NI - Non individual. P 263 2 seasons T 196 1 season P 266 1 season P 376 2 seasons P 86 7 seasons R 200 3 seasons P ND 3 seasons T ND 6 days P 30 2 seasons T 411 2 seasons R 656 7.4 seasons P 62 6 months Y Y Y Y Y Y N Y N N Y N N N N N N N N N 9.4 1.42 9.1 128.1 141.8 13.4 17-39 16-19 17-37 16-40 16-19 16-20 18-35 average 22 ,20 average 24.8 I I I I I I NI I I I I I Y Y Y Y The start of data collection for the study requires that a questionnaire must be submitted by each athlete prior to the start of the season. This questionnaire should include the height, weight, body mass index (BMI), position, age, years of professional experience, dominant leg, history of pre- vious injuries, number of games played during the previous season, and previous surgical history of each player. Other information, including flexibility, goniometry, lower limb proprioception, and podoscopic examinations can be added to the questionnaire. It is important to evaluate the flexibility of the quadriceps and hamstring muscles during the preseason to identify soccer players with a high risk of developing muscle injuries during the regular season.18 The flexibility of these muscles can be goniometrically measured bilaterally because previous studies have shown good validity and reliability with this method.21,22 Appraising proprioception in the lower limbs is also important because a previous study revealed differences in the dislocation of the center of gravity and changes in postural balance in soccer players who had undergone ACL reconstruction.19 The history of previous injuries reported by the player should be divided as follows: no previous injuries, a single report of a previous injury, and a history of two or more previous injuries.15 At this moment, athletes should be asked to provide written informed consent. Each athlete’s exposure to injury must be individually recorded either weekly or every two weeks and should cover all training and games. It can be helpful to use a table with the name or code of each player and his or her exposure time (in minutes) for games and practices. Other information, such as the field surface, the temperature and weather conditions during the game, the amount of time spent traveling, the type of training performed, and the game site (home or visitor), should be included in the record. Travel by athletes will be ranked according to the distance traveled in kilometers (km) on the outward journey from the club’s city to the city where the game will be held. Trips will be classified into one of three categories based on distance as follows: short distance (,500 km), medium distance 1709 (between 500 and 800 km), and long distance (.800 km). These distances will be calculated using the method that was used for the Series A 2010 Brazilian Championship, calculating the total distance that the athletes traveled to the games during the tournament. This distance was divided by the total number of trips, and the average distance was 818 km for the outward journey. We used this number as the basis for the above classification for travel within the large Brazilian territory. We will also calculate the travel time (in minutes) for players. Travel time is defined as the number of minutes spent by each player traveling between their home club and the hotel in the city of the game added to the time spent on their return trip. If athletes do not return to their home club but travel to another city for a game, the travel time will be computed as the time required to travel from one hotel to the next. Travel is divided by distance and time, because clubs utilize different means of transportation due to financial circumstances and preferences. Injuries should be recorded by the date of injury, injury type, location and severity, and setting of injury occurrence (i.e., a training session or game). The injury protocol may contain a field with the required exams and final diagnosis. More information can be included in this record, including weather conditions at the time of injury, the surface, the injury mechanism, the time at which the injury occurred, the field location where the injury occurred, and whether the referee called a penalty on the play in which the injury occurred (if the injury was due to contact with another player). One study reported that referees recog- nized infractions in only 47% of cases.20 Recording the playing time when the injury occurred during the game is important because the highest injury risk was found to occur during the first and last 15 minutes of the game.21 Ethics All study participants signed an informed consent docu- ment, and an Ethics Committee reviewed and approved the study.