An envelope of linear and rotational head motion during everyday activities

Abstract

Various studies have characterized head kinematics in specific everyday activities by looking at linear and/or rotational acceleration characteristics, but each has evaluated a limited number of activities. Furthermore, these studies often present dissimilar and sometimes incomplete descriptions of the resulting kinematics, so the characteristics of normal everyday activities as a whole are not easily collectively summarized. The purpose of this study was to evaluate the literature investigating head kinematics associated with everyday activities and to generate a comprehensive kinematic boundary envelope describing these motions. The envelope constructed constitutes the current state of published knowledge regarding 'normally occurring' head accelerations. The envelope of kinematics represents activities commonly encountered and posing zero to minimal risk of injury to healthy individuals. Several kinematic measures, including linear accelerations, rotational velocities, and rotational accelerations, one may encounter as a result of normal everyday activities are summarized. A total of 11 studies encompassing 49 unique activities were evaluated. Examples of activities include sitting in a chair, jumping off a step, running, and walking. The peak resultant linear accelerations of the head reported in the literature were all less than 15 g, while the peak resultant rotational accelerations and rotational velocities approach 1375 rad/s² and 12.8 rad/s, respectively. The resulting design envelope can be used to understand the range of acceleration magnitudes a typical active person can expect to experience. The results are also useful to compare to other activities exposing the head to motion or impact including sports, military, automotive, aerospace and other sub-injurious and injurious events.

Keywords: Brain injury; Daily head accelerations; Finite element model; Kinematics; Strain.

Fig. 1

Schematic displaying three coordinate directions (a) and assumed shape for the rotational acceleration pulse (b)

Fig. 2

Resultant linear acceleration for activities from all 11 studies

Fig. 3

Comparison of linear acceleration (a) and rotational acceleration (b) for walking and running and linear acceleration (c) and rotational acceleration (d) for the common activities between the five studies listed in the figure legend

Fig. 4

X, Y, Z, and resultant linear acceleration results from Allen et al. (1994), Exponent (2002), Kavanagh et al. (2004), Bussone (2005) and Carriot et al. (2014)

Fig. 5

Linear vs. rotational acceleration (a) and rotational velocity vs. rotational acceleration (b) for activities from six of the examined studies. Lines of constant duration (10 – 100 ms) are also displayed in b. *Linear acceleration was not available for activities from Bussone and Duma (2009), so all corresponding data is plotted on the x axis

Fig. 6

Rotational duration vs. rotational acceleration (a) and rotational duration vs. rotational acceleration with upper and lower bounds defining impact kinematics associated with everyday activities (b). Lines of constant rotational velocity (2 – 12 rad/s) are displayed in (a). Additionally, the range of rotational acceleration and pulse durations associated with the three distinct loading regimes are identified in (b). The size of the marker indicates the magnitude of linear acceleration for the respective activity

Fig. 7

Linear and rotational acceleration associated with everyday activities compared to those collected from youth football athletes (a) and rotational kinematics associated with everyday activities compared to those collected from youth football athletes (b). Additionally, published thresholds for DAI and published risk curves are included for reference (Rowson et al. 2012; Rowson and Duma 2013)