Friday December 19 2008
Mathematical techniques were used to estimate the risk of injuries
Several newspapers have covered a story warning of the dangers of headbanging. The Daily Telegraph said it can “cause whiplash and stroke at tempos above 130 beats per minute”. The Daily Mail reports that headbanging, which involves “violently rocking your head back and forth to loud music”, is not only silly but also dangerous. It said a study on the subject has found that the faster a song is the greater chance of a neck injury.
This study was published in the British Medical Journal, which traditionally publishes tongue-in-cheek articles in its Christmas edition. The researchers apparently first became interested in headbanging after hearing anecdotal reports of headbanging-related injuries. To investigate this, the professor and a researcher attended a number of live music concerts to observe the head motion of headbangers. Complex mathematical techniques that are usually applied to car crashes were then used to estimate the risk of injury.
The researcher’s recommendation that headbangers substitute heavy metal music for adult-oriented rock and easy listening music is unlikely to be taken into consideration.
Where did the story come from?
The research was carried out by Declan Patton, a research assistant, and Andrew McIntosh, an associate professor from the School of Risk and Safety Sciences at the University of New South Wales, Sydney, Australia. Patton lists his musical interests as Jimi Hendrix and Led Zeppelin on the University of New South Wales website. McIntosh is interested in the effectiveness of sports headgear but doesn't list any musical interests.
The researchers were unable to persuade anyone from public, commercial or not-for-profit sectors to fund the research. The study was published in the British Medical Journal.
What kind of scientific study was this?
Both researchers visited rock concerts as part of this study, which was mainly descriptive. The researchers also used some focus group methods and biomechanical modelling to investigate the risks of mild traumatic brain injury and neck injury associated with headbanging. There were no measured outcomes or control groups. However, two scores were derived from observations and some assumptions about how the head and neck moves in the most common headbanging style that the researchers observed when visiting “several” hard rock and heavy metal concerts.
Concerts included as part of the study included Motörhead, Mötley Crüe, Skid Row, The Hell City Glamours, L.A. Guns, Ozzy Osbourne, Winger, Ratt, Whitesnake and W.A.S.P. Observations were conducted by watching anyone who seemed to be dancing. The researchers concluded from this that the “up-down headbanging style” was the most common. It is not clear how long the headbanging was observed for or the number of people that were observed.
The study also involved listening to music and asking local musicians - “a focus group” - to tap out the beat of 11 songs the group chose. These musicians were not selected for their musical training or talent. Using the focus group results, the researchers constructed a theoretical model to examine the effect of the head and neck motion. The song list, perhaps for legal reasons, is not reported. However, as a matter of interest, the researchers did compare the tempo of these songs with three others: I Will Always Love You by Whitney Houston, Hello by Lionel Ritchie, and Babe by Styx. It is assumed these songs were slower but no average tempo is given for them in the report.
Mathematical models were then used to produce a score for the risk of head or neck injury from acceleration and speed inputs. These models have previously been used in crash tests in trains and cars. The head injury criteria (HIC) ranges from zero to 1,200 depending on the tempo and anything between 135 and 519 is linked with headache and dizziness in the train crash research. The neck injury criteria (NIC) score is derived in a similar way by a mathematical formula that relates the acceleration and velocity of the head’s centre of gravity relative to the first thoracic vertebra.
What were the results of the study?
The researchers say that an average headbanging song has a tempo of about 146 beats per minute (bpm). They predict that this could cause mild head injury (135 HIC), a score linked to headache and dizziness when the range of motion is greater than 75 degrees in the up and down direction.
The risk of neck injury begins at tempos of 130 bpm and this is also related to the range of motion of headbanging. Fast tempo songs can have an underlying rhythm of 180 bpm. The songs, such as Spinal Tap’s Tonight I’m Gonna Rock You Tonight and Kickstart My Heart by Mötley Crüe, could be combined with a 120 degree range of neck movement and theoretically lead to a high risk of neck injury (NIC score of 15m2/s2). This exceeds a proposed limit for human tolerance.
What interpretations did the researchers draw from these results?
The researchers are quoted as saying that to minimise the risk of head and neck injury, headbangers should “decrease their range of head and neck motion, headbang to slower tempo songs by replacing heavy metal with adult-oriented rock, only headbang to every second beat, and use personal protective equipment such as neck braces to limit range of motion.”
What does the NHS Knowledge Service make of this study?
As in all good studies, the researchers list some limitations that they consider might affect the interpretation of their mathematical model of musical motion.
They say that the HIC and NIC are designed to analyse single acceleration peaks such as those that occur in crashes and not the repetitive motion of headbanging. This seems to be a major problem with the methods. The researchers see a way around it and propose to scale down the results, but didn’t actually do this.
The interventions to minimise injury are intriguing and the researchers elaborate further on what they mean by replacing heavy metal with adult-orientated rock. They list artists such as Michael Bolton, Celine Dion, Enya and Richard Clayderman, and then call for future randomised controlled trials of these musical substitutes.