Efficacy Of Soft-shell Padding On Head Impact Kinematics In American Football: Pilot Findings

PURPOSE: Soft-shell padding can be used to augment standard football helmets and is purported to reduce head impact severity. We aimed to determine if soft-shell padding reduces head impact kinematics a) among individuals that had not previously worn soft-shell padding, and b) between teammates with or without soft-shell padding. METHODS: We studied 15 offensive and defensive linemen and linebackers completing the 2021 fall college season. This included a group of players wearing soft-shell protective padding for the final 5 weeks of the season (SHELL; n = 10; height = 194.0 ± 3.6 cm; mass = 134.3 ± 10.6 kg), and a control group not wearing soft-shell padding (CONTROL; n = 5; height = 188.0 ± 6.5 cm; mass = 119.1 ± 12.1 kg). Helmets were instrumented with Head Impact Telemetry System to quantify peak linear (g) and rotational (rad/s2) accelerations. Among SHELL, we conducted a Wilcoxon signed-rank test to compare head impact kinematics between weeks 1-7 (without soft-shell padding) and weeks 8-12 (with soft-shell padding). We also compared SHELL and CONTROL groups with Mann-Whitney U-Tests across these outcomes during weeks 8-12. RESULTS: Two head impacts from SHELL and seven impacts from CONTROL were statistical outliers (linear acceleration > 80 g) and removed from dataset. Within SHELL, there were no significant differences (Z = -.096; p = .924) in linear acceleration between weeks 1-7 (n = 2176; median [interquartile range]: 21.8 [14.2] g and weeks 8-12 (n = 755; 22.1 [15.3] g). A similar finding was observed for rotational acceleration (Z = .354, p = .552; weeks 1-7: 1464.2 [922.9] rad/s2; weeks 8-12: 1478.7 [1153.3] rad/s2). There were no differences in linear acceleration (U = 1.926, p = 0.185) during weeks 8-12 between SHELL (n = 755; 20.8 [14.0] g) and CONTROL (n = 392; 22.1 [15.3] g) groups. We observed a similar trend for rotational acceleration (U = 0.073, p = 0.835; SHELL: 1493.2 [1014.5] rad/s2; CONTROL: 1478.7 [1153.3] rad/s2). CONCLUSIONS: Based on the findings of our pilot study, soft-shell padding did not reduce head impact severity. Future studies should consider video-confirmed impacts to examine practice characteristics (individual vs team drills) to further evaluate the football specific contexts in which soft-shell protective padding may best reduce head impact burden for athletes who choose to use them.