Head and neck control varies with perturbation acceleration but not jerk: implications for whiplash injuries

Abstract

Recent studies have proposed that a high rate of acceleration onset, i.e. high jerk, during a low-speed vehicle collision increases the risk of whiplash injury by triggering inappropriate muscle responses and/or increasing peak head acceleration. Our goal was to test these proposed mechanisms at realistic jerk levels and then to determine how collision jerk affects the potential for whiplash injuries. Twenty-three seated volunteers (8 F, 15 M) were exposed to multiple experiments involving perturbations simulating the onset of a vehicle collision in eyes open and eyes closed conditions. In the first experiment, subjects experienced five forward and five rearward perturbations to look for the inappropriate muscle responses and 'floppy' head kinematics previously attributed to high jerk perturbations. In the second experiment, we independently varied the jerk (∼125 to 3 000 m s −3 ) and acceleration (∼0.65 to 2.6 g) of the perturbation to assess their effect on the electromyographic (EMG) responses of the sternocleidomastoid (SCM), scalene (SCAL) and cervical paraspinal (PARA) muscles and the kinematic responses of the head and neck. In the first experiment, we found neither inappropriate muscle responses nor floppy head kinematics when subjects had their eyes open, but observed two subjects with floppy head kinematics with eyes closed. In the second experiment, we found that about 70% of the variations in the SCM and SCAL responses and about 95% of the variations in head/neck kinematics were explained by changes in perturbation acceleration in both the eyes open and eyes closed conditions. Less than 2% of the variation in the muscle and kinematic responses was explained by changes in perturbation jerk and, where significant, response amplitudes diminished with increasing jerk. Based on these findings, collision jerk appears to have little or no role in the genesis of whiplash injuries in low-speed vehicle crashes.

Seated postural neck and trunk reactions to sideways perturbations with or without a cognitive task

“…The larger peak angle displacements in seated participants due to higher accelerations conform to earlier research (Siegmund and Blouin, 2009;Siegmund et al, 2002). However, some of the differences can be due to perturbation characteristics.…”

“…Postural reactions in the neck or trunk due to perturbations in seated positions depend on several factors attributed to the perturbation characteristics, such as the amplitude and direction (Masani et al, 2009;Preuss and Fung, 2008;Sacher et al, 2012;St-Onge et al, 2011;Zedka et al, 1998), acceleration (Kumar et al, 2004a;Siegmund and Blouin, 2009;Siegmund et al, 2002) and complexity (Xia et al, 2008). Other factors are awareness of an upcoming perturbation (Siegmund et al, 2003a) and the initial posture (Kumar et al, 2005;Kumar et al, 2006).…”

Effects of Bracing on Human Kinematics in Low-Speed Frontal Sled Tests

“…2,3,5,9,11,12,15,16,19,30,37,43,45,51,55,56,58 Of the multitude of human volunteer sled test series, few have examined the effects of bracing. 3,5,15,[30][31][32]37,45 The vast majority of studies examining the effects of muscle tension focus on either rear-end impacts or whiplash events, 11,12,43,48,[51][52][53]56 the response of the head and neck complex, 9,45,[58][59][60] or the response of the head and spine. 2,15 Of the studies that incorporate bracing in frontal sled tests, there is often a focus on the lower extremities.…”

Dynamic Spatial Tuning of Cervical Muscle Reflexes to Multidirectional Seated Perturbations

“…9 , 10 Despite the increasing complexity of these muscle recruitment schemes, most models assumed equal activation levels for all muscles within presumed agonist or antagonist groups. 1 , 2 , 11 , 12 Electromyographic (EMG) activity in the cervical muscles of volunteers has been recorded during low-velocity impacts or perturbations, however most of these studies are confi ned to sagittal plane loading [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] with fewer studies assessing lateral or oblique loading. 11 Despite these various efforts to model active cervical muscle responses, few of the proposed activation schemes are based on or compared with experimental data from in vivo recordings of muscle activation before and during loading.…”