Kendo Headgear Concussion Safety Evaluation

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.

I. Introduction

Sports-related concussions have recently gained much attention, particularly with regard to prevention and management. Efforts to prevent such concussions, seen primarily in contact sports like rugby and soccer, have been implemented, including revising and creating guidelines for injury recovery^1,2. A study analyzing data from the National Collegiate Athletic Association (NCAA) in the US reported a higher incidence of sports-related concussions in contact sports such as wrestling, ice hockey, and American football³. Other studies investigating brain damage resulting from these types of concussions have also been conducted, such as measuring head impact using accelerometers⁴ or estimating brain injury risk through video analysis⁵. Mechanisms of concussion have also been explored using a baseline evaluation or blood biomarkers^6,7. However, most published studies on sports-related concussions have historically focused more on NCAA-sanctioned sports, such as American football and rugby. Few studies have been described in Western literature for the prevention of concussion in lesser-known Japanese contact sports, such as kendo (the Japanese art of fencing) and judo (the Japanese art of unarmed combat)⁸. Even in Japan, concussions are not well reported or studied in kendo⁹. Although these sports continue to cause numerous head injuries annually, research efforts have not been as extensively conducted in these sports¹⁰.