Guardian Caps (GCs) are currently the most popular external helmet-add on designed to reduce the head impact magnitude experienced by American football players. GCs have been endorsed by influential professional organizations, however few studies evaluating the efficacy of GCs are publicly available.


The objective of this study is to present preliminary on-field head kinematics data for NCAA Division I American football players using instrumented mouthguards through closely matched pre-season workouts both with and without GCs.


Case Series


The study took place during the 2022 American football pre-season

Patients or Other Participants

25 Male NCAA Division I student-athletes participating in American football completed some portion of the 6 workouts included in this study. Of the 25 total participants, 7 completed all 6 workouts using their instrumented mouthguards.

Main Outcome Measure(s)

The peak linear acceleration (PLA), peak angular acceleration (PAA) and total impacts were collected using instrumented mouthguards (iMG) during 3 pre-season workouts using traditional helmets (TRAD), and 3 with Guardian Caps used in additional to a traditional helmet (GC). The TRAD and GC values for PLA, PAA and total impacts were analyzed using ANOVAs.


There was no significant difference between the collapsed mean values for the entire sample between TRAD and GC for PLA (TRAD=16.3±2.0, GC=17.2±3.3Gs; p=0.20), PAA (TRAD=992.1±209.2, GC=1029.4±261.1rad/s2; p=0.51 and the total amount of impacts (TRAD=9.3±4.7, GC=9.7±5.7; p=0.72). Similarly, no difference was observed between TRAD and GC for PLA (TRAD=16.1±1.2, GC=17.2±2.79Gs; p=0.32), PAA (TRAD=951.2±95.4, GC=1038.0±166.8rad/s2; p=0.29 and total impacts (TRAD=9.6±4.2, GC=9.7±5.04s; p=0.32) between sessions for the7 repeated players.


These data suggest no difference in head kinematics data (PLA, PAA and total impacts) when GCs are worn. This study suggests GCs may not be effective in reducing the magnitude of head impacts experienced by NCAA Division I American football players.

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Author notes

1aE-mail address: (Kristen G Quigley)

1bE-mail address: (Dustin Hopfe)

1cE-mail address: (Madison Fenner)

1dE-mail address: (Philip Pavilionis)

1eE-mail address: (Vincentia Owusu-Amankonah)

1fE-mail address: (Nicholas G Murray)