Quantifying and Comparing the Head Impact Biomechanics of Different Player Positions for Canadian University Football

Differences between Canadian and American football could affect the magnitudes of head impacts and risk of concussion to Canadian players. This study sought to quantify and compare the number, magnitude, and location of impacts that Canadian University football players of different positions experienced during games and practice in a season. A kinematic measuring device collected the linear accelerations and rotational velocities of the head from impacts experienced by players competing in practices and games. The impact magnitudes that were experienced in games were significantly larger than in practice. The offensive back position and wide receiver position had significantly larger peak linear and rotational accelerations than the offensive linemen position. The magnitudes of impacts experienced by the wide receiver position in Canadian football were larger and not consistent with previous American studies, likely due to the pass style offence that is common in Canadian football. We observed that the head impact magnitudes vary by position, and session type in Canadian football

A Biofidelic Evaluation of The Head Impact Telemetry System on Measuring Head Impact Location and Frequency Through Laboratory and On-Field Assessments

Concussions are caused by excessive linear and rotational head accelerations from direct or indirect head loading. Researchers have used head impact sensors, like the Head Impact Telemetry (HIT) System, to measure football head impact frequency, magnitude, and location. The HIT System’s measurement accuracy has previously been compared to gold-standard reference sensors rigidly coupled to anthropometric test device (ATD) heads. The ATD heads’ skin does not mimic human skin compliance and oiliness, creating an artificial coupling surface between the ATD head and the HIT System. This dissertation’s purpose was to evaluate the HIT System’s impact detection and location accuracy while the system was coupled to more biofidelic conditions better replicating the system’s intended use on the football playing field. Using an innovative biofidelic surrogate head testing paradigm—cadaver human head drops—the HIT System measured statistically different impact location coordinates than reference sensors except at the facemask drop location (p>0.05). The HIT System had low agreement with reference sensors in measuring impact location category on most drop sites. We subsequently quantified the HIT System’s impact detection and head impact location measurement accuracy while high school football players wore the system during special teams plays in games. Video observed impacts and impact locations were documented and merged with HIT System impact data. The HIT System’s impact filtering algorithm accurately categorized 70% of the data collection trigger events as either true head impacts or non-head impacts. The HIT System agreed with video observations of impact location on 64% of 129 analyzed impacts. Head impact frequency may be underestimated for studies using the HIT System during special teams plays, and potentially other play types. We recommend confirming head impact locations with video analysis to ensure accurately quantifying the head loading environment to the extent possible. Understanding the relationships between impact location and injury risk can lead to protective equipment improvements, identifying athletes for technique improvement limiting head impact exposure and concussion risk, and developing data-derived rule modifications for reducing concussion risk.Doctor of Philosoph

Saccade and Fixation Eye Movements During Walking in People With Mild Traumatic Brain Injury

Background: Clinical and laboratory assessment of people with mild traumatic brain injury (mTBI) indicate impairments in eye movements. These tests are typically done in a static, seated position. Recently, the use of mobile eye-tracking systems has been proposed to quantify subtle deficits in eye movements and visual sampling during different tasks. However, the impact of mTBI on eye movements during functional tasks such as walking remains unknown. Objective: Evaluate differences in eye-tracking measures collected during gait between healthy controls (HC) and patients in the sub-acute stages of mTBI recovery and to determine if there are associations between eye-tracking measures and gait speed. Methods: Thirty-seven HC participants and 67individuals with mTBI were instructed to walk back and forth over 10-m, at a comfortable self-selected speed. A single 1-min trial was performed. Eye-tracking measures were recorded using a mobile eye-tracking system (head-mounted infra-red Tobbii Pro Glasses 2, 100 Hz, Tobii Technology Inc. VA, United States). Eye-tracking measures included saccadic (frequency, mean and peak velocity, duration and distance) and fixation measurements (frequency and duration). Gait was assessed using six inertial sensors (both feet, sternum, right wrist, lumbar vertebrae and the forehead) and gait velocity was selected as the primary outcome. General linear model was used to compare the groups and association between gait and eye-tracking outcomes were explored using partial correlations. Results: Individuals with mTBI showed significantly reduced saccade frequency (p = 0.016), duration (p = 0.028) and peak velocity (p = 0.032) compared to the HC group. No significant differences between groups were observed for the saccade distance, fixation measures and gait velocity (p > 0.05). A positive correlation was observed between saccade duration and gait velocity only for participants with mTBI (p = 0.025). Conclusion: Findings suggest impaired saccadic eye movement, but not fixations, during walking in individuals with mTBI. These findings have implications in real-world function including return to sport for athletes and return to duty for military service members. Future research should investigate whether or not saccade outcomes are influenced by the time after the trauma and rehabilitation

Free-living gait does not differentiate chronic mTBI patients compared to healthy controls

Background Physical function remains a crucial component of mild traumatic brain injury (mTBI) assessment and recovery. Traditional approaches to assess mTBI lack sensitivity to detect subtle deficits post-injury, which can impact a patient’s quality of life, daily function and can lead to chronic issues. Inertial measurement units (IMU) provide an opportunity for objective assessment of physical function and can be used in any environment. A single waist worn IMU has the potential to provide broad/macro quantity characteristics to estimate gait mobility, as well as more high-resolution micro spatial or temporal gait characteristics (herein, we refer to these as measures of quality). Our recent work showed that quantity measures of mobility were less sensitive than measures of turning quality when comparing the free-living physical function of chronic mTBI patients and healthy controls. However, no studies have examined whether measures of gait quality in free-living conditions can differentiate chronic mTBI patients and healthy controls. This study aimed to determine whether measures of free-living gait quality can differentiate chronic mTBI patients from controls. Methods Thirty-two patients with chronic self-reported balance symptoms after mTBI (age: 40.88 ± 11.78 years, median days post-injury: 440.68 days) and 23 healthy controls (age: 48.56 ± 22.56 years) were assessed for ~ 7 days using a single IMU at the waist on a belt. Free-living gait quality metrics were evaluated for chronic mTBI patients and controls using multi-variate analysis. Receiver operating characteristics (ROC) and Area Under the Curve (AUC) analysis were used to determine outcome sensitivity to chronic mTBI. Results Free-living gait quality metrics were not different between chronic mTBI patients and controls (all p > 0.05) whilst controlling for age and sex. ROC and AUC analysis showed stride length (0.63) was the most sensitive measure for differentiating chronic mTBI patients from controls. Conclusions Our results show that gait quality metrics determined through a free-living assessment were not significantly different between chronic mTBI patients and controls. These results suggest that measures of free-living gait quality were not impaired in our chronic mTBI patients, and/or, that the metrics chosen were not sensitive enough to detect subtle impairments in our sample