Handball is one of the sports that are encompassed by the term overhead, a concept that includes sports based on a movement in which the arm is brought above the head. Although this is typically associated with the action of throwing, it also refers to other sports such as swimming or tennis, which may result in very similar injuries.

Knowing the muscle activation order in shoulder movements can be important when it comes to identifying injury risk or implementing rehabilitation exercises. Especially if we take into account the likelihood to get injured in the event of a scapular dyskinesis, or increasing training load which results in fatigue. Scapular dyskinesis and fatigue have been associated with the alteration of muscle activation order patterns; potential alteration of these activation patterns and movements which could increase the risk of injury.

However, this pattern is not currently well known, nor if continued exercise, such as that performed by elite athletes, can entail differences in the activation order. A recent study published in the Physical Therapy in Sport journal, in which several members of the FC Barcelona Medical Department participated, has addressed this issue.

A Pioneering Study

There were 34 participants involved in the study: 14 of them were professional handball players, and the rest were healthy volunteers who were not involved in any particular physical activity. All patients underwent a standard shoulder examination based on three basic movements related to flexion, elevation and abduction movements. Also, the activation order of the various muscles involved was studied using a combination of electromyography techniques.

Once analysed, the results showed that the periscapular muscles were consistently activated before those of the rotator cuff, which were the last muscles to activate. “We did not find any differences in the activation order between professional overhead athletes and non-athletes, not in these three standardised movements, at least” explained Silvia Ortega, the club’s physiotherapist and first author of the study. “These movements have not shown any differences in activation time between overhead and non-overhead, which could either indicate that they do not exist, or that the movements used in physical examinations are not appropriate for assessing the differences, so we should assess other more functional and specific movements,” she concluded.

The study also analysed what neuromuscular implications occurred when different muscle groups activated through movements performed at different speeds and with different loads (a weight of 3 kg). “It would be logical to assume that the activation is faster when the movement effort is greater,” commented Ortega. “This is what we observed when the action was performed with a weight. Surprisingly, however, it did not occur when the movement was faster, but rather when it was performed at medium or low speed. We are not able to explain the reason why,” she admits, “but this information is useful for carrying out examinations and planning rehabilitation programs.”

Conclusions

The main conclusion of the study is that, during the movements used in the physical shoulder examination, “we haven’t found differences in the muscle activation order between professional handball players and people who do not practice a sport involving overhead action; therefore, the characteristic anatomical adaptations of overhead movements do not represent a change in the muscle activation order,” explained Ortega. This study has established the activation sequence, something that was not previously known with accuracy since “the studies had been based mainly on the amount of activation, but not so much on the activation time, and this is the first time that this has been done with handball players,” she emphasised. “We have also seen that activation is faster under load conditions and at medium speed,” which can be useful when creating rehabilitation programs.

Handball players with scapular dyskinesis, who supposedly present an alteration in their motor pattern, seem to have a higher risk of suffering from Subacromial Impingement Syndrome (SIS), especially when the training load increases. Identifying changes in the muscle activation order in players with SIS could be useful when comparing healthy players with others suffering from ailments and assessing possible risk indicators and activation behaviour in case of pain. This is the reason why “we are now studying pathology groups to determine whether there are differences. The results will soon be published,” confirmed Ortega.

The Barça Innovation Hub team