The week in Biomechanics #CW18

The weekly recap of what is going on in the world of biomechanics.

This week we continue looking at interesting methods that have been used to gain insight on biomechanical effects during sports that can hardly be performed in a lab. After covering surfing and skateboarding last week, we here present you an awesome paper about the consequences of wearing a helmet during wakeboarding and water skiing on the head and neck injury potential. Enjoy the read!

1. Head and neck injury potential during water sports falls: examining the effects of helmets
2. 18. Staffordshire Conference on Clinical Biomechanics

Head and neck injury potential during water sports falls: examining the effects of helmets

Injuring your head or neck during wakeboarding or water skiing can be a result of collisions, either with obstacles, equipment or people. But also falling into the water, without impacting to a solid object, can become dangerous at higher speeds. Concerns have been expressed that wearing a helmet can increase the risk of injury in the latter type of falls, for example due to larger deceleration forces at the point of entering the water as a result of the larger cross-sectional area of a helmeted head. Furthermore, during a backward fall the helmet might act as a parachute anchor, dragging the head at the chinstrap (the effect is called “bucketing”) and lead to brain- and cervical spine injuries.

Obviously, examining these effects in a field study is pretty complex. Therefore the group of Irving S. Scher et al. came up with an exciting paper that was published in “Sports Engineering” two weeks ago. They used a 60 kg anthropomorphic test device (ATD, or a dummy), built a pendulum, and made their ATD swing into a pool. Have a look at the setup below:

With this setup, the group was able to mimic both backward and forward falls. The ATD was instrumented and quantified head accelerations as well as cervical spine loads during water entry using triaxial accelerometers and six-axis load cells. The speed just prior to water impact was measured using a laser speed trap. 3 types of helmets were tested (one of them a bicycle helmet), all varying in the number of vents available. That’s another interesting point since the number of vents is believed to have an effect on the strength of “bucketing”. Of course, also unhelmeted trials were conducted, plus testing at two different impacting angles. The speed at impact was 8.8 m/s, which is comparable to wakeboarder speeds in cable-tow parks.

If you are interested in the exact data processing and calculation of the Head Injury Criterion and drag coefficients we definitely encourage you to read the whole paper, it’s assuredly worth studying.

However, we’ll jump to the results here: Across all test configurations, head angular accelerations were less than 1000 rad/s², the likelihood of mild traumatic brain injury was under 1% and did not change significantly with helmet use. It is interesting to see that many of the injury metrics (such as cervical spine compression) increased significantly when a helmet was worn, yet the results were still below the injury assessment reference value.

In summary, it is a pretty good idea to wear a helmet while wakeboarding or water skiing. The increased parameters seen in the helmeted condition do not reach critical values, and impacts on hard, fixed objects or persons are probably a league by itself. We loved the creative methods used in this paper and really recommend reading the entire publication!

Scher, I.S., Stepan, L.L. & Hoover, R.W. Head and neck injury potential during water sports falls: examining the effects of helmets. Sports Eng 23, 7 (2020). https://doi.org/10.1007/s12283-020-0321-6

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18. Staffordshire Conference on Clinical Biomechanics

Due to the ongoing situation, the 18th Staffordshire Conference on Clinical Biomechanics was held online on 1st & 2nd May 2020. The positive thing about it (besides the round-the-clock coffee supply of course): The participation fee was reduced to 25€ for everyone and the recorded videos will be available online here for another 24 months.

The topics discussed over the two days were wide-ranging, ranging from footwear, prosthetics, orthotics and general clinical applications of technology, sports and clinical populations to the mechanics of tissues.

The main speakers at the conference were:

• Sharon Dixon (University of Exeter) – Using biomechanical analysis to support military and elite sporting populations
• Paul O Malley (Profeet) – The performance enhancing effect of running footwear: Evolution or Revolution?
• Professor Hazel Screen (Queen Mary University of London) – Achilles tendon – Engineering approaches to exploring injury
• Professor Costis Maganaris (Liverpool John Moores University) – Joint & Muscle-Tendon Mechanics in Children with Cerebral Palsy
• Dr Anita Williams (University of Salford) – Perceptions of the role of footwear – identity versus foot health?
• Nina Davies (Leeds Community Healthcare NHS Trust) – Gait deviations in young children – what raises concern?
• Michael Rexing (Human Study AV.) – Efficient walking in neuromuscular lower limb orthotics through kinetic energy conversion
• Dr Andy Franklyn-Miller (SSC Sports Medicine) – Controversies in biomechanically driven gait reeducation for lower limb injury
• Tom Kepple (C-Motion, Inc.) and Steven Cadavid (Kinatrax, Inc.) – Markerless Motion Capture for in Game Baseball Biomechanics Analysis
• Dr Alfred Gatt (University of Malta) – Pressure and temperature mapping in diabetic foot disease

However, a total of 27 presentations were held, all of which are certainly worth seeing! These were watched live by the 364 deligates from 28 different countries around the world.