XT Guardian Caps do not reduce the risk of sport-related concussions in high school football players
By Anni Yurcisin. This article was initially published in the 11/6/25 edition of our Concussion Update newsletter; please consider subscribing.
In the East Bay in California, several high school football players sustained a concussion in one Friday night game, with one player having to be wheeled off on a stretcher, according to an NBC Bay Area article by Pete Suratos. Parents struggled with watching their kids get injured, looked for a lifeline to prevent concussions, and decided on Guardian Caps. Although they haven’t been proven to reduce concussions in high school football players, parents have been raising money to buy one for every player.
A recent study in the British Journal of Sports Medicine found that Guardian Caps (GCs), an add-on padded “shell device” that goes atop a helmet, do not reduce the risk of sport-related concussions (SRCs) in high school football players. Across more than 2600 high school football players, GC use during practice was not associated with decreased SRC risk in practices or in games, including when accounting for the increased risk factor of having sustained an SRC in the past. While laboratory experiments have shown that extra padding, such as GCs, can limit simulated head impact forces, and previous data from the NFL have shown a decrease in preseason concussions with GC use, no previous studies have looked at the real-world efficacy of high school GCs, which, notably, are a different model from those used in the NFL. The GCs worn in the NFL (the NXT model) weigh approximately 357 grams and are approximately 2.5 cm thick, while those worn by high schoolers (the XT model) weigh approximately 220 grams and are approximately 1.5 cm thick. Because of this difference, NFL studies cannot be extrapolated to high school athletes. This study illustrates that there is no evidence to suggest that the XT model GCs used by high school athletes reduce SRCs. Importantly, as Dr. Erin Hammer told the UW-Madison School of Medicine and Public Health, “... using these devices may provide false reassurance to players and their parents who are hoping to reduce their kids’ risk of concussion.”
Of the 180 SRCs recorded throughout the year by athletic trainers, 64 occurred during practice and 116 occurred during games. The number of SRCs occurring in practice was remarkably similar between GC-wearing and non-GC-wearing athletes; 33 of the practice-related concussions were in athletes wearing GCs, while 31 practice-related concussions were in athletes not wearing GCs. In what is standard practice among football players who wear GCs, athletes who wore GCs during practices did not wear them during games. Of the 116 game-related concussions, 68 occurred in athletes who wear GCs at practice, and 48 occurred in those who do not.
The authors urge sport-related institutions to implement evidence-based changes to reduce SRCs rather than pursuing new technologies that haven’t been proven to reduce SRCs in non-laboratory settings, such as GCs. They highlight three changes that have been connected to a reduction in SRCs: policies aimed at limiting contact in football practices (which reduced the rate of practice-related SRCs by 64%), coach participation in a comprehensive football safety training program (which reduced the rate of practice and game-related SRCs by 50%), and modifications to helmets with increased padding in targeted areas (which were associated with a 31% lower rate of SRC). These changes, while less flashy than technologies like GCs, have been proven to decrease the risk of SRC and should be the targets for high school leagues to improve the cognitive health of their athletes.
