The Throwing Shoulder: The Cause of Shoulder Injuries or Pain in Experienced Handball Players: Nordic Throwing Shoulder Project (NTS - Project)

For a trainer or a coach in sports, it is very important to know what determines performance and how to affect the performance by training. However, training can also cause injuries by using wrong techniques or too much overload. One of those injuries in handball (one of the biggest sports in Scandinavia) is shoulder pain. Besides handball, shoulder pain and injury is reported to be a large problem in athletes in other overhead sports such as baseball, javelin, tennis, badminton, volleyball. In handball 44-75% of the athletes had a history of shoulder pain and a weekly prevalence of shoulder problems in 28% of the athletes. While in baseball half of the youth baseball pitchers prevalence shoulder pain during the season. Shoulder pain has been reported to have an impact on the athletes' training activities, performance, and daily life.

Several studies have investigated risk factors for shoulder injuries among overhead athletes, with particular focus on glenohumeral joint range of motion (ROM) and shoulder strength. and scapular control.

In handball it was found that reduced glenohumeral internal rotation and excessive glenohumeral external rotation have been suggested as risk factors and that a reduction of total glenohumeral rotation has been associated with shoulder problems. Regarding rotator cuff strength, external rotation weakness and low ratios of concentric and eccentric external to internal rotation strength have been reported as risk factors in handball and baseball. In addition, weakness in glenohumeral abduction strength has been associated with shoulder injury in baseball. However, in a recent study of van Cingel the glenohumeral internal range of motion deficit and total range of motion deficit in elite female handball players seemed not to be risk factors for shoulder injuries.

However, sports injury research needs to move from simple analyses of risk factors and concentrate on how these factors interact among other determinants for injury. Athletes in overhead sports require a subtle balance of shoulder stability and mobility in order to meet the functional demands of their respective sport. It has been reported that altered shoulder mobility in these athletes is caused by adaptive structural changes to the joint because of the extreme physiological demands of the overhead activity. Nonetheless, it is not known if these possible changes that are necessary for high performance also cause injuries. Injury occurrence results from a combination of possessing these different risk factors and participating with these risk factors. Mostly it is a combination of possessing these risk factors and the amount of throwing that causes injuries. Thereby training overhead sports must be considered a primary risk factor for shoulder injury, while non-participation-related risk factors like strength, glenohumeral ROM and scapular control influence the amount of handball participation a player can tolerate before shoulder injury occurs. Møller showed in a 31-week cohort study of elite youth handball players that an increase in handball load by >60% was associated with greater shoulder injury rate. Furthermore, the effect of an increase in handball load between 20% and 60% was worsened among players with reduced external rotational strength or scapular dyskinesia.

However, none of the above mentioned studies investigated kinematics of throwing, which perhaps could be the most important risk factor for shoulder injuries.