Neck Strength and Head Impacts in Ice Hockey

Study Title: Does cervical muscle strength in youth ice hockey players affect head impact biomechanics?
Authors: JP. Mihalik, KM. Guskiewicz, SW. Marshall et al.
Journal: Clinical Journal of Sport Medicine
Date: September 2011


Summary:

• Some of you are aware that Hockey Canada recently instituted their new Head Contact Rule in an attempt to minimize head and neck injuries, including concussions. While I think this is certainly a giant leap in the right direction, there are also many other factors to consider when it comes to injury prevention. In this particular study, Mihalik and his group of researchers looked at the role of more "internal factors" for head injury prevention, specifically cervical muscle strength. The rationale for this paper was based on the speculation that the neck can be strengthened to reduce the risk of mild traumatic brain injuries by way of tension to withstand and distribute the force of head impact.
• This prospective cohort study utilized AAA hockey players (aged 15 + 1 year) wearing helmets equipped with Head Impact Telemetry to record impact force data (linear, rotational and HIT severity profile) in real-time. Using a handheld dynamometer, body relative cervical muscle strength (as described by Kendall) of the anterior neck flexors, anterolateral neck flexors, cervical rotators, posterolateral neck extensors, and upper trapezius were measured. These results were then used to categorize the players into three groups based on strength (weak, moderate and strong) for the purposes of comparative analysis.
• Of the 7770 total impacts recorded over the course of one season, it was revealed that increased isometric cervical strength did not reduce the severity of head impacts. In fact, those players with weaker upper trapezius muscles experienced lower impact severity scores than those with the strongest recordings.
• Personally, I am not prepared to discredit the role of neck strengthening as a potential protective mechanism but I do think some things (relevant to this aspect of injury prevention) need to be considered. First, I am not quite sure how the results from a shrugging maneuver (as used to test the upper trapezius) can be relevant regardless of the findings. I would put more weight into those results from each of the other testing procedures. Second, I'm more of a quality of muscle activation kind of guy rather than a quantity. Does quantity matter? Of course, but I do think that the ability to reflexively stabilize a joint upon impact is more important than absolute strength. I would liked to have seen Janda's and Jull's tests rather than the ones used. Finally, we should remember that the results of this paper are demographic specific. At this age, the players are not only still developing physically, but they are also still learning the art of both rendering and receiving contact. Therefore, I would like to see a similar study performed at higher levels and at the very least, in junior age players.

Mihalik, JP et al. (2011). Does cervical muscle strength in youth ice hockey players affect head impact biomechanics? Clinical Journal of Sport Medicine, vol 21(5); 416-421