Prevalence and burden of overuse injuries in elite junior handball

Inclusion

This was a 34-week prospective cohort study involving junior male handball players (aged 16–18 years) in South-Eastern Norway during the 2016–2017 season. A total of 11 teams were invited to participate in the study, and 10 teams (n=157) agreed to participate (figure 1). The teams were a convenience sample based on their geographical location, and defined as elite level based on their results from a youth Norwegian championship series the previous season. All included teams play in regional series consisting of six to eight teams from three Norwegian counties, and most also participate in an elite nationwide weekend series. Furthermore, a large proportion of players also compete in regional or nationwide series at a senior level.

Request permission

In September 2016, we visited each team during a training or match session and invited every player to participate in the study. Participation was voluntary, and all players and coaches received oral and written information about the study’s aims and procedures. Written consent was obtained from all players agreeing to participate, or their guardians (n=145).

Baseline questionnaires

Each player completed a baseline questionnaire containing questions about their height, weight, playing position, dominant jumping leg and throwing arm, numbers of years playing handball, whether they were a member of the national junior handball team, and how many teams in the club they represented. Players were also asked whether they had experienced shoulder, elbow, knee and/or lumbar spine problems during the previous season, and whether they had any current or long-term injuries that prevented them from participating in normal handball activity.

Injury registration

To record injuries, the OSTRC-O was distributed to all players every second Sunday from September 2016 to April 2017, 16 times in total. The questionnaire consists of four questions per anatomical area on the consequences of overuse injury on sports participation, training volume and sports performance, as well as pain (shown for the knee in figure 2). These four questions were repeated for the dominant and non-dominant shoulder, the dominant and non-dominant elbow, the dominant and non-dominant knee, and the low back. The questionnaire also recorded the number of hours of handball training, strength training and alternative training, and the number of match minutes completed in the previous 2 weeks.

Request permission

Online survey software (SurveyXact V.8.2, Rambøll Management Consulting, Oslo, Norway) was used to distribute the questionnaire to players by email. The software automatically sent a reminder to non-responders each day for 3 days, using a combination of emails and short messaging service. We revisited all teams in December 2016 to encourage players to respond to every survey, and were in regular contact with coaches in order to maximise the response rate.figure 2 (Approximately here)

Outcome measures

Players were defined as having an overuse problem in a particular anatomical area if they recorded any reduced handball participation, training volume or performance, or pain. They were defined as having a substantial overuse problem if they reported moderate or severe reductions in training volume or in performance, or complete inability to participate in handball.6

Each week, we calculated the prevalence of all overuse problems and substantial overuse problems for each anatomical area by dividing the number of players reporting problems by the number of questionnaire respondents. This was monitored throughout the season, and at the end of the study we calculated the average prevalence of all problems and substantial problems in each area, as well as the 95% CI. Data collected in the first week were not included in the summary measures, as per previous recommendations.6

Additionally, we calculated a severity score from 0 to 100 for each anatomical area for every questionnaire response, using previously described methods.6

At the end of the study, all severity scores were summed in each area in order to reflect the relative burden of overuse injuries as the proportion of the total severity score in each area represented.17

Statistical methods

When comparing average prevalence measures, statistical significance (α=0.05) was assumed if the 95% CIs did not overlap.

In order to determine whether players who were injured at baseline were more or less likely to respond to the questionnaires, logistic regression analyses were performed, using symptoms of injury at baseline as an independent variable and a 100% response rate as a dependent variable.

Participants

Sixty-one per cent of the sample was 17 years old, 33% 18 years old and 6% 16 years old. Eighty-nine per cent of the cohort was right-handed and 88% used their left leg as their dominant jumping leg. Fifty-five per cent of the players participated on two different teams (senior/junior) (n=80), 28% on one team (n=41) and 17% on three teams (n=24). Fourteen (10%) players were currently playing for the junior national team. The average player height was 184 cm tall (SD 7, range: 172–198 cm) and weighed 80 kg (SD 11, range: 60–115 kg), and had been playing handball for 9 years (SD 2, range: 4–14 years).

Pain and injuries at baseline

Twenty players (14%) reported that an overuse problem in the shoulder, elbow, knee or low back areas affected their current participation in handball training or matches at baseline.

Handball exposure

The median weekly amount of training performed during the study was 14 hours. This consisted of approximately 6 hours of handball training, 4.5 hours of strength training, 3 hours of alternative training and 30 min of handball match play (range: 0–200 min).

Response rate

The overall response rate to the OSTRC-O was 78% and complete data were collected from 48% of the players. Sixty-eight per cent of the sample completed 12 questionnaires or more. No associations were identified between players’ baseline injury status and their overall response rate.

Prevalence of overuse injuries

The average prevalence of all overuse injury problems across all anatomical areas was 39% (95% CI 29% to 49%). The average prevalence of all substantial overuse injury problems across all anatomical areas was 15% (95% CI 13% to 17%), and the highest average prevalence was reported in the shoulder (table 1). Ninety-one per cent of the players reported some type of overuse injury problem at some point during the season in either of the predetermined areas, and nearly half (48%) reported a substantial problem. Visual inspection of prevalence charts showed the injury prevalence was stable throughout the season for all injury outcomes (tables 2 and 3).

Methodological considerations

The main strengths of this study were the use of a sensitive injury registration method to capture the extent of overuse injuries. Previous studies of young handball players have used time loss definition and incidence-based measures, hence underestimated the prevalence of overuse injuries.7 9 Our approach used an all-complaints definition and recorded the consequences of injury beyond time loss, more appropriate for capturing overuse injuries.6 8

Additional strengths of this study included its full-season duration, its relatively large sample size and the high response rate to the questionnaire. Furthermore, we differentiated between dominant and non-dominant anatomical areas, which can help explain the full burden of overuse injuries among junior players more thoroughly than previous studies.

Limitations

There are several methodological limitations to consider when interpreting this study’s results. First, our injury registration was based only on players’ self-assessment of their pain, and its impact on their participation, training volume and sports performance. We did not attempt to confirm specific diagnoses using clinical assessments, which would have strengthened the data. Relying on self-reports meant that we were unable to confirm that the correct anatomical location was assigned, or whether all reported problems were indeed overuse injuries. Although we provided players with detailed definitions, instructions and examples, it is possible that some acute injuries were misclassified as overuse, or that some overuse injuries were not recorded.

A second methodological limitation is that, in using a broad ‘all physical complaints’ injury definition, we may have classified some cases of ‘normal’ pain related to athletic participation, such as delayed-onset muscle soreness, as overuse injury. Therefore, to filter out the minor cases with little functional consequences, we also used a substantial overuse injury definition.

Using this study design, we may not have recorded the full extent of overuse injuries affecting this cohort, as we only recorded injuries in a limited number of predefined anatomical areas. We chose to focus on problem areas previously found to be common sites of overuse injury among senior handball players,9 19 as well as the elbow, due to reports from coaches, players and clinicians working with handball players. However, other studies have reported anterior tibial pain to be common among junior and senior players,12 20 which would have been missed in the current study.

The final limitations of this study were that we only included junior male players, who have previously been found to have a higher injury risk than junior female players,11 12 and we did not consider the relationship between training loads and injury. Future studies of junior handball players should address these questions.

Perspective

The prevalence of overuse injuries among junior male handball players is high, particularly in the shoulder and the knee. Our results reiterate the importance of preventative measures in the sport of handball and shed new light on the burden of overuse injuries among male junior handball players.7 9 12 14 19 21 22

A large proportion of overuse injuries lead to reduced handball participation, training volume and performance during a critical developmental period. The development of effective prevention strategies for overuse injuries among junior male handball players should therefore be a priority.