Led Zeppelin's immortal song Dazed and Confused might well have been a clinical observation on the state of their audience's brains, say Australian researchers who have found over-enthusiastic head-banging can cause mild brain injury.

In a study published in this week's Christmas issue of the British Medical Journal, two University of New South Wales (UNSW) researchers concluded that head-banging to a typical heavy metal tempo could cause mild traumatic brain injury or concussion, and neck injury, particularly as the tempo of the music and angle of movement increased.

"Clearly it's a serious issue," says Prof. Andrew McIntosh, co-author and professor of biomechanics at UNSW.

"If you observe people after concerts, they clearly look dazed, confused and incoherent, so something must be going on and we wanted to look into it."

Beats per minute

After careful observation of the behaviour of heavy metal concert-goers, McIntosh and honours student Declan Patton constructed a theoretical head-banging model to better understand the mechanics of the practice.

They also spoke to a focus group of local musicians to identify 10 popular songs to head-bang to.

"These songs had an average tempo of 146 beats per minute, and at this tempo we predict that head-banging can cause headaches and dizziness if the range of movement of the head and neck is greater than 75 degrees," the researchers wrote.

Several songs were selected as controls against which to compare the risk of heavy metal head-banging, including Whitney Houston's I Will Always Love You.

But McIntosh said attempts to find control cases of head-banging at alternative venues, such as Andre Rieu concerts, were unsuccessful.

Risky observations

Unfortunately for McIntosh, who confesses to not being a heavy metal fan, the research involved attending several heavy metal concerts of bands including Motley Crue, Ozzy Osbourne and Motorhead to identify the most popular head-banging techniques and better understand the biomechanics of the movement.

Despite being an observational study only, McIntosh said there were considerable occupational health and safety issues involved for researchers, including the risk of hearing damage and the potential adverse outcomes of dealing with excited patrons who may have been "under the influence of things."

McIntosh, whose research focuses on the biomechanics of head injury and concussion, said this type of temporary, mild brain injury was generally poorly understood, but was unlikely to lead to any more serious symptoms than headaches and dizziness.