We conducted an observational study to identify the most popular head banging technique. We attended several hard rock and heavy metal concerts to find the most common style of head banging executed by audience members. The bands performing at these concerts included Motörhead, Mötley Crüe, Skid Row, The Hell City Glamours, L.A. Guns, Ozzy Osbourne, Winger, Ratt, Whitesnake, and W.A.S.P. It was evident that most people engaging in head banging chose to perform the up-down style.
Using the results of the observational study, we undertook biomechanical analyses. Previous studies have shown that angular head velocity, and therefore also angular displacement and acceleration, during head oscillation in pitch are approximately sinusoidal.15
Therefore we constructed a theoretical head banging model with the basic assumption that the angular displacement of the head during head oscillation in pitch follows a sinusoidal motion in the sagittal plane with the T1-C7 joint acting as the axis of rotation. We used reported coordinates of the centre of gravity of the head and the T1-C7 joint for a 50th centile adult male (table 1) and calculated the radius of rotation of the head to be about 174.0 mm.
Coordinates of head’s centre of gravity (CG) and C7-T1 joint for a 50th centile adult male16 17
The amplitude of the displacement curve was based on the range of motion of the cervical spine of an adult male—60.4° flexion and 69.9° extension,—giving a total of 130.3°.18
Therefore we varied the range of motion from 45° to 120° by increments of 15° to investigate the effect that the range of motion has on injury severity.
We varied the range of angular displacement of the head and neck and the frequency of the movement in the theoretical model and derived Head Injury Criterion (HIC) and Neck Injury Criterion (NIC) levels (see equations 1 and 2, respectively). HIC was related to the abbreviated injury scale and established injury thresholds (table 2). It is recognised that there are limitations in the interpretation of HIC in the absence of a direct head impact.
Table 2 Abbreviated injury scale (AIS), Head Injury Criterion (HIC), and symptoms of head injury19
Where t1 and t2 are the initial and final times of the interval during which the head injury criteria attains a maximum value and a(t) is the resultant acceleration measured at the centre of gravity of the head.
The originally proposed human tolerance for NIC was 15 m2
Several studies, however, disagree with this, as people have experienced neck injury when the measured criteria never exceeded 15 m2
This threshold is now used for long term symptoms,22
and a more recent study proposed 8.7 m2
as a threshold for acute soft tissue injury.23
Where arel and vrel are the acceleration and velocity of the head’s centre of gravity relative to the T1 vertebra.
We asked a focus group of 10 musicians from local bands to nominate their favourite head banging song. Musical training or talent was not a prerequisite for membership of this group. The focus group voted on each song, and we compiled an ordered list of the top 11 songs. As each song was played, members of the focus group were asked to tap out the beat of the song for the duration of one minute, so we could calculate the average tempo of each song. We chose this rather than direct measurement of tempo because it reflects the head banger’s potential actions when exposed to this music.
We randomly selected three songs (“I Will Always Love You” by Whitney Houston, “Hello” by Lionel Ritchie, and “Babe” by Styx) from on-line lists of easy listening and adult oriented rock as musical controls.