Head Impact Telemetry in Contact Sports

Head Impact Telemetry in Contact Sports

Module Overview

  • This lecture is part of a module covering various topics:
    • Head Impact Telemetry
    • Sex Differences
    • Workplace Injuries
    • Neurological Control of Movement

Lecture Objectives

  • Feedback for Lab 1 Test
  • Recap of Lecture 5: Brain Injury Biomechanics
  • Framework for minimizing the risk of brain injuries in sport
  • Understanding head impact telemetry
  • Summary of existing head impact literature
  • Soft tissue artifact and common problems
  • Importance of accurate head impact measurement
  • Recent findings in male vs female head impact
  • Medico-Legal Aspects: Clinical Negligence
  • 2024 World Rugby Instrumented Mouthguard Mandate & Current World Rugby – SU study

Recap: Head Impacts in Sport

  • Understanding the sports concussion problem.
  • Repetitive head trauma in collision sports linked with acute and chronic brain injuries.
  • Do we know enough to know how much we don’t know?
  • How to measure impacts to the head.
  • Different measurement methods for head impact data.
  • Different severity metrics.
  • What is important to measure?
  • Individual differences.

The Problem of Concussions and Head Impacts

  • Increasing concern over concussion injuries and repetitive head impacts in rugby union.
    • Short and long-term brain injury potential.
  • NFL $1.35 billion clinical negligence lawsuit in 2016.
  • Concern over rugby, with some lawsuits in motion.
  • Concussion = 25% of all match injuries in English Premiership men’s rugby.
  • Serious brain injuries and some fatalities reported in rugby in all grades.
  • Repetitive head trauma in collision sports linked with acute and chronic brain injuries.
  • On average, a professional rugby union player is more likely than not to sustain a concussion after 25 matches

The Brain Injury Issue in Collision Sports

  • New articles are published daily on the topic
  • Between 2013 and 2017, 11 rugby union or rugby league players - aged 14 to 21 - had died after head injuries.
  • England's Rugby Football Union is committed to improving player safety.
  • 47% of all match injuries are associated with the tackle and that concussion accounted for 19% of all injuries to the ball carrier and 43% of all injuries to the tackler.
  • Lowering the height of the tackle will benefit both the ball carrier and the tackler.

Framework to Minimise Risk

  • Concussive injuries are a problem in collision sports.
  • Utilize head impact telemetry and video to quantify impacts.
  • Understand when/where/how the biggest magnitude head impacts are happening.
  • Trial modified movement strategies using quantitative measurement methods.

Why Measure Head Impacts?

  • An integrated neurobiopsychosocial model of mTBI is yet to be achieved.
  • Future studies will investigate the correlation between multi-dimensional predictor and outcome variables associated with mTBI from a fully neurobiopsychosocial perspective.
  • Will also enable a longitudinal perspective on factors that influence both short-range and long-term outcomes after sport related concussion.
  • Large, prospective studies are required to more definitively determine the short-term and long- range influence of head impact exposure on the health of athletes who compete in contact and collision sports at all competitive levels.

What is Head Impact Telemetry?

  • Methods of quantifying inertial loading of the head.
  • 1961: Medical committee raised concern with incidence of head injuries in American football, suggested gathering head impact data.
  • 1963-1975: Instrumented suspension helmets developed and refined, used to measure individual athletes.
  • 1983: Morrison (PhD thesis, Penn State Uni): instrumented helmets for American Football. Unreasonably high peak acceleration values recorded >500g.
  • Early systems focused on linear acceleration of the head, most modern systems measure 3-axis linear acceleration and 3-axis rotational velocity (from which rotational acceleration is derived).
  • Must ensure that the sensors are actually measuring what the SKULL is doing.
  • A lot of helmet, skin patch and head band systems don’t achieve secure sensor-skull coupling, giving inaccurate data.
  • tele, "remote", and metron, "measure"

Key Aspects of Head Impact Telemetry

  • New data now available measuring number, frequency, magnitude and impact dynamics in contact sports – training or competition and includes females.
  • Valid head impact telemetry methodology on sports field difficult to achieve. Focus is helmeted sports.
  • Now accepted: Brain injuries result from a combination of linear and rotational acceleration, impact duration, impact location and direction.
  • Head impact telemetry began in 1960s. Early head impact telemetry metrics used only linear head acceleration.
  • Human brain injury threshold knowledge was based upon impacts to cadavers and animal models (single impact focus).
  • Traumatic brain injuries (TBI): rapid acceleration of, or impact to the head.
  • Hundreds of scientific publications (single impact focus, less on cumulative, repetitive impacts).

Modern Head Impact Telemetry Systems

  • Instrumented Mouthguards (iMG)
    • Very good coupling IF fitted properly to the teeth with no vibrations, securely coupled to upper teeth.
  • Head Patches
    • Poor coupling, can lead to erroneous data, under and over-predicting head impact magnitudes
  • Headbands
    • Poor coupling to the skull, can move with skin and a lot more with long hair, which carries weight and momentum
  • Helmet Sensors
    • Most of early work in this area is based on helmet sensors, which are poorly coupled to the skull, highly erroneous data, including helmets flying off heads.

Helmet Sensors (NFL)

  • Helmets translated 12- 41 mm & rotated 37 deg more than the head
  • Peak linear acceleration of the helmet = 2-5 times higher than head
  • Peak angular velocity of helmet = 37% less - 71% more than head
  • This system has been used to collect hundreds of thousands of impacts in American Football, Ice Hockey and Lacrosse
  • The results from these studies have been used to derive head impact severity metrics which are used to predict brain injury
  • We need new metrics derived from valid, reliable systems to progress this field

Skin Patches

  • Placed on skin, 1000 Hz, Very sensitive to STA
  • Skin patch over-predicted by 15±715 \pm 7 g and 2500±12002500 \pm 1200 rads/s2s^2
  • Skull cap over-predicted by 50±3150 \pm 31 g and 4300±27004300 \pm 2700 rads/s2s^2
  • Initial head impact studies for rugby union, league and Aussie rules used skin patches – those results now known to be invalid, but still out there
  • A number of assumptions in software
  • Head centre of mass calculated based on 50th percentile human norm (male)
  • Impact direction displayed on app – dependent on accuracy of sensor placement and STA
  • Need to state on app which side of the head for CoM reconstruction

Why is Accuracy Important?

  • Previous head impact telemetry research in rugby and related sports has generated unexpectedly high head acceleration values: … and high numbers of head impacts per match, for example 95±133 in club-level rugby union (1)
  • MUST HAVE tight sensor-skull coupling to record accurate skull acceleration values. This can be achieved with custom-fit mouthguards

Instrumented Mouthguards (iMGs)

  • Demonstrated the best sensor-skull coupling of all head impact systems IF care is taken to custom-fit to individual’s teeth
  • Quite a few brands now available on the market, some have validation research behind them and some do not
  • Studies published with early developments of iMGs have yielded inaccurate data (like 200 g), but these were large, heavy and not custom-fit to teeth
  • World Rugby now mandate the use of iMGs in 6 Nations and other international competitions
  • Increasing numbers of papers published using iMGs to improve safety of rugby and other contact sports
  • See papers in this lecture folder by Tooby et al., Williams et al., Woodward et al., for how iMG data is being used to refine rules and training practices in various rugby populations

2024 World Rugby Mandate of iMGs

  • January 2024, World Rugby investing $2.4 million to facilitate the adoption of these worldwide
  • Four current WR-funded studies for women’s rugby using these (RFU, Swansea, Calgary and Ireland)
  • “It's a game changer for our sport — it's bringing tech into the space where it never has been,” World Rugby chief medical officer Éanna Falvey said, noting the overarching mission is to track each athlete’s overall impact load. “The focus of this is about individualizing care.”

Instrumented Mouthguards in Use

  • In a rugby first, a player was taken off for an HIA after an alert that was triggered by a mouthguard
  • 6 Nations 2024 and 2025

Sex Differences in Head Impact Magnitude & Mechanisms (iMG Data)

  • 145 male and 73 female impacts were video-verified
  • Sex differences in impact magnitude did not significantly differ
  • Median Peak linear acceleration (PLA)
    • Male = 12.5 g (IQR 7.0)
    • Female = 11.7 g (IQR 7.0)
  • Median Peak Rotational Acceleration (PRA)
    • Male = 849.4 rad·s−2s^{-2} (IQR 479.8)
    • Female = 800.2 rad·s−2s^{-2} (IQR 677.7)

Head Impact Mechanisms

  • Categorization of head impact types (Direct contact with a hard body part, Direct contact with a soft body part, Direct contact with the ground, Indirect)

'Impact' of our Impact Studies

  • The activities have been identified as important in mitigating against injury and they are especially important in
    the women's game where the injury mechanisms for concussion are different to the men's game (more head to
    ground and uncontrolled whiplash impacts) and rates are higher. On average, evidence suggests neck strength in
    female rugby players is 47% lower than in males

Swansea University Head Impact Research

  • Multiple links to articles related to the research

Head Impact Reduction in Women’s Rugby

  • Integrated Analytics: Head impact kinematics, Neck strength, Bespoke neurocog function tests, Anthro- pometric testing, Injury reporting, Video Analysis, Menstrual cycle monitoring

Machine Learning for Women's Rugby Head Impacts

  • David Powell -Swansea University PhD Candidate

Technology, reliability and controversy

  • What does the sensor data mean for the individual?
  • What is meant by an ‘impact threshold’?
  • Valid sensor technologies continue to offer objective data that have been used to improve player safety and reduce injury risk

Medicolegal Aspects

  • Insurance companies
    • Only one now covers neurological injury for NFL, NCAA and Pop Warner American Football
    • Rugby not yet at this stage but not a great situation
  • Clinical negligence lawsuits
    • $1.6 b NFL (2015)
    • Killian Willis
    • Jamie Cudmore
  • Forensic Science Principles
    • the application of scientific methods and techniques to matters under investigation by a court of law
    • *Head impact telemetry data in contact sports must therefore comply with strict forensic science standards to be used in legal proceedings
    • These standards extend to management and governance of data collected from athletes

Summary

  • The field of head impact telemetry in sports is still evolving
  • Many scientific papers report erroneous data – big problem internationally
  • Need to introduce strict criteria for recording and reporting of head impact data
  • Generate comparable studies, with minimum standards for coupling, filtering, recording speed
  • Then we can work on developing threshold criteria and improving understanding of what head impact telemetry data means - firstly for individuals, then more generally over time