The contact nature of American football has made head acceleration exposure a concern. We aimed to quantify the head kinematics associated with direct helmet contact and inertial head loading events in collegiate-level American football. A cohort of collegiate-level players were equipped with instrumented mouthguards synchronised with time-stamped multiple camera-view video footage of matches and practice. Video-verified contact events were identified as direct helmet contact or inertial head loading events and categorised as blocking, blocked, tackling, tackled or ground contact. Linear mixed-effects models were utilised to compare peak head kinematics between contact event categories. The timestamp-based cross-verification of the video analysis and instrumented mouthguard approach resulted in 200 and 328 direct helmet contact and inertial head loading cases, respectively. Median linear acceleration, angular acceleration and angular velocity for inertial head loading cases was greater than direct helmet contact events by 8% (p = 0.007), 55% (p < 0.001) and 4% (p = 0.007), respectively. Median head kinematics for all contact event categories appeared similar with no pairwise comparison resulting in statistical significance (p > 0.05). The study highlights the potential of combining qualitative video analysis with in-vivo head kinematics measurements. The findings suggest that a number of direct helmet contact events sustained in American football are of lower magnitude to what is sustained during regular play (i.e. from inertial head loading). Additionally, the findings illustrate the importance of including all contact events, including direct helmet contact and inertial head loading cases, when assessing head acceleration exposure and player load during a season of American football.

美式足球的接触性使头部加速暴露成为一个问题。我们旨在量化与大学水平的美式橄榄球直接头盔接触和惯性头部负荷事件相关的头部运动学。一群大学水平的球员配备了器械护齿器，与带有时间戳的比赛和练习视频镜头同步。经视频验证的接触事件被识别为头盔直接接触或惯性头负荷事件，并被分类为阻塞，阻塞，定位，滑行或地面接触。线性混合效应模型用于比较接触事件类别之间的峰值运动学。视频分析和仪器化护齿方法基于时间戳的交叉验证分别导致200个和328个直接头盔接触和惯性头加载情况。惯性头部负荷情况下的线性加速度，角加速度和角速度的中值分别比头盔直接接触事件高8％（p = 0.007），55％（p <0.001）和4％（p = 0.007）。所有接触事件类别的头部运动学中位数似乎相似，没有成对比较，导致统计学意义（p> 0.05）。该研究突出了将定性视频分析与体内头部运动学测量相结合的潜力。研究结果表明，在美式橄榄球中发生的许多直接头盔接触事件的程度要低于常规比赛中发生的事件（即 来自惯性头负载）。此外，研究结果表明，在评估美式足球赛季的头部加速暴露和球员负荷时，包括所有接触事件（包括直接头盔接触和惯性头部负荷情况）的重要性。