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INTRODUCTION

Volleyball is among the most popular sports in the world, with more than 200 member countries in the Federation Internationale de Volley-Ball (FIVB) and about 150 million players (Bahr and Bahr, 1997). Although injury is a potential outcome of participation, volleyball is a non contact game, where players from the opposing teams are separated by the net, so it may be expected that the incidence of injuries is low. However, studies have indicated that injuries in volleyball are quite frequent (Solgard, Nielsen, Moller-Madsen, Jacobsen, Yde, & Jensen, 1995; Ferretti, De Carli, & Fontana, 1998; Schultz, 1999; Verhagen Van der Beek, Bouter, Bahr, Van Mechelen, 2004). The injury incidence is between 1,7 and 4,2 per 1000 hours of play (Aagaard & Jorgensen, 1996; Bahr & Bahr, 1997; Solgard et al., 1995) and it is the fourth most common source of sports injuries (Solgard et al., 1995).

Comparing volleyball with other team sports, studies have shown that the injury rate in volleyball is lower than in other team sports such as soccer and basketball. Presumably this difference can be attributed to the non contact nature of the game, as players from opposing teams are separated. Nevertheless, the most common mechanism of injury in volleyball is considered to be a forced supination that occurs when the blocking player’s foot lands on an opposing spiker’s foot that has come underneath the net and is in the “conflict zone”. When this happens, the result is an inversion injury to the lateral collateral ligament complex of the blocker’s ankle. This fact construes with the result of many studies that the most frequent acute injury type in volleyball is ankle sprain (Gangitano R, Puvirenti, Ardito 1981; Hell & Schonle, 1985; Gerberich, Luhman, Finke, Priest, & Beard, 1987; Yde & Nielsen, 1988; Schafle, Requa, Patton, & Garrick, 1990).

Concerning the age related injury occurrence, it has been shown that in soccer, the injury incidence in youth players (16 to 18 years of age) is similar to the incidence of senior players (more than 18 years) (Maffulli, King, & Helms, 1994; Kirialanis, Malliou, Beneka, Gourgoulis, Giofstidou, & Godolias, 2002) assuming that the contact nature of the sport causes many ankle sprains and knee injuries. The possibility that the injury occurrence in volleyball -as a non contact sport- is age-related still remains a question. There is still a gap concerning the injury occurrence in male athletes in relation to the injury type, severity, anatomical location of injuries, if they occurred during practice or game or if they were recurrent or not.

This study aimed to record the injury rate in all age categories of Greek male volleyball players and clarify the role of age in injury occurrence. Moreover, information related to injuries such as occurrence during training or game, time of season, severity, anatomical location and diagnosis, number of recurrent injuries, playing position and factors related to the injury occurrence was recorded.

MATERIALS AND METHODS

Study population
A total of 407 Greek male volleyball players participating in all Volleyball Championships in Greece according to the Greek Volleyball Federation (Senior’s championship for athletes more than 18 years old, Junior’s championship for athletes from 15 to 18 years old and Youth’s championship for athletes from 12 to 14 years old) were observed on a weekly basis for the 2005-06 period. This was almost 30% of the volleyball players participating in the National Championship in A1 and A2 categories. Table 1 gives the age-groups and anthropometric characteristics of the involved participants and Table 2 the specialty of players in terms of age group.

Table 1. Age and anthropometric characteristics of the Volleyball players.

Characteristic	Youth 12-14 years old (n=72)	Junior 15-18 years old (n=109)	Senior more than 18 years old (n=268)
Age (years)	13.3 (1.2)	16.1 (0.98)	26.7 (4.5)
Weight (kg)	60.1 (6.7)	75.2 (10.2)	86.4 (8.5)
Height (cm)	170.1 (5.6)	183.1 (6.4)	190.8 (7)

Values are means (SD).

Table 2. The playing position in terms of age group of the participants

Specialty of players	Youth (n=72)	Junior (n=109)	Senior (n=226)	Total
Setter	9 (12.5%)	21 (19.3%)	40 (17.7%)	70
Libero	12 (16.7%)	8 (7.3%)	27 (11.9%)	47
Outside Hitter	25 (34.7%)	31 (28.4%)	46 (20.4%)	102
Universal	9 (12.5%)	28 (25.7%)	56 (24.8%)	93
Middle Hitter	17 (23.6%)	21 (19.3%)	57 (25.2%)	95
Total	72 (100%)	109(100%)	226 (100%)	407

Data collection and definition of the injury
An orthopaedic surgeon, a physiotherapist, and a trainer made up the questions that were included in the interview. The injury incidence rate, the characteristics of the injuries (severity, diagnosis) and the anatomical location of the muscle skeletal injuries, which occurred during the practice and competition in all the championship period, were recorded prospectively for the last year. Injury was defined as "any mishap occurring during scheduled games or practices that cause an athlete to miss a subsequent game or practice session". Injuries were classified into three grades of severity: minor (absence from training or competition for less than one week); moderate (absence from training or competition for one week to one month); major (absence from training or competition for more than one month). This classification has been used in many studies (Kirialanis et al, 2002; Kirialanis, Malliou, Beneka, & Giannakopoulos, 2003; De Loes M., 1990; Ekstrand & Tropp, 1990)

RESULTS

Data were statistically analysed using X² analysis of SPSS statistical package to determine whether any of the previously mentioned factors had a relation to the incidence of injury. In all cases, the null hypothesis was rejected when p <0.05.


Injury rate
During the period of the study (12 months) the total sample (n=407) reported 248 injuries. It is notable that, according to records, 189 players (46,4% of the total players) were injured: 156 (82,5%) players were injured once, 28 (14,8%) players were injured twice, and 5 (2,6%) players three times (missing 21 cases).

In order to study the different injury rate in relation to age, the 407 male players were divided into three age-related groups (age categories according to the Greek Volleyball Federation’s championships). Of the 189 injured players, 18 players aged 12-14 years (youth) (9,5%), 40 players aged 15-18 (junior) (21,2%) and 131 aged more than 18 (senior) (69,3%). The injury rate in senior players was statistically different in comparison to the injury rate to the other age groups (X² = 29,534, p=0,001<05).

The 407 male volleyball players reported 248 injuries during a total exposure time of 110596 h per year, representing an overall incidence of 0.60 injuries per player per year. In terms of volleyball participation over 12 months they reported 2.4 injuries per 1000 hours of training and games per player.

72 volleyball youth players (aged 12-14 years) reported 22 injuries during a total exposure time of 11520 h per year, representing overall incidence of 0.30 injuries per player per year. In terms of volleyball participation over 12 months they reported 1.9 injuries per 1000 hours (training and game) per player.

109 junior volleyball players (aged 15-18 years) reported 41 injuries during a total exposure time of 22236 h per year, representing an overall incidence of 0.37 injuries per player per year. In terms of volleyball participation over 12 months they reported 1.8 injuries per 1000 hours (training and games) per player.

Finally, the 226 volleyball senior players (aged >18 years) reported 185 injuries during a total exposure time of 69156 h per year, representing overall incidence 0.81 injuries per player per year. In terms of volleyball participation over 12 months the 226 players reported 2.8 injuries per 1000 hours (training and games) per player.

Training or game and Time of season
The injury rate during training sessions was statistically different in comparison to game injury rate (X² = 331, p<.05) but there were no differences in relation to the age groups (Table 3).


Table 3. The injury rate for the volleyball players in terms of different age group and training or game

	No cases (%)	Injuries (cases)	Injuries in training (cases)	Injuries in games (cases)
Athletes (n=407)	407 (100%)	248	168*	80
Youth	72 (17.6%)	22	15	7
Junior	109 (26.7%)	41	31	10
Senior	226 (55.6%)	185	130	55

*Statistical significance

Subdividing the year into three periods (preseason period that lasted 2.5 months, competitive season period that lasted 6 months and postseason period that lasted 3 months) allowed assessing the role that each period might have to injury occurrence. The injury rate for the volleyball players (all age groups) into these three periods of year was 19.2% (42 cases) for the preseason, 79.8% ( 174 cases) for the competitive season and .9% (2 cases) for the post season. The injury rate in competitive season was statistically different in comparison to preseason and postseason injury rate for the total volleyball players (X² = 632, p=.000 <.05). Table 4 shows the injury rate and the period of annual cycle that the players were injured in each age group.

Table 4. Injury occurrence in terms of the season of the year and different age groups

	Preseason injuries	Competitive Season injuries	Post season injuries	Missing cases
Injuries (n=248)	42 (19.3%)	174 (79.8%)*	2 (0.9%)	30
Youth	6	14	-	1
Junior	8	30	1	3
Senior	28	130	1	26

*Significantly different than the other periods(X² = 750,6, p<.05). 

Type, anatomic location and diagnosis of injury.
191 (86.4%) were acute injuries and 30 (13.5%) overuse syndromes (27 missing cases). Table 5 shows that, for the total sample, injuries were distributed throughout the body. The most common anatomic location of injury for the athletes was ankle (86 cases, 38.9%), followed by knee (54 cases, 24.4%), lower back (31 cases, 14%), shoulder (28 cases, 12.7%) and hand (22 cases, 10%). According to the results the acute injuries were significant different in comparison to overuse syndromes (X²= 117.9 p<0.01) and the ankle was the most common injured anatomical location (X ² =62.73 p<0.01).
According to physician diagnosis, 221 cases were analyzed and the most common injury was the ankle sprain (118 cases, 53.4%), followed by muscle strain (40 cases, 18.1 %), fracture (33 cases, 14.9%), back pain (19 cases, 8.6%), tendonitis (11 cases, 5%). According to X² analysis the ankle sprain was significantly different in comparison to the other injuries (X²=165.7 p<0.01)

Table 5. Acute and chronic injuries in terms of anatomical location

Location	Acute injuries* (n=191)	Overuse syndromes (n=30)	Total injuries (n=221)
Ankle-foot*	86*	-	86 (38.9)*
Knee-thigh	42	12	54 (24.4%)
Spine	24	7	31 (14%)
Shoulder	19	9	28 (12.7%)
Hand	20	2	22 (10%)
Missing values			27

*Significantly different  

Severity of injury
The severity of injuries was shown in terms of absence from competition or training after the injury. The rate of mild injuries was 24 % (53 cases), that of moderate injuries was 58.4 % (129 cases), and that of major injuries was 15.4 % (34 cases) (significant difference between them, X²= 162,85 p<0.01). No statistical differences between severities of injury in relation to age (p=0.450) was observed. The major injuries of the participants showed that only the 6.3 % (12 cases) of them influenced adversely their volleyball career.

Recurrent injuries
The recurrent injury episodes in 189 cases were analyzed. According to the statistical analysis X² the recurrent episodes (42 cases) were statistically less compared with the cases with no recurrent episodes (147 cases) (X² = 58,32, p<.05). In addition there was no difference found when comparing the recurrent episodes between age group, (X² = 0,553, p=.743 >0.05). In addition, almost all of the players followed a rehabilitation program.

Playing position of the injured volleyball player- Injury factor
Outside hitters and middle hitters presented more injuries than the other players (X² = 24,724, p<0.05) (Table 6). In addition “incorrect sprawls”, “Step on others’ foot” and “fatigue” were the most common injury factors (Table 7).

Table 6. The position of the injured volley ball players

Position	Cases 221 (%)
Setter	35 (15,8%)
Libero	24 (10,9%)
Middle hitter	50 (22,6%)
Outside hitter	68 (31%)*
Universal	44 (19,9%)
Missing values	0

*Significantly different than in other locations

Table 7. Injury factor for volley ball players

Injury factor	221 Cases (%)
Incorrect sprawls	51 (23,3%)
Wrong technique	24 (10,8%)
Step on others’ foot	55 (24,7%)
Ball contact	20 (8,9%)
Fatigue	52 (23,7%)
Inappropriate warm up	12 (5,4%)
Other	5 (2,4%)
Missing values	2

DISCUSSION

The results of the present study revealed that 46.4% of the volleyball players sustained one or more injuries during the season. The prevalence of the injuries (0.60 injuries/player/season) is almost the same with that recently reported by Augustsson et al, (Augustsson, Augustsson, Thomee, & Svantesson, 2006) who noted a rate of injuries corresponding to 0.68 for elite male Swedish division, but lower than that previously reported by Aagaard and Jorgensen (1996) who noted a rate of injuries corresponding to 1.5 injuries/player/season. However, the differences in study design might partly explain the difference in study results.

When the results have been dissected in relation to age, the prevalence of injuries (0.30 injuries/player/year) for 12-14 year old players and for 15-18 year old players (0.37 injuries/player/year) was significantly lower than that of older players (more than 18 years old, 0.81 injuries/player/year). In order to clarify this issue, the authors of the present study examined the injury occurrence rate in relation to the total exposure time of the athletes (total amount of training hours and game play) for each age category. The results revealed important differences in injury occurrence rate between the different age categories (1.9/1000h/player for 12-14 years, 1.8/1000h/player for 15-18 years and 2.8/1000h/player for more than 18 years of age), meaning that when the total exposure time has been taken into account, even more significant differences were found in injury rates between the three age categories. In conclusion, the authors suggest that any findings in injury occurrence rate must be interpreted in relation to the total exposure time in order to have more realistic conclusions.

Gisslen et al (Gisslèn, Gyulai, Söderman, & Alfredson, 2005) agree with the results of the present study that injury occurrence is age related and junior volleyball players have a lower injury rate than the senior ones. Several studies have reported an increase in the number of overuse injuries because of an increase in the number of training hours. Aagaard and Jorgensen (1996) reported that the number of training hours had increased by more than 50% during a 10 year period and Ferretti et al (Ferretti, Puddu, Mariani, & Neri, 1984) found that jumper’s knee was more common in volleyball players who play more than four times a week.

Moreover Cook et al. found structural changes in 71/268 patellar tendons (26%) in a similar group of junior basketball players (Cook, Khan, Kiss, & Griffiths, 2000) while Fredberg and Bolvig (2002) have reported structural tendon changes in 18/98 patellar tendons (18%) in an asymptomatic group of senior elite soccer players.

Drexler et al (Drexler, Briner, & Reeser J. (2001) stated that there does appear to be an association between higher level of play and increased frequency of injury. Higher skill levels subject athletes to greater injury risk. Elite athletes train for more hours, so the cumulative stress on their bodies may make them more vulnerable to injury. Similarly, Gisslen et al (2005) noticed that almost all the painful tendons belonged to individuals in the second and third grades, where there is more and heavier weight training and more match specific training compared to the first grade.

Bahr and Bahr (1997) also examined the injury incidence in relation to total exposure time and found an overall injury incidence at 1.7/1000h/player for men volleyball athletes, which is less than that of the present study. However, the authors included only older athletes (mean age 21,7 years) reporting only acute injuries in their estimate, and not younger athletes and overuse injuries.

Moreover when calculating exposure time in retrospective studies one common problem that is usually associated with the results is the subjective information that could lead to an over or under-estimated report. The problem is that exposure time for game play is rarely calculated individually, even in prospective studies the actual amount of time during which each player is at risk of injury is difficult to investigate. The true exposure time can therefore be higher or lower than that reported, which complicates the comparison with other studies.

The comparison of our results with others reported by similar studies is also very difficult because none of them examined the differences in injury occurrence in relation to age categories. Aagaard and Jorgensen (1996) noted a rate of injuries corresponding to 1.5 injuries/player/year for Danish men, however no data have been referenced which correlated the influence of age in injury occurrence. The injury incidence rate in relation to different age categories has been examined by Kirialanis et al (2002) in artistic gymnastics athletes and they found no differences.

Age was not an important factor influencing injury incidence related to the severity of injury or the season that it occurred. The majority of injuries were of moderate severity, fewer were of mild severity and very few were of major severity. This result is not in accordance with that of Augustsson et al (2006) and of Aagaard et al (1996) who found that the majority of injuries were of minor severity but they included not only men but also women in their studies. This result could be also explained by the fact that the participants in this study were not only elite athletes, but any athlete participating in the Greek National Championship Volleyball.

Ankle injuries accounted for almost half of all acute injuries recorded in the present study, and previous studies have also shown that ankle sprains account for one quarter to one-half of all acute injuries in volleyball (Gangitano et al., 1981; Hell & Schonle, 1985; Gerberich, et al., 1987; Yde & Nielsen, 1988; Schafle, et al., 1990; Bhairo, Nijsten, Van Dalen, & ten Duis, 1992; Bahr, Lian, Karlsen, & Øvredo 1994; Solgard, Nielsen, Moller-Madsen, Jacobsen, Yde, & Jensen, 1995). In the present study almost 18% of the injured athletes were injured twice or three times during the season, while almost 22% of the injuries were recurrent episodes. Similarly (Bahr et al., 1994) found that in 78% of the cases, the players had a history of at least one previous ankle injury during their career. It is important to note that recurrent episodes in the present study have been defined as injuries that occurred with the same diagnosis and in the same site.

Another important finding of the present study was the factors related to injury occurrence. “Step on other’s foot” and “incorrect sprawls” were the two more significant injury factors. These two factors are usually associated with blocking, followed by spiking, which are the most frequent skills in volleyball that require jumping and are associated with high incidence of ankle injuries (Schafle et al 1990; Watkins & Green, 1992; Briner & Benjamin, 1999). A 1987 review of outpatient rehabilitation records of 106 patients treated for volleyball injuries found that 63% of the injuries were related to jumping (Goodwin-Gerberich, Luhmann, Finke, Priest, & Beard, 1987). The most common mechanism of ankle injury in volleyball is when a player’s foot intrudes into the opponent’s side of the court as long the foot remains in contact with the line that runs directly beneath the net. When this happens, the usual result is an inversion injury to the lateral collateral ligament complex of the blocker’s ankle (Briner & Benjamin, 1999).

Concerning the playing position the present study revealed that the majority of injuries occurred in outside hitters, middle hitters and universals. All of them are responsible for blocking, hitting and generally are staying for more playing time in the court (Selinger, 1987). The results of the present study are in agreement with many authors reporting that defense is associated with a smaller number of injuries, and serving, passing and setting with even fewer. (Goodwin-Gerberich, et al., 1987; Schafle et al 1990; Watkins & Green, 1992; Briner & Benjamin, 1999).

Comparing the injuries between acute and chronic in the present study, just 14% were chronic injuries and the rest were acute, while the literature indicates that volleyball players are usually vulnerable to chronic injuries (Lian, Refsnes, Engebretsen, & Bahr, 2003). This is not surprising, since many overuse injuries do not keep the players from participating in training or games. For example it is stated that most players with jumper’s knee, the most common overuse injury in volleyball, still manage to take part in training or games (Lian, Holen, Engebretsen, & Bahr, 1996). This is a very serious problem associated with epidemiological research on sports injuries which is related to the definition of injury (Ekstrand & Karlsson, 2003). The criterion of ‘time lost’ which has been previously recommended, was used in this study (Keller, Noyes, & Buncher, 1987). The disadvantage of this definition is that one player may elect to continue playing volleyball, while another player would stop playing with a similar injury. The report from one player may therefore result in the recording of an injury, while another will not. This problem might be quite common in volleyball as well as in other sports, as overuse injuries often do not keep the players from participating in training of matches. However, the ‘time lost’ definition represents a useful measure in the severity of injury and takes account of those injuries that most probably have an important impact on the player’s performance (Keller et al, 1987).

Another interesting finding of the present study was that most injuries occurred during training rather than during a game, results which are in accordance with Augustsson et al (2006). This result seems logical since players spent more time training than competing. The results also revealed that a higher injury incidence rate has been observed during the competitive period related to the preseason period and the post season period. This finding might be due to the fact that the training load in the competitive period is usually bigger and requires more effort resulting in generally more severe fatigue. These high demands make athletes function under more pressure not only physically but also psychologically, resulting in anxiety and tension (Andersen, 2001).

CONCLUSION
The main finding of this study was that almost half of the male volleyball players sustained one or more injuries during the season. The prevalence of injuries for youth and junior athletes was lower than that for seniors. The results also revealed differences in injury occurrence rate when the total exposure time for each age category has been taken under consideration. The authors suggest that any findings in injury occurrence rate must be interpreted in relation to the total exposure time in order to have more realistic conclusions.

Age was not an important factor influencing injury incidence related to the severity of injury or the season that it occurred. Important factors related to injury occurrence were ‘step on other’s foot’ and ‘incorrect sprawls’ while more injuries were sustained by outside hitters, middle hitters and universals. Finally, the majority of injuries were of moderate severity, were ankle sprains and occurred during training, and during the competitive period.

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