The influence of repeated chin bar impacts on the protective properties of full-face mountain biking helmets

Abstract

Full-face helmets are designed to protect against head and face injuries during downhill and free-ride mountain biking. This study assessed whether multiple impacts and helmet type are related to the protective properties of full-face helmets. A drop tower fitted with a helmeted headform simulated impacts to the chin following a forwards fall. Four models of full-face mountain biking helmets were tested. Three repeated trials were completed for each helmet at four impact velocities. Outcome variables included head injury criterion score, peak force, and peak acceleration. Peak accelerations for all trials were below the 300 g pass/fail criterion used in some testing standards. Multiple impacts reduced helmet protective properties, most noticeably at the higher impact velocities (increases in impact severity measures ranging from 11% to 22% for low and 17% to 49% for higher impact velocities). However, the effects of multiple impacts were smaller than the differences observed across individual helmet types. Helmet protective properties were associated with local chin bar characteristics, most notably chin bar length at higher impact velocities. Towards the goal of reducing overall head/brain injury risk in cyclists, there may be value in complimentary messaging about the importance of repeated impacts and helmet type on the protective properties of downhill mountain biking helmets.

Keywords

Repeated impacts helmet standards downhill mountain biking head injury criterion skull fracture traumatic brain injury helmet characteristics chin bar

Get full access to this article

View all access options for this article.

References

Carmont

. Mountain biking injuries: a review. Brit Med Bull 2008; 85: 101–112.

Chow

Kronisch

. Mechanisms of injury in competitive off-road bicycling. Wilderness Environ Med 2002; 13: 27–30.

Chow

Bracker

Patrick

. Acute injuries from mountain biking. West J Med 1993; 159: 145–148.

Nelson

McKenzie

. Mountain biking-related injuries treated in emergency departments in the United States, 1994–2007. Am J Sports Med 2011; 39: 404–409.

Kim

Jangra

Ritchie

. Mountain biking injuries requiring trauma centre admission: a 10-year regional trauma system experience. J Trauma 2006; 60: 312–318.

Ashwell

McKay

Brubacher

. The epidemiology of mountain bike park injuries at the Whistler Bike Park, British Columbia (BC), Canada. Wilderness Environ Med 2012; 23: 140–145.

Chang

. Head injury in facial impact – a finite element analysis of helmet chin-bar performance. J Biomech Eng 2000; 122: 640–646.

McDermott

Lane

Brazenor

. The effectiveness of bicyclist helmets: a study of 1710 casualties. J Trauma 1993; 34: 834–845.

Attewell

Glase

McFadden

. Bicycle helmet efficacy: a meta-analysis. Accid Anal Prev 2001; 33: 345–352.

10.

Elvik

. Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy: a re-analysis of Attewell, Glase and McFadden, 2001. Accident Anal Prev 2011; 43: 1245–1251.

11.

Social Trail Riders Online Forum. Life of full face helmets, http://www.socaltrailriders.org/forum/showthread.php?t=37862&s=bf23868092de5dc55d1074497f829e95#top (2009, accessed 16 February 2015).

12.

Classic Mountain Bike Forums. Head wreck, replace helmet?http://forums.mtbr.com/downhill-freeride/had-wreck-replace-helmet-682675.html (2011, accessed 16 February 2015).

13.

Classic Mountain Bike Forums. Should you replace a helmet after it’s been dropped?http://forums.mtbr.com/apparel-protection/should-you-replace-helmet-after-its-been-dropped-120655.html (2005, accessed 16 February 2015).

14.

Bouix

Viot

Lataillade

. Polypropylene foam behaviour under dynamic loadings: strain-rate, density and microstructure effects. Int J Impact Eng 2009; 36: 329–342.

15.

Lee

Park

Yoon

. Dynamic mechanical characteristics of expanded polypropylene foams. J Cell Plast 2010; 46: 43–55.

16.

Mills

Hwang

AMH

. The multiple-impact performance of high-density polyethylene foam. Cell Polym 1989; 8: 259–276.

17.

POC Sports. Cortex Flow, http://www.pocsports.com/en/product/2131/cortex-flow (n.d., accessed January 2014).

18.

Consumer Product Safety Commission (CPSC). Which helmet for which activity?http://www.helmets.org/cpscpam.pdf (n.d., accessed January 2014).

19.

Schwartz

. Should bike helmet rules change to match concussion research?CBC News, 2July2013, http://www.cbc.ca/news/health/story/2013/07/02/f-bicycle-helmet-concussion.html?cmp=rss (accessed 30 January 2014).

20.

Canadian Standards Association CAN/CSA-D113.2-M89:2009. Cycling helmets.

21.

CPSC 16 CFR Part 1203:2012. Safety standard for bicycle helmets: final rule.

22.

Snell Memorial Foundation B95:1995. Standard for protective headgear.

23.

ASTM Standard F1952:2010. Standard specification for helmets used in downhill mountain bicycle racing.

24.

ASTM Standard F1446:2012. Standard test methods for equipment and procedures used in evaluating the performance characteristics of protective headgear.

25.

Snell Memorial Foundation M2015:2015. Standard for protective headgear: for use with motorcycles and other motorized equipment.

26.

UN ECE 22.04:2002. Uniform provisions concerning the approval of protective helmets and their visors for drivers and passengers of motor cycles and mopeds.

27.

Euro New Car Assessment Program (NCAP). Euro NCAP – for safer cars crash test safety rating, http://www.euroncap.com/home.aspx (2015, accessed February 2015).

28.

Rowson

Duma

. Development of the STAR evaluation system for football helmets: integrating player head impact exposure and risk of concussion. Ann Biomed Eng 2011; 39: 2130–2140.

29.

Government of the United Kingdom. SHARP – the helmet safety scheme, http://sharp.direct.gov.uk/ (2013, accessed January 2014).

30.

NOCSAE ND002-13m13:2013. Standard performance specification for newly manufactured football helmets.

31.

NOCSAE ND030-11m12:2012. Standard performance specification for newly manufactured hockey helmets.

32.

Rowson

Duma

. Hockey STAR: a methodology for assessing the biomechanical performance of hockey helmets. Ann Biomed Eng. Epub ahead of print 30 March 2015. DOI: 10.1007/s10439-015-1278-7.

33.

Bell. Bell sanction helmet, https://www.bellhelmets.com/en_ap/cycling/helmets/sanction/ (2013, accessed 12 June 2013).

34.

Bell. Bell drop mountain bicycle helmet, http://www.thebellstore.com/Other/bellbicycle/Drop.html (2013, accessed 12 June 2013).

35.

Giro. Giro remedy, http://www.giro.com/ca_en/products/men/helmets/remedy.html/ (2013, accessed 12 June 2013).

36.

ASTM Standard F1292-04:2004. Standard specification for impact attenuation of surfacing materials within the use zone of playground equipment.

37.

NOCSAE Document 001-08m08b:2009. Standard test method and equipment used in evaluating the performance characteristics of protective headgear/equipment.

38.

Dixon

Brodie

IKR

. The new ISO standard for ice hockey helmets and face protectors: moving towards international standards harmonization and conformity assessment. In: Castaldi

Bishop

Hoerner

(eds) Safety in ice hockey: second volume, STP1212. Philadelphia, PA: ASTM, 1993, pp.192–213.

39.

Cripton

Dressler

Stuart

. Bicycle helmets are highly effective at preventing head injury during head impact: head-form accelerations and injury criteria for helmeted and unhelmeted impacts. Accid Anal Prev 2014; 70: 1–7.

40.

Syed

Willing

Jenkyn

. Video analysis of the biomechanics of a bicycle accident resulting in significant facial fractures. J Craniofac Surg 2013; 24: 2023–2029.

41.

Forbes

Awad

Zuckerman

. Association between biomechanical parameters and concussion in helmeted collisions in American football: a review of the literature. Neurosurg Focus 2012; 33: E10.

42.

Zhang

Yang

King

. A proposed injury threshold for mild traumatic brain injury. J Biomech Eng 2004; 126: 226–236.

43.

Prasad

Mertz

. The position of the United States delegation to the ISO working group 6 on the use of HIC in the automotive environment. SAE paper 851246, 1985.

44.

Craig

Bir

Viano

. Biomechanical response of the human mandible to impacts of the chin. J Biomech 2008; 41: 2972–2980.

45.

Schneider

Nahum

. Impact studies of facial bones and skull. SAE paper 720965, 1972.

46.

Cormier

Manoogian

Bisplinghoff

. The tolerance of the maxilla to blunt impact. J Biomech Eng 2011; 133: 064501.

47.

Cormier

Manoogian

Bisplinghoff

. The tolerance of the nasal bone to blunt impact. Ann Adv Automot Med 2010; 54: 3–14.

48.

Transport for NSW. CRASH – Consumer Rating and Assessment of Safety Helmets, http://www.crash.org.au/ (2015, accessed May 2015).

49.

King

. Comments on Rowson and Duma (2011). Ann Biomed Eng 2012; 40: 2510–2511.

50.

Rowson

Duma

. The Virginia Tech Response. Ann Biomed Eng 2012; 40: 2512–2518.

51.

Jadischke

Viano

Dau

. On the accuracy of the Head Impact Telemetry (HIT) System used in football helmets. J Biomech 2013; 46: 2310–2315.

52.

Duma

Rowson

. Re: on the accuracy of the Head Impact Telemetry (HIT) System used in football helmets. J Biomech 2014; 47: 1557–1558.

53.

Jadischke

McCarthy

. Response to the letter to the editor ‘Re: on the accuracy of the Head Impact Telemetry (HIT) System used in football helmets’. J Biomech 2014; 47: 1558–1563.

54.

National Operating Committee for Standards on Athletic Equipment (NOCSAE). Rating system cannot predict helmets’ ability to prevent concussions, http://nocsae.org/wp-content/uploads/2014/05/NOCSAE-Release-on-2014-Va-Tech-Ratings-FINAL-5-27-14.pdf (2014, accessed 13 August 2015).

55.

Rowson

Duma

Greenwald

. Can helmet design reduce the risk of concussion in football? Technical note. J Neurosurg 2014; 120: 919–922.

56.

Hardy

Mason

Foster

. A study of the response of the human cadaver head to impact. Stapp Car Crash J 2007; 51: 17–80.

57.

Lloyd

Nightingale

Song

. Impact properties of adult and ATD heads. In: Proceedings of the IRCOBI 2012 conference, Dublin, 12–14 September 2012, paper no. IRC-12-64.