Kendo Headgear Concussion Safety Evaluation

Abstract: Concussions present a potential risk in various contact sports, including the martial 
art of kendo. While there are regulations implemented on the production quality of shinai, 
the bamboo-based swords used in kendo, there is a lack of active standards enforced by an 
independent governing body for kendo armor to prevent head injuries like concussions. 
Interestingly, two separate independent governing bodies exist to regulate and ensure the 
quality of commercially-sold shinai, but none for armor. This study aimed to answer two 
important questions: firstly, whether high-end kendo helmets offer superior protection 
against concussions compared to entry-level helmets, and secondly, whether adding extra 
padding inserts to the helmets enhances overall concussion protection. To conduct the study, 
we asked several kendo practitioners and one non-practitioner to deliver a series of head 
strikes using a shinai on a mannequin wearing different kendo helmets, both with and without 
additional protective padding. Our objective was to measure the force of each strike and 
assess the associated risk of concussion. The results indicated that both types of helmets 
sustained linear accelerations well below the threshold for the risk of concussion, which is 
set at 62.4g force. Notably, there were no statistical differences regarding impact forces 
received between the helmets (p-value equals 0.13). Interestingly, we found that commercial 
helmet padding inserts did not significantly reduce the risk of concussion. In fact, one of the 
commercially made helmet inserts performed worse than using a helmet alone (p-value is 
less than 0.01). In summary, our study suggests that investing in an entry-level kendo helmet 
with a 4-mm stitch pattern can offer comparable concussion protection to a high-end helmet 
with a 2-mm stitch pattern. As for commercially available padding inserts, their potential to 
provide additional concussion protection remains inconclusive and further studies are 
needed. Implementing a standardized evaluation process can aid consumers in making 
informed decisions when selecting protective gear to prevent concussions. 

Keywords: Kendo; Concussion; Sports Safety; Kendo Gear