**2. Muscle injuries in soccer during traditional conditions**

The first part of this chapter is dedicated to present muscle injury rates during matches and training sessions out of the month of Ramadan in English (Hawkins et al., 2001), Swedish

© 2013 Chamari et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

(Hagglund et al., 2006), Norwegian (Andersen et al., 2004) league Championships, European Championships (Ekstrand et al., 2011) and World Cups (Dvorak et al., 2011) in order to be able to further compare them with those found during the holy month of Ramadan.

competitive season, traumatic (or contact) injuries and hamstring strains were the more frequent observed sport accidents, while during the pre-season, overuse injuries/muscle injuries were more frequently reported injuries (35.27% of all injuries during the seven years studied, Table 2). Recurrent injuries accounted for 12% of all injuries recorded during the seven successive studied seasons, causing longer absences than non-recurrent injuries (24 vs. 18 days, respectively, p <0.0001). In the same context, Hawkins et al., (2001) have shown that recurrent injuries represented 7% of 6030 injuries reported with 91 clubs in English Professional Football

**Fracture** 160 (4) 7 9 59 (4) 85 (12) **Other bone injury** 26 5 1 6 14 (2) **Disloaction/subluxation** 50 (1) 5 4 24 (1) 17 (2) **Sprain/ligament injury** 828 (18) 123 (13) 197 (34) 334 (20) 174 (25)

**Muscle injury/Strain** 1581 (35) 212 (22) 397 (34) 765 (46) 207 (30) **Tendon injury** 327 (7) 95 (10) 71 (6) 101 (6) 60 (9) **Haematoma/contusion** 744 (17) 306 (32) 282 (24) 141 (9) 15 (2) **Abrasion** 7 3 3 1 0 **Laceration** 31 10 (1) 11 10 0 **Contusion** 34 5 14 (1) 14 1 **Nerve injury** 29 7 3 14 5 **Synovitis/effusion** 158 (4) 55 (6) 36 (3) 55 (3) 12 (2) **Overuse complaints** 285 (6) 110 (11) 99 (9) 59 (4) 17 (2) **Other type** 91 (2) 23 (2) 27 (2) 24 (1) 17 (2) **Total injuries 4483 971 1164 1651 697**

Values within brackets show percentage of total injuries (lower line - values below 1% not shown)

(including the groin) was the site of 87% of the total injuries reported (Table 3).

**Table 2.** Injury pattern by severity of injuries from 2001 to 2008 (rate: injuries/1000 h of exposure) with the best

The rate of injuries during trainings and matches-play in the study reported Ekstrand et al., (2011) are consistent with the data of Hawkins et al., (2001), who reported A total of 6030 injuries collected over two seasons (i.e., from July 1997 through to the end of May 1999) with an average of 1.3 injuries per player per season of professional football in England. Table 3 shows the nature of the injuries sustained during training and matches reported by Hawkins et al., (2001). Muscles injuries represented 46% of all the injuries. The rate of muscle injuries in trainings was high than during matches-play (p<0.001). In Table 3, Injuries classified as "other" report back and nerve related pathologies/injuries, vertebral column-disc derangements, and non-specific pain, no individual category amounting to more than 0.5% of all injuries. It is of interest to note that the players' dominant side showed a greater sustained number of injuries compared with the non-dominant side (50% vs. 37%, respectively, p<0.01), and the lower limbs

**Total 1-3 Days 4-7 Days ays "/> 28 Days**

3 7 41 (2) 73 (10)

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307

during two consecutive seasons.

**Mensiscus/catilage** 124 (Rejeski

European clubs adapted from Ekstrand et al., (2011)

et al.)

*Injury type*

Recently, Ekstrand et al., (2011) conducted a prospective cohort study in European Professional Soccer Players from 2001 to 2008. The study focused on seven consecutive seasons (July-May). In 2000, 14 teams from top European clubs (clubs participating at the highest level in Europe in the last decade) were selected by UEFA and invited to participate in the study of Ekstrand et al., (2011). Eleven teams agreed to participate and provided complete data for the 2001/2002 season. In the following seasons, 12 other teams were selected by UEFA and included in the study. Ekstrand et al., (2011) presented the results of the teams that have met the criteria for inclusion and comprehensive data sent over the full seasons. Table 1 shows these character‐ istics.


**Table 1.** Characteristics of teams, players and exposure from 2001 to 2008 belonging from the best European clubs adapted from Ekstrand et al., (2011).

The authors reported 4483 injuries corresponding to 566 000 h of exposure (i.e, 475 000h of training and 91 000h of match-play) over the seven seasons, inducing a rate of 8.0 injuries / 1000 h. Muscle injuries were the highest type of injuries observed with 1581 injuries during the 566 000 h of exposure. A player performed an average of 34 games and had 162 training sessions each season (median values of 35 and 173, respectively). The overall average exposure during the football season was of 254 h, with 213 hours of training and 41 hours of games (median values being 269, 222 and 40, respectively). The rate of injuries during matches was higher than that of training (27.5 vs. 4.1, respectively, p <0.001). The rates of muscle injuries and others types of injuries during training and the match remained steady during the 8-years with no significant difference in-between seasons.

A player may undergo on average two injuries per season, thus a team of typically 25 players can expect about 50 injuries each season. Table 2 shows the different types of injuries according to their severity with the top European clubs in according to Ekstrand et al., (2011). During the competitive season, traumatic (or contact) injuries and hamstring strains were the more frequent observed sport accidents, while during the pre-season, overuse injuries/muscle injuries were more frequently reported injuries (35.27% of all injuries during the seven years studied, Table 2). Recurrent injuries accounted for 12% of all injuries recorded during the seven successive studied seasons, causing longer absences than non-recurrent injuries (24 vs. 18 days, respectively, p <0.0001). In the same context, Hawkins et al., (2001) have shown that recurrent injuries represented 7% of 6030 injuries reported with 91 clubs in English Professional Football during two consecutive seasons.

(Hagglund et al., 2006), Norwegian (Andersen et al., 2004) league Championships, European Championships (Ekstrand et al., 2011) and World Cups (Dvorak et al., 2011) in order to be able

Recently, Ekstrand et al., (2011) conducted a prospective cohort study in European Professional Soccer Players from 2001 to 2008. The study focused on seven consecutive seasons (July-May). In 2000, 14 teams from top European clubs (clubs participating at the highest level in Europe in the last decade) were selected by UEFA and invited to participate in the study of Ekstrand et al., (2011). Eleven teams agreed to participate and provided complete data for the 2001/2002 season. In the following seasons, 12 other teams were selected by UEFA and included in the study. Ekstrand et al., (2011) presented the results of the teams that have met the criteria for inclusion and comprehensive data sent over the full seasons. Table 1 shows these character‐

**Age** 25.7 (4.4) 25.7 (4.4) 25.8 (4.0) 26.0 (4.3) 25.8 (4.1) 25.9 (4.5) 25.6 (4.6) 25.5 (4.6)

**Table 1.** Characteristics of teams, players and exposure from 2001 to 2008 belonging from the best European clubs

The authors reported 4483 injuries corresponding to 566 000 h of exposure (i.e, 475 000h of training and 91 000h of match-play) over the seven seasons, inducing a rate of 8.0 injuries / 1000 h. Muscle injuries were the highest type of injuries observed with 1581 injuries during the 566 000 h of exposure. A player performed an average of 34 games and had 162 training sessions each season (median values of 35 and 173, respectively). The overall average exposure during the football season was of 254 h, with 213 hours of training and 41 hours of games (median values being 269, 222 and 40, respectively). The rate of injuries during matches was higher than that of training (27.5 vs. 4.1, respectively, p <0.001). The rates of muscle injuries and others types of injuries during training and the match remained steady during the 8-years

A player may undergo on average two injuries per season, thus a team of typically 25 players can expect about 50 injuries each season. Table 2 shows the different types of injuries according to their severity with the top European clubs in according to Ekstrand et al., (2011). During the

**2001/2002 2002/2003 2003/2004 2004/2005 2005/2006 2006/2007 2007/2008**

213 (71) 219 (66) 243 (64) 203 (67) 229 (65) 207 (75) 207 (75) 206 (68)

254 (85) 262 (80) 290 (74) 243 (80) 273 (79) 247 (89) 245 (90) 246 (83)

41 (23) 43 (22) 47 (23) 40 (24) 44 (24) 40 (23) 38 (24) 40 (24)

34 (17) 36 (16) 39 (16) 33 (17) 35 (16) 33 (17) 32 (17) 33 (17)

162 (53) 174 (53) 181 (45) 151 (47) 171 (46) 156 (55) 155 (56) 160 (52)

to further compare them with those found during the holy month of Ramadan.

istics.

**Training hours/ players**

306 Muscle Injuries in Sport Medicine

**Exposure hours/ player**

**Match hours/ player**

**No of matches/ player**

**No of matches/ player**

Values are mean (SD)

adapted from Ekstrand et al., (2011).

**All seven seasons**

**Seasons**

with no significant difference in-between seasons.


Values within brackets show percentage of total injuries (lower line - values below 1% not shown)

**Table 2.** Injury pattern by severity of injuries from 2001 to 2008 (rate: injuries/1000 h of exposure) with the best European clubs adapted from Ekstrand et al., (2011)

The rate of injuries during trainings and matches-play in the study reported Ekstrand et al., (2011) are consistent with the data of Hawkins et al., (2001), who reported A total of 6030 injuries collected over two seasons (i.e., from July 1997 through to the end of May 1999) with an average of 1.3 injuries per player per season of professional football in England. Table 3 shows the nature of the injuries sustained during training and matches reported by Hawkins et al., (2001). Muscles injuries represented 46% of all the injuries. The rate of muscle injuries in trainings was high than during matches-play (p<0.001). In Table 3, Injuries classified as "other" report back and nerve related pathologies/injuries, vertebral column-disc derangements, and non-specific pain, no individual category amounting to more than 0.5% of all injuries. It is of interest to note that the players' dominant side showed a greater sustained number of injuries compared with the non-dominant side (50% vs. 37%, respectively, p<0.01), and the lower limbs (including the groin) was the site of 87% of the total injuries reported (Table 3).

In the Swedish Premier League, Hagglünd et al., (2006) prospectively recorded individual exposure and loss of time due to injury over two full consecutive seasons (2001 and 2002). They showed that the rate of injuries and training match between the seasons were similar (5.1 vs. 5.3 injuries/1000 h of training and 25.9 vs. 22.7 injuries/1000 h of match-play; respectively) but the analysis of injury severity and injury patterns showed variations between seasons. In Norway, Andersen et al., (2004) collected data and videotapes of injuries prospectively during regular league matches in 2000 (April to October). Over 174 matches, 425 injuries were recorded: 1.2 injuries per team per match or 75.5 injuries per 1000 hours played. A total of 121 acute injuries were reported from game, giving a rate of 0.3 injuries per match and team or 21.5 injuries per 1000 hours played. In an analysis of the rates and characteristics of injuries in the edition of the 2010 FIFA World Cup, Dvorak et al., (2011) reported 229 injuries, of which 140 injuries requiring rest. The remaining injuries did not prevent the players to take part to the consecutive training sessions. In this study, 32 finalist squads participated (including 736 players). 82 injuries during matches and 58 injuries during training requiring rest were observed, resulting in a rate of 40.1 injuries/1000-h during matches (95% CI 31.4 to 48.8) and 4.4 injuries/1000-h during training (95% CI 3.3 to 5.5). Table 4 shows the Location and diagnosis of match and training injuries during this study.

**All injuries Competition injuries Training injuries**

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Muscle Injuries in Professional Soccer Players During the Month of Ramadan

**No % No % No %**

*Muscular strain/rupture 2225 37 1322 35 859† 42* Ligamentous sprain/rupture 1153 19 765 20 370 18 *Muscular contusion 431 7 343 9 79† 4* Tissue bruising 336 6 263 7 64† 3 Fracture 253 4 186 5 61† 3 Other 238 4 123 3 95† 5 Tendinitus 237 4 107 3 10† 5 Inflammatory synovitis 192 3 114 3 73 4 Mensiscal tear 148 2 80 2 63‡ 3 Hernia 120 2 56 1 40 2 *Overuse 108 2 44 1 44† 2* Dislocation 81 1 50 1 28 1 Periostitis 75 1 52 1 23 1 Cut 73 1 60 2 13† 1 Chondral lesion 69 1 41 1 24 1 Capsular tear 54 1 47 1 6† 0 Paratendinitis 46 1 17 0 27† 1 Bursitis 29 1 10 0 18† 1 Blister 6 0 2 0 4 0 Skin abrasion 3 3 2 0 1 0 Not classified 153 101 96 3 44 2 Total\* 6030 3780 98 2046 99

Thigh 1388 23 889 24 468 22 Knee 1014 17 610 17 355 16 Ankle 1011 17 682 19 304† 14 Lower leg 753 12 452 12 272 13 Groin 596 10 226 6 340† 16 Neck/spine 352 6 176 5 159† 7 Foot 302 5 202 6 94 4 Upper limb 153 3 99 3 50 2 Hip 135 2 82 2 46 2 Abdomen 90 1 50 1 36 2 Chest 86 1 77 2 7† 0 Head 67 1 55 2 11† 1 Toe 63 1 50 1 12† 1 Other 15 0 12 0 1 0 Not specified 5 0 4 0 1 0 Total\* 6030 99 3666 100 2160 100

**Table 3.** Nature and location of injuries sustained during match-play and training with 91 professional soccer clubs in

\* Percentage totals may subject to rounding errors associated with individual components

† p<0.01 Different proportions between training and competition ‡ p<0.05 Different proportions between training and competition

England during two consecutive seasons adapted from Hawkins et al., (2001).

*Nature of injury*

*Location of injury*

Contact with another player caused by foul-play based on the judgment of the team physician was the most common cause of injuries during matches (65%) and training sessions (40%). These data showed that the most common diagnoses were contusions at the thigh and ankle sprain (Dvorak et al., 2011). In the same context, Ekstrand et al., (2011) showed that 21% (n = 538) of all injuries recorded during matches of seven successive seasons with the best profes‐ sional players were due to foul-play according to the referee, with the majority being due to foul play by an opponent (n=520). The most common foul-play injuries were ankle sprains (15%), knee sprains (9%) and thigh contusions (10%). In the two studied seasons, (2006/07 and 2007/08), the match timing of injury showed that foul-play injuries were evenly distributed among the two halves (74 vs. 84 for first and second half, respectively, p=0.47). In this context, receiving a tackle, receiving a ''charge'', and making a tackle were categorized as 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 exposing to a significant injury risk. With respect to match minute, Injury risk was highest in the first and last 15 minutes of the games. This probably reflects the intense engagements in the opening period of each game, during which the players are highly motivated and the effects of fatigue not yet clearly observable, and the possible effect of fatigue in the closing period. The injury risk was also concentrated in the areas of challenge where possession of the ball is the most hotly contested, i.e., the attack and defense areas near the goals. The injury rate during the 2010 FIFA World Cup was lower than in the previous three World Cups (Dvorak et al., 2011) as presented in Table 2. This may be a result of a connection to additional injury prevention, and a reduced fool play probably due to the more stringent arbitration (Dvorak et al., 2011). Dvorak et al., (2011) showed that training injuries differed substantially from match injuries with respect to diagnosis (Table 4) and cause, but not in severity. It was reported that training injuries were more often as a result of overuse and non-contact trauma than match injuries. In this context, it is interesting to note that 12 out of 104 training injuries were reported to be contact-injuries caused by foul-play. Out of these 12 injuries, 6 were reported from one team. In this case the rate of time-loss training injuries was similar to those reported for the European Championships {i.e., 1.3–3.9 per 1000 hours of exposure to Training} (Hagglund et al., 2006; Ekstrand et al., 2011).

#### Muscle Injuries in Professional Soccer Players During the Month of Ramadan http://dx.doi.org/10.5772/56292 309


\* Percentage totals may subject to rounding errors associated with individual components

† p<0.01 Different proportions between training and competition

In the Swedish Premier League, Hagglünd et al., (2006) prospectively recorded individual exposure and loss of time due to injury over two full consecutive seasons (2001 and 2002). They showed that the rate of injuries and training match between the seasons were similar (5.1 vs. 5.3 injuries/1000 h of training and 25.9 vs. 22.7 injuries/1000 h of match-play; respectively) but the analysis of injury severity and injury patterns showed variations between seasons. In Norway, Andersen et al., (2004) collected data and videotapes of injuries prospectively during regular league matches in 2000 (April to October). Over 174 matches, 425 injuries were recorded: 1.2 injuries per team per match or 75.5 injuries per 1000 hours played. A total of 121 acute injuries were reported from game, giving a rate of 0.3 injuries per match and team or 21.5 injuries per 1000 hours played. In an analysis of the rates and characteristics of injuries in the edition of the 2010 FIFA World Cup, Dvorak et al., (2011) reported 229 injuries, of which 140 injuries requiring rest. The remaining injuries did not prevent the players to take part to the consecutive training sessions. In this study, 32 finalist squads participated (including 736 players). 82 injuries during matches and 58 injuries during training requiring rest were observed, resulting in a rate of 40.1 injuries/1000-h during matches (95% CI 31.4 to 48.8) and 4.4 injuries/1000-h during training (95% CI 3.3 to 5.5). Table 4 shows the Location and diagnosis

Contact with another player caused by foul-play based on the judgment of the team physician was the most common cause of injuries during matches (65%) and training sessions (40%). These data showed that the most common diagnoses were contusions at the thigh and ankle sprain (Dvorak et al., 2011). In the same context, Ekstrand et al., (2011) showed that 21% (n = 538) of all injuries recorded during matches of seven successive seasons with the best profes‐ sional players were due to foul-play according to the referee, with the majority being due to foul play by an opponent (n=520). The most common foul-play injuries were ankle sprains (15%), knee sprains (9%) and thigh contusions (10%). In the two studied seasons, (2006/07 and 2007/08), the match timing of injury showed that foul-play injuries were evenly distributed among the two halves (74 vs. 84 for first and second half, respectively, p=0.47). In this context, receiving a tackle, receiving a ''charge'', and making a tackle were categorized as 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 exposing to a significant injury risk. With respect to match minute, Injury risk was highest in the first and last 15 minutes of the games. This probably reflects the intense engagements in the opening period of each game, during which the players are highly motivated and the effects of fatigue not yet clearly observable, and the possible effect of fatigue in the closing period. The injury risk was also concentrated in the areas of challenge where possession of the ball is the most hotly contested, i.e., the attack and defense areas near the goals. The injury rate during the 2010 FIFA World Cup was lower than in the previous three World Cups (Dvorak et al., 2011) as presented in Table 2. This may be a result of a connection to additional injury prevention, and a reduced fool play probably due to the more stringent arbitration (Dvorak et al., 2011). Dvorak et al., (2011) showed that training injuries differed substantially from match injuries with respect to diagnosis (Table 4) and cause, but not in severity. It was reported that training injuries were more often as a result of overuse and non-contact trauma than match injuries. In this context, it is interesting to note that 12 out of 104 training injuries were reported to be contact-injuries caused by foul-play. Out of these 12 injuries, 6 were reported from one team. In this case the rate of time-loss training injuries was similar to those reported for the European Championships {i.e., 1.3–3.9 per 1000 hours of

of match and training injuries during this study.

308 Muscle Injuries in Sport Medicine

exposure to Training} (Hagglund et al., 2006; Ekstrand et al., 2011).

‡ p<0.05 Different proportions between training and competition

**Table 3.** Nature and location of injuries sustained during match-play and training with 91 professional soccer clubs in England during two consecutive seasons adapted from Hawkins et al., (2001).


**Years 1998 2002 2006 2010**

**Table 5.** Average number of injuries per match in FIFA World Cups 1998–2010 (grey: all injuries; black: time-loss

(Reilly, 1997) and players becoming hypo-hydrated (Saltin, 1973).

Muscle injury risk can also be affected by the match schedule. Indeed, Dupont et al., (2011) showed that the muscle injury rate can be much higher when 2 matches are played during the week, compared to classical one-game per week schedule. The highest muscle injury was located at thigh (32 vs 15 injuries, respectively. These results confirmed that insufficient recovery between matches leads to fatigue and increases the risk of muscle injury. In the 2006 World-Cup (Germany), Dvorak et al., (2007) reported an injury rate slightly lower than the results of Dupont et al., (2011). In this tournament, the high rate of injuries may have been linked to the limited number of recovering days between 2 matches (given that most matches were played every 3 to 5 days) and the repetition of matches in a congested fixture schedule. Although some of the players studied probably had more than 4-days recovery between matches, this result highlights the higher risk of muscle injuries when the recovery between 2 matches is short. In this context, Ekstrand et al., (2004) reported that a congested soccer calendar increased the risk of muscle injury or underperformance. Results from these afore‐ mentioned studies confirm the high risk of injury during a congested calendar. Nevertheless, conflicting results come from Carling et al., (2012) who did not observe any difference in the injury rate between congested fixture period and outside such a period. In the same context, recently with a higher number of matches, Dellal et al., (Accepted 2012) showed that muscle injuries during the congested periods of fixture (3 different congested fixture periods, 6 matches in 21 days during each one of the congested periods) was not different to those reported in matches outside these periods (55.8% of total injuries from 14.4 injuries/1000h during congested period vs 55.6% from 15.6 injuries/1000h during non-congested period). Rahnama et al., (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 the type of playing action, period of the game, zone of the pitch, and playing either at home or away games. Muscle injury rate was no different in away matches than at home games (Rahnama et al., 2002). From the 3836 injuries for which the timing of injury was known, Hawkins et al., (2001) found that a greater than the average frequency of injuries was observed during the final 15 minutes of the first half and the final 30 minutes of the second (p<0.01). Table 6 shows the distribution of the competitive match injuries with respect to timing of occurrence. Despite the increase in injury rate observed towards the later stages of the first half (i.e. the last 15 min of play, which was similar with the same trend for the second half), overall, there remained a greater number of injuries recorded in the second half compared to the first (57% *v* 43%, respectively, p<0.01). This may be the result of fatigue of the muscles and other body organs as well as muscle glycogen stores near to depletion

all injuries 2.4 2.7 2.3 2 time-loss injuries 0 1.7 1.5 1.3

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Injuries per match

injuries) adapted from Dvorak et al., (2011).

\* Information was missing for at least one injury.

**Table 4.** Location and diagnosis of match and training muscle injuries (n=229) in 2001 in the Norway professional soccer season adapted from Dvorak et al., (2011).


**Table 5.** Average number of injuries per match in FIFA World Cups 1998–2010 (grey: all injuries; black: time-loss injuries) adapted from Dvorak et al., (2011).

**Location and diagnostics Match injuries Training injuries**

**Table 4.** Location and diagnosis of match and training muscle injuries (n=229) in 2001 in the Norway professional

\* Information was missing for at least one injury.

310 Muscle Injuries in Sport Medicine

soccer season adapted from Dvorak et al., (2011).

**All With absence All With absence**

Muscle injury risk can also be affected by the match schedule. Indeed, Dupont et al., (2011) showed that the muscle injury rate can be much higher when 2 matches are played during the week, compared to classical one-game per week schedule. The highest muscle injury was located at thigh (32 vs 15 injuries, respectively. These results confirmed that insufficient recovery between matches leads to fatigue and increases the risk of muscle injury. In the 2006 World-Cup (Germany), Dvorak et al., (2007) reported an injury rate slightly lower than the results of Dupont et al., (2011). In this tournament, the high rate of injuries may have been linked to the limited number of recovering days between 2 matches (given that most matches were played every 3 to 5 days) and the repetition of matches in a congested fixture schedule. Although some of the players studied probably had more than 4-days recovery between matches, this result highlights the higher risk of muscle injuries when the recovery between 2 matches is short. In this context, Ekstrand et al., (2004) reported that a congested soccer calendar increased the risk of muscle injury or underperformance. Results from these afore‐ mentioned studies confirm the high risk of injury during a congested calendar. Nevertheless, conflicting results come from Carling et al., (2012) who did not observe any difference in the injury rate between congested fixture period and outside such a period. In the same context, recently with a higher number of matches, Dellal et al., (Accepted 2012) showed that muscle injuries during the congested periods of fixture (3 different congested fixture periods, 6 matches in 21 days during each one of the congested periods) was not different to those reported in matches outside these periods (55.8% of total injuries from 14.4 injuries/1000h during congested period vs 55.6% from 15.6 injuries/1000h during non-congested period). Rahnama et al., (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 the type of playing action, period of the game, zone of the pitch, and playing either at home or away games. Muscle injury rate was no different in away matches than at home games (Rahnama et al., 2002). From the 3836 injuries for which the timing of injury was known, Hawkins et al., (2001) found that a greater than the average frequency of injuries was observed during the final 15 minutes of the first half and the final 30 minutes of the second (p<0.01). Table 6 shows the distribution of the competitive match injuries with respect to timing of occurrence. Despite the increase in injury rate observed towards the later stages of the first half (i.e. the last 15 min of play, which was similar with the same trend for the second half), overall, there remained a greater number of injuries recorded in the second half compared to the first (57% *v* 43%, respectively, p<0.01). This may be the result of fatigue of the muscles and other body organs as well as muscle glycogen stores near to depletion (Reilly, 1997) and players becoming hypo-hydrated (Saltin, 1973).


hydration could affect the physical performance of the athlete and possibly contribute to sports injuries (Convertino et al., 1996). Large sweat losses, insufficient fluid intake, and consequent fluid deficits could likely impair performance and may increase the risk of hyperthermia and related problems (Bergeron et al., 2005), stressing the importance of appropriate hydration before training and matches in soccer players. In this context, as ending the day dehydrated, fasting players (as observed during Ramadan) could be exposed to higher risks of muscle

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Another important cause related with fatigue-associated injuries is the sleeping duration and/ or quality. Research indicates a relationship between sleep deprivation and decreased performance in adults (Taylor et al., 1997; Belenky et al., 2003). Recently, Luke et al., (2011) confirmed that fatigue-related injuries were related to sleeping less than 6 hours the night before the injury (p = 0.028) among athletes aged 6 to 18 years. In contrast, Luke et al., (2011) have reported no difference in the average amount of sleeping hours or reported sleepdeprivation between the overuse and acute injury groups of their study. However, with evidence of the obvious contributing role of fatigue in increasing muscle injury risk, planning for adequate sleep before and during training or competition events should be another notable consideration in determining a player's training schedule and setting-up an event schedule, especially if travel is involved. As sleeping schedule is acutely changed during Ramadan, this

Investigations describing muscle injury risk and muscle injury patterns in soccer are usually conducted over seasons of European or American Leagues (Andersen et al., 2004; Ekstrand et al., 2011; Dupont et al., 2011). To our knowledge, only one study (Chamari et al., 2012) has focused on the injury-rates of muslim soccer players during the holy month of Ramadan. In this context, to our knowledge this is the only scientific publication having studied the effect

During the wholly month of Ramadan, fasting Muslims do not eat, drink, smoke, or have sexual activities daily from dawn to sunset. 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 et al., 2009a). This implies that Ramadan occurs at different environmental conditions between years in the same country (Leiper et al., 2003; Leiper et al., 2008). It is supposed that most Muslim soccer players fast during Ramadan, even if some exceptions are observed. 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. Therefore, since the international sporting calendar is not adapted for religious observances, and Muslim soccer players continue to compete and train during Ramadan, various studies have determined whether this religious fast has any effect on athletic

month could be a cause of higher muscle injury risks for athletes.

**3. Muscle injuries in soccer during Ramadan period**

of Ramadan fasting on sports' injuries.

**3.1. Ramadan characteristics**

injury.

**Table 6.** Timing of occurrence of injuries in matches with 91 English professional soccer clubs during two consecutive sessions adapted from Hawkins et al., (2001).

There is evidence to suggest that fatigue is associated with muscle injury. Indeed, empirical observations have shown that fatigued individuals are susceptible to muscle injury [See for review (Schlabach, 1994)]. Fatigue may not be the only cause of muscle injury, but rather a contributing factor. After reviewing the literature regarding the etiology of muscle injuries, Worrell and Perrin (1992) reported that fatigue was one of several factors that may contribute to frequency of hamstring strains (one of the common muscle injuries in soccer).

Since muscle glycogen depletion is associated with fatigue and possibly injury, it should also be treated as a potential risk factor. Muscle glycogen stores are almost entirely derived from carbohydrate intake. Both indirect and direct evidence support the notion that depleted muscle glycogen stores contribute to muscle injury. Indirectly, it is quite clear that depleted muscle glycogen stores coincide with fatigue, and fatigue in turn is associated with muscle injury as mentioned above. Although most of the evidence involves relationships rather than showing cause, many of the investigations strongly suggest a cause-and-effect relationship between low muscle glycogen stores and injury risks [See for review (Schlabach, 1994)]. Depletion up to 84-90% of intramuscular glycogen stores has been observed in soccer players at the end of a soccer match (Jacobs et al., 1982). Soccer players with low glycogen stores at the start of a match had almost no glycogen left in their working muscle and physical performance of these players decreased in the second half in comparison to those players with higher pre-game and halftime glycogen muscle levels (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 [See for review (Schlabach, 1994)]. The absolute amount of carbohydrates 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 mention that an inadequate nutrient intake and hypohydration could affect the physical performance of the athlete and possibly contribute to sports injuries (Convertino et al., 1996). Large sweat losses, insufficient fluid intake, and consequent fluid deficits could likely impair performance and may increase the risk of hyperthermia and related problems (Bergeron et al., 2005), stressing the importance of appropriate hydration before training and matches in soccer players. In this context, as ending the day dehydrated, fasting players (as observed during Ramadan) could be exposed to higher risks of muscle injury.

Another important cause related with fatigue-associated injuries is the sleeping duration and/ or quality. Research indicates a relationship between sleep deprivation and decreased performance in adults (Taylor et al., 1997; Belenky et al., 2003). Recently, Luke et al., (2011) confirmed that fatigue-related injuries were related to sleeping less than 6 hours the night before the injury (p = 0.028) among athletes aged 6 to 18 years. In contrast, Luke et al., (2011) have reported no difference in the average amount of sleeping hours or reported sleepdeprivation between the overuse and acute injury groups of their study. However, with evidence of the obvious contributing role of fatigue in increasing muscle injury risk, planning for adequate sleep before and during training or competition events should be another notable consideration in determining a player's training schedule and setting-up an event schedule, especially if travel is involved. As sleeping schedule is acutely changed during Ramadan, this month could be a cause of higher muscle injury risks for athletes.
