This art icle was downloaded by: [ Hong Kong I nst it ut e of Vocat ional] , [ del wong] On: 15 June 2012, At : 02: 15 Publisher: Rout ledge I nform a Lt d Regist ered in England and Wales Regist ered Num ber: 1072954 Regist ered office: Mort im er House, 37- 41 Mort im er St reet , London W1T 3JH, UK Journal of Sports Sciences Publicat ion det ails, including inst ruct ions f or aut hors and subscript ion inf ormat ion: ht t p: / / www. t andf online. com/ loi/ rj sp20 Inj ury rates in professional soccer players during Ramadan Karim Chamari a , Monoem Haddad a , Del P. Wong b , Alexandre Dellal c & Anis Chaouachi a a Tunisian Research Laborat ory “ Sport Perf ormance Opt imisat ion” , Nat ional Cent er of Medicine and Science in Sport s (CNMSS), Tunis, Tunisia b Technological and Higher Educat ion Inst it ut e of Hong Kong, Hong Kong c Olympique Lyonnais FC, Lyon, France Available online: 15 Jun 2012 To cite this article: Karim Chamari, Monoem Haddad, Del P. Wong, Alexandre Dellal & Anis Chaouachi (2012): Inj ury rat es in prof essional soccer players during Ramadan, Journal of Sport s Sciences, DOI: 10. 1080/ 02640414. 2012. 696674 To link to this article: ht t p: / / dx. doi. org/ 10. 1080/ 02640414. 2012. 696674 PLEASE SCROLL DOWN FOR ARTI CLE Full t erm s and condit ions of use: ht t p: / / www.t andfonline.com / page/ t erm s- and- condit ions This art icle m ay be used for research, t eaching, and privat e st udy purposes. Any subst ant ial or syst em at ic reproduct ion, redist ribut ion, reselling, loan, sub- licensing, syst em at ic supply, or dist ribut ion in any form t o anyone is expressly forbidden. The publisher does not give any warrant y express or im plied or m ake any represent at ion t hat t he cont ent s will be com plet e or accurat e or up t o dat e. The accuracy of any inst ruct ions, form ulae, and drug doses should be independent ly verified wit h prim ary sources. The publisher shall not be liable for any loss, act ions, claim s, proceedings, dem and, or cost s or dam ages what soever or howsoever caused arising direct ly or indirect ly in connect ion wit h or arising out of t he use of t his m at erial. Journal of Sports Sciences, 2012; 1–10, iFirst article Injury rates in professional soccer players during Ramadan KARIM CHAMARI1, MONOEM HADDAD1, DEL P. WONG2 ALEXANDRE DELLAL3, & ANIS CHAOUACHI1 1 Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 Tunisian Research Laboratory ‘‘Sport Performance Optimisation’’, National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia, 2Technological and Higher Education Institute of Hong Kong, Hong Kong and 3Olympique Lyonnais FC, Lyon, France (Accepted 21 May 2012) Abstract Many of the socio-cultural lifestyle and dietary changes that take place during Ramadan may affect the risk of injury in athletes, but little evidence is available. The aim of the present study was to examine the effects over two consecutive years of the holy month of Ramadan on injury rates in 42 professional players of a Tunisian top-level professional soccer team. Players were retrospectively organized into fasting and non-fasting groups and monitored for 3 months: 4 weeks before Ramadan, during the month of Ramadan (4 weeks), and 4 weeks after Ramadan each year. During Ramadan, training started at 22.00 h. The circumstances (training/match) and mechanism of injury (traumatic/overuse) were recorded. No significant differences between the three periods were observed for weekly mean training load, training strain, training duration, and Hooper’s Index (quality of sleep, and quantities of stress, delayed-onset muscle soreness, and fatigue). Compared with non-fasting players, fasters had a lower (P 5 0.05) Hooper’s Index and stress during and after Ramadan. No significant difference in injury rates was observed between fasting and non-fasting players. Nevertheless, the rates of noncontact (6.8 vs. 0.6 and 1.1) and training overuse (5.6 vs. 0.6 and 0.5) injuries were significantly higher in fasting players during the month of Ramadan than before or after Ramadan. In conclusion, Ramadan, along with the corresponding changes in nutritional habits, sleeping schedule, and socio-cultural and religious events, significantly increased overuse and non-contact injuries in fasting players despite the fact that the training load, strain, and duration were maintained. Keywords: Religious fast, fasting soccer players, football, injury prevention Introduction Risk of injury is a serious concern for soccer players and clubs in terms of health, performance, and cost. Recently, Ekstrand and colleagues (Ekstrand, Hagglund, & Walden, 2011) conducted a prospective cohort study in which world-class soccer teams (the first team squads of 23 teams selected by the Union of European Football Associations as belonging to the 50 best European teams) were followed for seven consecutive seasons (i.e. 2001 to 2008). The authors identified 4483 injuries that occurred over 566,000 h of exposure (i.e. 475,000 h of training and 91,000 h of match-play), giving an incidence of injury of 8.0 per 1000 h. The incidence of injury during matches was higher than in training (27.5 vs. 4.1; P 5 0.001). A player sustained on average two injuries per season, thus a team with a typical squad of 25 players can expect about 50 injuries each season. Traumatic injuries and hamstring strains were more frequent during the competitive season, while overuse injuries were more common during the pre-season. Training and match injury incidences were stable over the 8-year period with no significant differences between seasons. Injury rates in training and match-play in the study of Ekstrand et al. (2011) were consistent with the data of Hawkins and colleagues (Hawkins, Hulse, Wilkinson, Hodson, & Gibson, 2001), who reported an average of 1.3 injuries per player per season in English professional soccer. In the Swedish Premier League, Hagglund and colleagues (Hagglund, Walden, & Ekstrand, 2006) prospectively recorded individual exposure and time-loss due to injuries over two full consecutive seasons (2001 and 2002). They showed that training and match injury rates were similar between seasons (5.1 vs. 5.3 injuries per 1000 training hours and 25.9 vs. 22.7 injuries per 1000 match hours, respectively), but the analysis of injury severity and injury patterns showed variations between seasons. In a prospective study in Norway, Andersen Correspondence: Del P. Wong, Technological and Higher Education Institute of Hong Kong, Tsing Yi, Hong Kong. E-mail: delwong@alumni.cuhk.net ISSN 0264-0414 print/ISSN 1466-447X online Ó 2012 Taylor & Francis http://dx.doi.org/10.1080/02640414.2012.696674 Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 2 K. Chamari et al. and colleagues (Andersen, Tenga, Engebretsen, & Bahr, 2004) collected videotapes and injury information for regular league matches during the Norwegian season of 2000 (April through October). In 174 matches, 425 incidents were recorded: 1.2 incidents per team per match or 75.5 incidents per 1000 playing hours. A total of 121 acute injuries were reported from the same matches, i.e. 0.3 injuries per team per match or 21.5 injuries per 1000 playing hours. In an analysis of the incidence and characteristics of injuries sustained during the 2010 FIFA (Fédération Internationale de Football Association) World Cup, Dvorak and colleagues (Dvorak, Junge, Derman, & Schwellnus, 2011) identified 229 injuries, of which 82 match-play and 58 training injuries were expected to result in time-loss, giving an incidence of 40.1 matchplay and 4.4 training injuries per 1000 h. Contact with another player was the most frequent cause of matchplay (65%) and training (40%) injuries. The data showed that the most frequent diagnoses were thigh strain and ankle sprain (Dvorak et al., 2011). The incidence of match injuries during the 2010 FIFA World Cup was lower than in the three previous World Cups (Dvorak et al., 2011). This might have been the result of more attention to injury prevention, less foul play, and stricter refereeing (Dvorak et al., 2011). Dvorak and colleagues (2011) showed that training injuries differed substantially from matchplay injuries with respect to diagnosis and cause, but not severity. While it could be expected that training injuries were more often a result of overuse and noncontact trauma than match injuries, 12 training injuries were reported to be caused by foul play. Six of these injuries were reported from one team (Dvorak et al., 2011). The incidence of time-loss training injuries was similar to those at the European Championships (1.3–3.9 per 1000 training h) (Ekstrand et al., 2011; Hagglund et al., 2006). Injury risk can also be affected by the match schedule. Indeed, Dupont et al. (2011) showed that the injury rate can be much higher when two matches are played in the same week, compared with a oncea-week schedule. In the 2006 World Cup in Germany, Dvorak et al. (2007) reported an injury rate of 81 injuries per 1000 h of exposure, which is slightly lower than that of Dupont et al. (2011) with 97.7 injuries per 1000 h. In this tournament, the high rates of injury may have been linked to the limited number of recovery days between two matches (given that most matches were played every 3–5 days) and the repetition of matches in a congested fixture schedule. Although some of the players studied probably had more than 4 days of recovery between matches, this study highlights the higher risk of injuries when the recovery between two matches is short. In this context, Ekstrand and colleagues (Ekstrand, Walden, & Hagglund, 2004) reported that a congested soccer calendar increases the risk of injury or underperformance. Results from that study confirm the high risk of injury during a congested calendar. In contrast, Carling and colleagues (Carling, Le Gall, & Dupont, 2012) observed no difference in the injury rate of a congested fixture period and that outside such a period. Rahnama and colleagues (Rahnama, Reilly, & Lees, 2002) assessed the exposure of English Premier League players to injury risk during the 1999–2000 season by rating the injury potential of playing actions during competition with respect to type of playing action, period of the game, zone of the pitch, and playing either at home or away. The results suggested that some playing actions were associated with higher injury risk than others. Indeed, receiving a tackle, receiving a ‘charge’, and making a tackle were seen to be associated with a substantial injury risk, while goal punching, kicking the ball, shot on goal, set kick, and heading the ball were all categorized as exposure to a significant injury risk. Injury risk was highest in the first and last 15 min of a game, reflecting the intense engagements in the opening period and the possible effect of fatigue in the closing period. Injury risk was also concentrated in the areas of the pitch where possession of the ball is most vigorously contested, i.e. the attacking and defending zones close to the goal. Injury potential was no greater in away matches than in home games (Rahnama et al., 2002). Hawkins et al. (2001) reported the highest injury rates in the 15-min period at the end of each half, with significantly more injuries in the second half of matches. This may be the result of fatigue of the muscles and other body organs as well as depleted muscle glycogen stores (Reilly, 1997) and players becoming hypo-hydrated (Saltin, 1973). The relationship between fatigue and injury is hard to quantify, but there is evidence to suggest that fatigue is associated with injury. Empirical observations has shown that fatigued individuals are vulnerable to injury (for a review, see Schlabach, 1994). Fatigue may not be the sole cause of injury, but rather a contributing factor. After reviewing the literature regarding the aetiology of injury strains, Worrell and Perrin (1992) reported that fatigue was one of several factors that may contribute to the frequency of hamstring strains. Because muscle glycogen depletion is associated with fatigue and injury, it should also be treated as a possible risk factor. Muscle glycogen stores are almost entirely derived from carbohydrate. Both indirect and direct evidence support the notion that depleted muscle glycogen stores contribute to injury. Indirectly, it is quite clear that depleted muscle glycogen stores coincide with fatigue, and fatigue in turn is associated with injury, as mentioned above. Although most evidence is related to relationships rather than cause-and-effect, many researchers Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 Soccer injury rates during Ramadan strongly do suggest a cause-and-effect relationship between low muscle glycogen stores and injury risks (for a review, see Schlabach, 1994). Depletion of up to 84–90% of intramuscular glycogen stores has been observed in soccer players at the end of a soccer match (Jacobs, Westlin, Karlsson, Rasmusson, & Houghton, 1982). Soccer players with low glycogen stores at the start of a match had almost no glycogen left in their working muscle and the physical performance of these players decreased in the second half compared with those players with higher pre-game and half-time glycogen muscle stores (Jacobs et al., 1982). Because there is a limited capacity to store muscle glycogen, and because muscle glycogen is the predominant fuel in exercise of moderate to severe intensity, the nutritional focus should be on carbohydrate consumption (for a review, see Schlabach, 1994). The absolute amount of carbohydrate in the diet may be an important factor for the recovery of muscle and liver glycogen stores after training and competition (Ivy, 2001). In this context, it is important to note that an inadequate nutrient intake and hypohydration could affect the physical health of the athlete and possibly contribute to sports injuries (Convertino et al., 1996). Large sweat losses, insufficient fluid intake, and consequent fluid deficits will likely impair performance and may increase the risk of hyperthermia and heat injury (Bergeron et al., 2005), stressing the importance of appropriate hydration before training and matches in soccer players. In this context, by ending the day dehydrated, fasting players could be exposed to a higher risk of injury. Another factor associated with fatigue-related injuries is sleep duration. Research indicates a relationship between sleep deprivation and decreased performance in adults (Belenky et al., 2003; Taylor, Rogers, & Driver, 1997). Recently, Luke et al. (2011) demonstrated that fatigue-related injuries among athletes aged 6–18 years were related to sleeping less than 6 h the night before the injury (P ¼ 0.028). In contrast, the same authors reported no difference in the average number of hours of sleep or reported sleep-deprivation between the overuse and acute injury groups of their study. However, since fatigue is implicated in increased injury risk, planning for adequate sleep before and during training and competition is important when determining a player’s training schedule and setting up an event schedule, especially if travel is involved. As sleeping schedule is radically changed during Ramadan, this month could be a cause of higher injury risks for athletes. Studies that describe injury risk and injury patterns in soccer are typically conducted over seasons of European or American Leagues (Andersen et al., 2004; Dupont et al., 2011; Ekstrand et al., 2011). To our knowledge, no study has focused on the injury rates of Muslim soccer teams during the regular part of 3 the season or during the holy month of Ramadan. During this period, fasting Muslims refrain from eating, drinking, smoking, and having sexual activities daily from dawn to sunset for 30 consecutive days. Since the Islamic calendar is based on the lunar cycle, which advances 11 days compared with the seasonal year, Ramadan occurs at different times of the seasonal year over a 33-year cycle (Chaouachi, Leiper, Souissi, Coutts, & Chamari, 2009c), and in different environmental conditions between years in the same country (Leiper, Molla, & Molla, 2003; Leiper et al., 2008). Ramadan fasting is intermittent in nature, and there is no restriction to the amount of food or fluid that can be consumed after dusk and before dawn. It is supposed that most Muslim soccer players fast during Ramadan. Therefore, since the sporting calendar is not adapted for religious observances, and Muslim soccer players continue to compete and train during the month of Ramadan, various studies have examined whether this religious fast has any effect on athletic performance (for reviews, see Chaouachi et al., 2009c, 2012) and cognitive functions (Maughan, Fallah, & Coyle, 2010; Waterhouse, 2010). It has been suggested that few aspects of physical fitness are negatively affected, and only modest decrements are observed (Chaouachi et al., 2009c). The evidence to date indicates that high-level athletes can maintain performance during Ramadan if physical training, diet, and sleep are well controlled. Nevertheless, despite this, fasting athletes report higher fatigue at the end of Ramadan (Chaouachi et al., 2009c; Güvenç, 2011). The increased perception of fatigue reported during Ramadan fasting and the combination of intense training with altered carbohydrate intake, hydration status, and sleeping disturbances may place fasting Muslim athletes at greater risk of overreaching or overtraining during Ramadan (Chaouachi et al., 2009a, 2009b), which can result in physical injury, especially overuse injuries (Johnson & Thiese, 1992). Most previous studies have addressed whether the holy month of Ramadan has any detrimental impact on performance and cognitive functions. To our knowledge, no study has examined the effect of this religious fast on injury rates in athletes. Therefore, we present some data from a pilot study that investigated the injury rate during Ramadan in a professional soccer squad over two consecutive competitive seasons by comparing the injury rates between fasting and non-fasting players within the same team. Methods Participants Training loads, Hooper’s index (Hooper & Mackinnon, 1995), and injuries were monitored in 42 professional soccer players (age 24 + 4 years; height Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 4 K. Chamari et al. 185 + 8 cm; body mass 78 + 4 kg) over two consecutive seasons. This group included players who were in the team for only a few months, i.e. those who were transferred in or out of the team. A high rate of player turnover explains the relatively high number of players who were monitored in the present study. All members of the squad were monitored during the study period, i.e. one month before Ramadan, the month of Ramadan, and the month after Ramadan during each of the two seasons. Goalkeepers were included in the study. The studied team was competing at the highest level in the Tunisian first league and also participated in the African Cup of teams (CAF Cup) during the second season of the study. Fasting status was determined only at the end of the Ramadan month via a personal interview with each player and discrete cross-checking with the player’s team-mates and whenever possible with family members and/or friends. Based on this information, the players were retrospectively organized into fasting and non-fasting groups. The fasting group consisted of all players who fasted throughout the Ramadan month and the non-fasting group consisted of players who opted not to fast throughout the Ramadan month for both training and match days. All Muslim players who fasted in this study had practised the fast during Ramadan for at least the previous 7 years. The players were not aware of the study objectives. All players provided written informed consent and the study’s procedures were approved by the Clinical Research Ethics Committee of the National Centre of Medicine and Science in Sports (Tunis, Tunisia). weeks after Ramadan in each year. During Ramadan, training sessions and matches were performed after dusk (starting at 22.00 h), while before and after Ramadan the sessions and matches were scheduled in the afternoon (starting at 15.00 or 16.00 h) and sometimes in the morning for training (for the days in which two training sessions were scheduled, starting at 09.30 h). Ambient temperature, atmospheric pressure, and relative humidity were measured for each training session (Figure 1). Injury rate Injury data were considered when a player was unable to take full part in future soccer training sessions or matches owing to physical complaints (Fuller et al., 2006). Information about the circumstances (training or match injury) and mechanism of injury (traumatic or overuse injury) were recorded. The same team doctor diagnosed all injuries, and an injured player was considered injured until the team doctor cleared him to participate in full training or matches. The durations of training sessions (in the gym and on the field of play) and matches for each player were precisely recorded. Study design The study focused on the month of Ramadan for two consecutive seasons (i.e. from 10 August to 11 September 2010 and from 1 to 30 August 2011) where the daily fast occurred from * 04.00 h to * 19.15 h, for a total duration of * 15 h and 15 min. During the study, both fasting and non-fasting players underwent an identical training programme under the supervision of the coaching staff and the principal investigator of the study. Goalkeepers (n ¼ 4 or 5, depending on the period of the season) had their own training programme that was not monitored by ratings of perceived exertion (RPE) and Hooper’s index. Training data were collected during the 12 weeks of pre-season and the start of the competitive season, from July to October in each of the 2 years, thus including the month of Ramadan in both seasons. During these periods, the team participated in local league and continental games based on a classical one-game-a-week schedule. All field players were monitored for 4 weeks before Ramadan, the month of Ramadan (4 weeks), and 4 Figure 1. (A) Ambient temperature (8C), (B) atmospheric pressure (mmHg), and (C) relative humidity (%) before, during, and after Ramadan. ¤ , 2010; &, 2011. Soccer injury rates during Ramadan Injury rates (training, match, overall) were calculated as injuries per 1000 h of exposure. Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 Monitoring of training loads Daily individual training load was calculated using Foster’s session-RPE procedure (Foster et al., 2001). This method involves multiplying the training duration in minutes by the mean training intensity. The session-RPE scale is based on the Borg category ratio (CR-10) RPE scale as modified by Foster et al. (2001), which translates the player’s perception of effort into a numerical score between 0 and 10. This method has further been validated in soccer by Impellizzeri and colleagues (Impellizzeri, Rampinini, Coutts, Sassi, & Marcora, 2004). The player is asked to respond to a simple question – How was your workout? – with the aim of obtaining an uncomplicated response that reflects the athlete’s global impression of the workout. All players had been familiarized with this scale for at least one month before the start of the study and followed standardized instructions for session-RPE. Each player’s sessionRPE was collected approximately 20–30 min after each soccer training session and match to ensure that the perceived exertion referred to the whole training session and match rather than the most recent (end-ofsession) exercise intensity (Impellizzeri et al., 2004). Monitoring overtraining Overtraining syndrome was monitored by Hooper’s Index (Hooper & Mackinnon, 1995). This method is based on self-analysis questionnaires involving wellbeing ratings relative to fatigue, stress, delayed-onset muscle soreness (especially ‘‘heavy’’ legs), and sleep quality/disorders (Hooper & Mackinnon, 1995). Before each training session and match, the players were asked to rate subjective quality of sleep, and quantity of stress, delayed-onset muscle soreness, and fatigue on a scale of 1–7 in accordance with Hooper and Mackinnon (1995). Hooper’s Index is the sum of the four subjective ratings. Statistical analysis Data are expressed as means and standard deviations (s). Two-way analysis of variance (ANOVA) was 5 used to compare differences between periods (before Ramadan, during Ramadan, and after Ramadan) in weekly training load, strain, duration, and environmental conditions (temperature, humidity, and atmospheric pressure). Multivariate analysis of variance (MANOVA) was used to compare differences between groups (fasting and non-fasting) and periods (before Ramadan, during Ramadan, and after Ramadan) in Hooper’s Index, sleep, stress, delayedonset muscle soreness, and fatigue. Significant differences in injury rates between periods were assumed if the 95% confidence intervals (CI) did not overlap. Significant differences in injury rates between fasting and non-fasting players were assumed if the 95% confidence intervals (CI) did not overlap. Statistical significance was set at P 5 0.05. Results Two-way ANOVA showed no significant differences between the three periods (before Ramadan, during Ramadan, after Ramadan: F ¼ 1.05, P 4 0.05) in weekly training load, strain, duration, and environmental conditions (temperature, humidity, and atmospheric pressure) (Table I). The MANOVA showed a significant difference between fasting and non-fasting groups (F ¼ 4.79, P 5 0.01) in Hooper’s Index and stress. No significant differences were observed between the three periods (P 4 0.05) for Hooper’s Index, sleep, stress, delayed-onset muscle soreness, and fatigue for both groups. No significant interaction was observed between periods and groups (P 4 0.05). Independent samples t-test showed that, compared with nonfasting players, fasting players had significantly lower (P 5 0.05; Table II) Hooper’s Index and stress during and after Ramadan. When asked about the timing of their sleep, players of both groups reported not going to bed before 03.00 h due to late training sessions and family, and socio-cultural and/or religious events during the whole month of Ramadan. Overall injury rate and corresponding rates in the whole squad are presented in Table III. Significantly higher rates of non-contact injuries and overuse injuries during training were observed in fasting players during Ramadan, compared with before and after the holy month (Table IV). No significant Table I. Comparisons of weekly training load, strain, and duration (mean of the two seasons monitored and standard deviations) Weekly training load (AU) Weekly training strain (AU) Weekly training duration (min) Before Ramadan* Ramadan* After Ramadan* 2045 (314) 2492 (634) 487 (73) 1757 (558) 2525 (1826) 419 (130) 1807 (440) 1839 (586) 422 (109) *Each period consisted of 4 weeks in each year. AU ¼ arbitrary units. 6 K. Chamari et al. Table II. Comparison of Hooper Index (sleep, stress, delayed-onset muscle soreness, and fatigue) (mean of the two seasons monitored and standard deviations) Before Ramadan* Fasting Hooper’s Index Sleep Stress Delayed-onset muscle soreness Fatigue 9.8 2.3 2.0 2.6 Ramadan* Non-fasting (2.0) (0.6) (0.3) (0.6) 11.6 2.5 3.0 2.9 2.9 (0.6) (3.7) (0.8) (1.5) (0.8) Fasting 10.5 2.6 2.1 2.9 3.2 (0.7) After Ramadan* Non-fasting (1.1)a (0.2) (0.3)a (0.4) 12.1 2.7 3.1 3.2 3.1 (0.5) (1.2) (0.3) (1.0) (0.3) 3.4 (0.3) Fasting 10.0 2.4 1.9 2.7 Non-fasting (0.6)a (0.4) (0.2)a (0.3) 3.0 (0.4) 11.3 2.5 2.8 2.9 (1.6) (0.5) (1.1) (0.2) 3.2 (0.3) Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 *Each period consisted of 4 weeks in each year. a Significantly different from non-fasting players (P 5 0.05). Table III. Overall numbers of injuries and corresponding rate for the whole squad in the two seasons 2010 season 2011 season Mean of two seasons Number of injuries Injury rate (injuries per 1000 h exposure) Number of injuries Injury rate (injuries per 1000 h exposure) Injury rate (injuries per 1000 h exposure) 7 12 4 7.6 13.8 4.3 2 7 5 2.3 10.9 9.1 4.9 12.3 6.7 Before Ramadan Ramadan After Ramadan Table IV. Comparisons of injury rates in fasters and non-fasters for the two seasons monitored Before Ramadan* Fasting Injury rate Rate of contact injury Rate of non-contact injury Rate of contact injury during matches Rate of overuse injury during matches Rate of contact injury during training Rate of overuse injury during training 3.3 2.7 0.6 1.6 (0–6.8) (0–6.3) (0–3.3) (0–4.1) Non-fasting 1.7 1.1 0.6 1.1 (0–5.2) (0–4.7) (0–3.3) (0–3.5) Ramadan* Fasting 8.1 1.3 6.8a 0.7 (4.5–11.6) (0–4.9) (4.0–9.5) (0–3.2) After Ramadan* Non-fasting 3.9 0.7 3.2 0.7 (0.3–7.4) (0–4.3) (0.4–5.9) (0–3.2) Fasting 4.5 3.4 1.1 2.1 (0.9–8.1) (0–7.0) (0–3.9) (0–4.5) Non-fasting 1.6 1.6 0 0 (0–5.1) (0–5.1) (0–2.8) (0–2.4) 0 (0–1.3) 0 (0–1.3) 1.2 (0–2.4) 0 (0–1.3) 0.5 (0–1.8) 0 (0–1.3) 1.1 (0–3.1) 0 (0–2.0) 0.6 (0–2.6) 0 (0–2.0) 1.3 (0–3.3) 1.6 (0–3.5) 0.6 (0–2.2) 0.6 (0–2.2) 5.6a (4.0–7.2) 3.2 (1.5–4.8) 0.5 (0–2.2) 0 (0–1.6) *Each period consisted of 4 weeks in each year. a Significantly higher than before and after Ramadan (P 5 0.05). Note: Values in bracket are 95% confidence intervals. differences were found between fasting and nonfasting players in total injury rates. The overall number of injuries for the two seasons combined was 9, 19, and 9 injuries for before, during, and after Ramadan, respectively. This gives a mean of 4.5 injuries for each of the two 4-week periods either side of Ramadan, and a mean of 9.5 injuries during the month of Ramadan. For each season, the overall number of fasting and non-fasting players who were injured was 12 and 5 for 2010, and 6 and 5 for 2011, respectively. Of these players, only one goalkeeper got injured in a traumatic training injury (ankle sprain). For comparison purposes, the injuries of the team over a period of 88 weeks, from 1 June 2010 to 19 February 2012 (*22 months, including both months of Ramadan), resulted in a total of 121 injuries with monthly rates as displayed in Table V. Total injuries over the two study periods (before, during, and after Soccer injury rates during Ramadan 7 Table V. Monthly injury rate (for each 4-week period) for the studied team over 88 weeks (*22 months) Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 Number of injuries per 4-week periods (n) Volume of training and matches (h) Number of players in the squad (n) Total monthly training and match exposure (h) Injury rate (injury per 1000 h exposure) Mean s Min. Max. 5.5 29.2 28.7 844.1 6.9 2.7 5.0 1.7 179.1 3.7 0.0 20.0 26.0 520.4 0.0 10.0 39.9 32.0 1276.8 17.3 Ramadan) showed that 5 of 9 injuries before Ramadan, and 4 of 9 injuries after Ramadan, were sustained during matches, whereas only 4 of 19 were sustained during matches during Ramadan. Moreover, overuse injuries were lower during the months just before and after Ramadan with only 2 of 9 injuries in both cases, while this type of injury dramatically increased during Ramadan with 16 overuse injuries out of a total of 19 injuries observed for the two months of Ramadan monitored. For these two Ramadan months, the 16 non-contact injuries were distributed as follows: 7 muscle spasms (contractures), 7 tendinosis, and 2 muscle strains (one tear at the hamstrings and one strain at the thigh-adductors). The 7 contractures were located at the hamstrings (n ¼ 3), foot flexors (n ¼ 2), thigh-adductors (n ¼ 1), and knee extensors (n ¼ 1). The 7 tendinosis injuries were located at the thigh-adductors (n ¼ 3) and foot flexors (n ¼ 1), with the remaining 3 located at the abdomen and pelvis. Discussion The aim of this study was to examine the effects of the month of Ramadan and its specific socio-cultural and religious environment on the injury rates of professional elite soccer players over two consecutive seasons. The main findings of this study were the absence of any significant difference between fasting and non-fasting players with respect to general injury rates, while the non-contact and training overuse injury rates were significantly higher during than both before and after Ramadan for fasting players. Nevertheless, these groups showed differences for Hooper’s Index and perceived stress, with fasting players having lower Hooper’s Index and stress during and after Ramadan than non-fasting players. Moreover, no difference was observed between fasting and nonfasting players for the reported quality of sleep, and quantity of delayed-onset muscle soreness and fatigue before, during, and after Ramadan. Training load, training strain, and duration were not significantly different between the three periods or between groups for the two monitored seasons. Some recent work has suggested that elite athletes could avoid marked decrements in their physical capacities while undergoing the intermittent fast of Ramadan, when they were maintaining their usual training loads; rather, most measured fitness variables were maintained at their pre-Ramadan values (for a review, see Chaouachi et al., 2009c). Consequently, the technical staffs of the soccer team in the present study chose not to decrease training load during Ramadan for the two seasons studied. Although not objectively measured, the team’s fitness remained at a relatively high level of competitiveness and the team kept qualifying for the African Cup of teams (CAF Cup). Even if not involved in a congested match fixture, and the fact that the general injury rate was not altered, the non-contact and the training overuse injuries were significantly increased in fasting players during Ramadan. The injury rates of the present study (Tables III and V) were consistent with data reported for the Union of European Football Associations (UEFA) (Ekstrand et al., 2011), English Premier League (Hawkins et al., 2001), Swedish Premier League (Hagglund et al., 2006), Scottish league (Dupont et al., 2011), and Norwegian league (Andersen et al., 2004). Ekstrand et al. (2011) reported a rate of 8.0 injuries per 1000 h for 23 first team squads selected by UEFA as belonging to the 50 best European teams for seven consecutive seasons (i.e. 2001 to 2008). The results of the present study are also consistent with the data of Hawkins et al. (2001), who reported an average of 1.3 injuries per player per season in the English Premier League. In the Swedish Premier League, Hägglund et al. (2006) prospectively recorded individual exposure and time-loss injuries over two full consecutive seasons (2001 and 2002). They showed that training and match injury incidences were similar between seasons (5.1 vs. 5.3 injuries per 1000 training hours and 25.9 vs. 22.7 injuries per 1000 match hours). In elite Scottish soccer, Dupont et al. (2011) reported similar injury rates for one-game-a-week with an overall injury rate of 4.1 injuries per 1000 h of exposure, which was composed of 2.5 injuries per 1000 h of training and 19.3 injuries per 1000 h of match-play. In a prospective study in Norway, Andersen et al. (2004) collected videotapes and injury information for the regular league matches of the Norwegian season (April Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 8 K. Chamari et al. through October 2000). During 174 matches, 425 incidents were recorded, that is, 1.2 incidents per team per match or 75.5 incidents per 1000 playing hours. A total of 121 acute injuries were reported from the same matches, that is, 0.3 injuries per team per match or 21.5 injuries per 1000 playing hours. In this regard, the injury rate of the present study outside the month of Ramadan is lower than that generally reported in the literature. It should be stressed that this injury rate relates to pre-season and the start of the season, which might explain these lower rates. Preseason is characterized by a high prevalence of endurance training and fitness training, which were performed in the present study in a progressive manner. The low frequency of matches at these stages might be the cause of the low overall injury rates of the studied periods. In this context, it has been well demonstrated that match injury rates are always much higher than training injury rates. Moreover, Koutedakis and Sharp (1998) showed that the preparation phase of the season is accompanied by fewer injuries than the competition phase. Despite a higher mean overall injury rate during the month of Ramadan in the two studied seasons (i.e. 12.3 injuries per 1000 h exposure vs. 4.9 for before Ramadan and 6.7 for after Ramadan), the differences were not significant. Nevertheless, the rate of overuse and non-contact injuries during training found in the present study was significantly higher during than both before and after Ramadan in fasting players (Table IV). As this increase in injury rate was observed in fasting players, the Ramadan fasting-induced hypohydration hypothesis might explain this result (Huffman, Yard, Fields, Collins, & Comstock, 2008; for a review on hydration, see Maughan & Shirreffs, 2012). As hydration status was not monitored, it remains possible that both groups’ players were relatively hypohydrated during Ramadan fasting especially during daylight hours. Even if the reported quality of overall sleep was not altered during Ramadan, the sleeping scheduling was greatly modified with players not going to bed before 03.00 h. Recently, Luke et al. (2011) showed that sleeping less than 6 h the night before an injury occurred was associated with an increase in fatiguerelated injuries (P ¼ 0.028). The results of the present study show no influence of Ramadan on the perceived sleep quality of the participants. As Hooper’s Index is a simple general index that assesses sleep quality, the absence of change does not necessarily mean that sleep architecture was not altered. Even if the participants were generally satisfied about their whole 24-h sleep quality, it may be that the time spent in the different sleeping phases was modified. In this context, it has been well established that sleeping architecture is characterized by different phases at the beginning and the end of the night (Czeisler, Weitzman, Moore-Ede, Zimmerman, & Knauer, 1980; Duffy, Kronauer, & Czeisler, 1996). The change in sleeping and nutritional habits during Ramadan (i.e. much less nightsleep and more afternoon naps for fasters and nonfasters and major changes in eating patterns for the fasting players) may have altered the players’ physiological status during Ramadan, probably leading to the observed higher overuse injury rate during the fasting month (Bogdan, Bouchareb, & Touitou, 2001; Montelpare, Plyley, & Shephard, 1992; Reilly & Waterhouse, 2007). (For a review of sleep disturbances effects, see Roky, Herrera, and Ahmed, 2012.) After sleep architecture disturbances, another possible cause of higher overuse injuries could also be the end of Ramadan state of the fasting players. Chaouachi et al. (2009b) have clearly shown that elite athletes continuing to complete high training loads during Ramadan often endure higher levels of fatigue and are likely to experience a cascade of small biochemical adjustments, including hormonal, immunoglobulin, and antioxidant system changes, and an elevated inflammatory response. These variations are close to what is observed in tissue traumatic processes as found in athletes in an over-reaching or overtraining state (Chaouachi et al., 2009b). Although the variations are small and may not be considered clinically relevant, they may still signal physiological stress (Chaouachi et al., 2009b). In this context, the overtraining syndrome has been referred to as staleness or chronic fatigue with mental weariness along with some associated injuries that are observed in parallel with a significant decline in physical performance (Halson & Jeukendrup, 2004; Kentta & Hassmen, 1998). Overtraining affects the musculoskeletal system in that serum creatine kinase levels are increased and enzymatic markers of muscle tissue injury significantly elevated the day after high training loads. It is unclear whether the observed overuse injuries observed in the overtrained or overreached athlete could be the result of excessively high training loads and/or the impaired ability to recover from training. At odds with many studies (for a review see Chaouachi et al., 2009c) showing that Ramadan induces additional stress on the athlete, the stress assessed by the Hooper Index during Ramadan in the present study was not different from stress measured before and after Ramadan for non-fasting players. Nevertheless, the fasting players reported decreased stress for Ramadan and for the month after Ramadan. It could be speculated that the religious beliefs and the well-being of living and practising a holy month could have led to a lower perception of stress in the fasting players. The possible habituation process in the fasting players has also to be considered, as they reported that they had fasted and trained simultaneously for 7 years and thus the absence of total injury Soccer injury rates during Ramadan risk with respect to non-fasting players relates to habituated fasters. Newly fasting players’ data are not available from the present study. Downloaded by [Hong Kong Institute of Vocational], [del wong] at 02:15 15 June 2012 Conclusion Several changes that occur during Ramadan fasting may potentially affect the injury risk for fasting players. In Muslim majority countries, non-fasting players may also be affected by changes in eating and sleeping habits and in the scheduling of training and match-play. Preliminary data, however, show the absence of an effect of the holy month of Ramadan on the general injury rates of fasting and non-fasting elite soccer players where weekly training loads were maintained during Ramadan. 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