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Can we use wearable microtechnology devices to monitor motor changes post-concussion in team sport players?
Dunne, Laura
Dunne, Laura
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Abstract
Sports-related concussions (SRCs) are common amongst athletes partaking in both contact (e.g., tackle) and non-contact (e.g., struck by ball) sports. Incidence of SRC has seen a steady increase amongst athletes, with proposed reasons including increased physicality, improved diagnostic tests, and increased awareness surrounding concussion and future complications of un-reported cases.
Concussion, otherwise referred to as mild traumatic brain injury (mTBI) is described as a transient disturbance of brain function due to direct (e.g., head contact) or indirect (e.g., whiplash) mechanisms. Due to the biomechanical properties of the brain, it has an increased susceptibility to injury under rotational accelerations typically associated with indirect impacts to the head. Symptoms following injury include headache, nausea, behavioural abnormalities (e.g., mood changes), vision and coordination deficits.
Current management of SRC is heavily reliant on subjective assessment tools, such as the Sports Concussion Assessment Tool (SCAT6) and, the recently introduced, office-based assessment (SCOAT6). These assessments are multidimensional to account for the wide variety of symptoms that may be experienced by individuals. They are used to assist with both diagnosis and return to play (RTP) clearance. Of particular interest is the assessment of motor function. The Balance Error Scoring System (BESS), it’s modified version (mBESS), and tandem gait tasks are commonly used to assess motor performance, ultimately informing clearance for RTP. Of concern is the use of such tools, initially designed to assist with diagnosis, to evaluate RTP readiness. It is proposed that these assessments may lack the resolution or sensitivity to detect potential changes in motor function due to their simplicity and subjective nature. Given that there appears to be an increased risk of subsequent concussion and musculoskeletal injury upon RTP following SRC, players may be returning with lingering, subclinical deficits in function that go undetected by clinical tests. Laboratory assessments, such as 3D motion analysis or pressure sensitive walkways, may provide detailed insight into the deficits seen post-concussion; however, they are difficult to implement for most practitioners.
The aim of this thesis was to establish a more comprehensive motor assessment to further complement the current clinical assessments implemented as part of concussion management protocols. (1) Consolidate the reliability and validity of motor function assessments currently used in concussion management and further summarise their feasibility for clinicians and other end-users. (2) Assess the reliability of ankle, lumbar, and thoracic mounted devices to measure gait parameters on grassed surfaces. (3) Determine if lumbar- and thoracic-mounted IMUs can detect changes in movement strategies amongst athletes returning to play following a diagnosed SRC across a range of movement velocities. The findings from the systematic review identified limitations with currently implemented motor assessments; notably poor sensitivity of these assessments beyond the acute stages of concussion (>7 days). Most motor assessments rely heavily on subjective interpretation (e.g. number of errors) or blunt objective measures (e.g. time to complete task). They do not allow practitioners to understand what may be happening at a neuromuscular level to implement targeted rehabilitation strategies. The systematic review concluded that static and dynamic balance assessments may lack the requisite sensitivity to detect underlying neuromuscular changes in motor performance, especially when performed beyond acute stages. Gait-based assessments (single- and dual-task) were better at distinguishing between concussed and healthy populations, with instrumented versions being superior. Laboratory assessments are valid and reliable and are excellent instruments to obtain objective measures within a research setting. However, the accessibility, associated costs, and controlled environments mean they cannot be used by practitioners to monitor athletes returning to play. Thoracic worn IMUs are currently utilised by many team sport athletes to monitor training and game-play loads. The portability and low-cost of these devices make them suitable for team sport athletes to use within any desired environment. These devices have been shown to be effective at differentiating athletes suffering neuromuscular fatigue and it was hypothesised that this use may also be extended to monitoring the movement changes that present post-concussion.
To establish if IMUs can be used in the field to assist with concussion management, this thesis first sought to determine the test-retest reliability of ankle-, lumbar-, and thoracic-mounted IMUs to measure commonly reported linear and non-linear gait variables across set- and self-paced activities of increasing velocities performed on grassed surfaces. These IMU locations have previously demonstrated acceptable reliability for a range of outcome measures. However, these have only been performed within controlled, stable environments (e.g. running track, indoors). Access to these environments may be limited for many team sport athletes, therefore determining the reliability of these device locations on grassed surfaces was warranted.
Our findings showed that ankle-, lumbar-, and thoracic-mounted IMUs, in general, displayed acceptable test-retest reliability for a range of linear and non-linear gait variables. These results were consistent across velocities (walk, jog, run) and pace conditions (set- and self-paced). These findings support the use of IMUs to monitor common gait variables within the field, increasing feasibility for practitioners. Nonetheless, limitations for ankle- and lumbar-mounted IMUs do exist. Notably, these locations may impede activities performed in training and game environments (e.g. tackling, kicking a ball). Thoracic-mounted IMUs housed in a tight-fitted vest are already utilised by many team sport athletes and are less affected by sport-specific requirements, making them suitable for most athletes and sports. Practitioners can be confident that thoracic-mounted IMUs can reliably measure variables of gait over a five-week period based on the current research.
Upon establishing the test-retest reliability of ankle-, lumbar-, and thoracic-mounted IMUs, this thesis sought to determine whether there were differences in gait derived from the lumbar- and thoracic-mounted IMUs between concussed and control athletes at a range of movement velocities. To date, post-concussion gait assessments have been isolated to walking tasks which may not accurately represent the demands required upon return to play. Therefore, we aimed to investigate if increasing velocities (jog and run) also displayed between-group differences and assess whether they existed beyond RTP clearance.
Our findings suggest that variations in gait strategies still exist beyond RTP timelines. These variations were evident across linear and non-linear outcome measures collected via lumbar- and thoracic-mounted IMUs. Previous literature has suggested concussed athletes have a slower gait when walking. Whilst our findings supported this, concussed athletes performed jog and run activities at faster speeds than healthy controls. Largest between-group differences were seen for measures of sample entropy (vertical and mediolateral acceleration), mediolateral acceleration profiles, and centre of mass (COM) displacement.
Concussed athletes demonstrated greater mediolateral movement, indicating more side-to-side movement, and reduced COM displacement and vertical acceleration, suggesting reduced lower-limb stiffness. Non-linear analysis showed greater irregularity for vertical accelerations across all activities for concussed athletes, indicating a less predictable movement pattern for these participants. In general, this score improved for walk and run activities, with no change seen for jogging.
Differences between device locations were particularly evident for the assessment of sample entropy and mediolateral acceleration. Data obtained from the thoracic-mounted IMUs suggest greater variability in mediolateral acceleration, while the lumbar-mounted IMUs only showed greater irregularity for walk activities. Due to being further up the kinetic chain, thoracic-mounted IMUs may be more influenced by upper-limb and trunk movements, whereas measures from lumbar-mounted IMUs may better represent lumbo-pelvic movements and COM displacement. Both sites can provide valuable information, but practitioners must be aware of the limitations or bias (e.g. magnitude of some outcome variables) associated with each location when interpreting results. Notably, lumbar-mounted devices are not commonly worn and therefore require the attachment of an additional device. Thoracic mounted devices are commonly worn during team sport training and competition and may allow for pre-injury measures and regular post-injury measures of gait to be performed with relative ease to aid decision making in team sport.
In conclusion, the studies within this thesis found that ankle-, lumbar-, and thoracic-mounted IMUs can reliably measure a range of linear and non-linear gait metrics during activities across a range of velocities when performed on grassed surfaces. In addition, lumbar- and thoracic-mounted IMUs can be used to show differences between concussed and healthy athletes for various linear and non-linear outcome measures up to 50-days post-concussion.
These findings support the use of IMUs in the field to provide a more comprehensive assessment of gait following concussion. The low-cost and portability of IMUs make them easy for many team sport athletes and practitioners to access and use to assess any potential changes in gait strategies following injury. Use of instrumented gait assessments across increasing velocities may provide important insight to inform an athlete’s RTP readiness when compared with more traditional clinical assessments (e.g. BESS) and may inform practitioners of additional assessment requirements to ensure player safety and well-being following RTP.
Keywords
sports-related concussion, wearable technology, inertial measurement unit, motor strategies
Date
2025
Type
Thesis
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Page Range
1-257
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ACU Department
National School of Behavioural and Health Sciences
Faculty of Health Sciences
Faculty of Health Sciences
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Open access
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CC BY-NC-ND 4.0 (Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International)
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This work © 2025 by Laura Dunne is licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
(https://creativecommons.org/licenses/by-nc-nd/4.0).