The Influence of Concussion History and Head Acceleration on Lower Extremity Function

Sport-related concussions (SRCs) play a very debilitative role in athletics with between 1.7 – 3 million SRCs occurring annually (Clay et al., 2013; Zuckerman et al., 2015). This equates to upwards of 21.5 SRCs per 1000 athletic exposures. Research pertaining to SRC has received intense focus because of the substantial financial impact on the US healthcare system as well as the negative impact that SRCs have on the quality of life of athletes. Much of the research concerning SRC has been centered around management and ensuring adequate recovery from SRC-related symptoms. The current return to play (RTP) criteria from an SRC involves a battery of clinical tests increasing in cognitive and exercise intensity. Athletes typically pass standard RTP criteria and can resume their sport within 1-3 weeks post-SRC. However, recent literature has found that even after being cleared to RTP, long-term cognitive, neuromuscular, and motor impairments may persist. Furthermore, literature examining injury rates has shown that athletes that have a history of SRC are up to 3.7 times more likely to sustain a musculoskeletal injury upon their return to sport compared to athletes who have not suffered an SRC (Brooks et al., 2016; Cross et al., 2016; Herman et al., 2017 Lynall et al., 2015; McPherson et al., 2019; Pietrosimone et al., 2015). While there may be a direct link between the cognitive, neuromuscular, and motor control deficits and injury risk in the SRC population, the research to support this phenomenon is currently inconclusive and unable to establish a causal relationship. Prior to expanding upon the current SRC literature, it is important for readers to have a full understanding of SRC, current RTP guidelines, and the possible shortcomings in these guidelines that can place athletes with SRC history at elevated injury risk. A literature review (Chapter 1) precedes reporting of the successive experiments that were undertaken to more fully understand lower extremity function pertaining to SRC history and injury risk. The overall purpose of this dissertation was to assess the influence of SRC as well as SRC-related mechanisms on lower extremity function during landing tasks. It has been suggested in the literature that athletes with a history of SRC perform high-impact tasks (e.g., jump-landing, jump-cutting) with decreased lower extremity (LE) neuromuscular control compared to control athletes thus increasing injury risk. Further research to support this statement and its applicability with different sports populations is warranted. Current literature comparing LE landing mechanics between SRC and control athletes have neglected to examine the influence of sex as well as limb symmetry during landing. Thus, our first two studies (Chapters 2 and 3) examine the influence of sex on LE mechanics and limb symmetry between athletes with and without a history of SRC. The first study (Chapter 2) assesses the influence of sex on lower extremity limb symmetry in athletes with and without a history of SRC. The second study (Chapter 3) assesses the influence of sex on LE biomechanics in athletes with and without a history of SRC. Both experiments utilized a cross sectional study design and implement identical experimental methods. Athletes from various sports with a history of SRC were recruited for these studies and comprised the SRC group. The healthy control group was comprised of athletes without a history of SRC and were matched by age, sex, and sport. Two-way ANOVAs (α =0.05) were conducted in each study comparing sex and concussion history on selected lower extremity biomechanics parameters that have been previously associated with LE injury risk. For the first study a symmetry index was computed to compare these LE biomechanics between limbs. It was determined that female athletes with a history of SRC had significantly greater limb symmetry in vertical ground reaction force than female athletes in the control group potentially placing them at the greatest risk for LE injury. For the second study, peak discrete biomechanical parameters during landing were obtained and comparisons were made between SRC and control groups. Results showed that males in the SRC group landed with a lesser knee flexion angle than males in the control group, thus placing them at greater risk for LE injury. The third study (Chapter 4) utilized a cross-sectional design on a population of healthy individuals. The purpose of the third study was to compare different directions of induced head acceleration on LE mechanics during landing. One group of individuals was assigned to do a continuous lateral hopping task while the other group was assigned to do a continuous vertical hopping task. Both groups performed a landing task before and after their assigned hopping intervention. Comparisons were made within each group pre- and post-intervention as well as between groups. The group that performed the continuous vertical hopping task exhibited greater vertical head acceleration during the hopping task compared to the lateral hopping task group. Along with greater head acceleration during the hopping intervention, the vertical hopping task group also demonstrated greater knee abduction during landing post-intervention compared to the lateral hopping group. This suggests the utility in assessing head acceleration and its influence on landing mechanics. In summary, this dissertation consisted of three progressive studies to contribute to the understanding of the mechanisms behind the ongoing issue of athletes with a history of SRC demonstrating high impact landing strategies conducive to increased LE injury risk. The findings of our studies suggest that SRC history as well as induced head acceleration can have an impact on LE landing mechanics. A major limitation of these studies is their cross-sectional nature. This study design limits the conclusions drawn from our first two studies since it cannot be ascertained whether the mechanics observed occurred prior to the SRC being suffered. While our third study was not conducted on a population of athletes with a history of SRC, the cross-sectional design limits the conclusions that can be drawn. Future studies should adopt a study design that allows the investigator to examine the influence of SRC history and/or SRC mechanisms before and after an SRC has been sustained

Institutional change for improving accessibility in the design and delivery of distance learning – the role of faculty accessibility specialists at The Open University

The Open University (OU) has an established infrastructure for supporting disabled students. Historically, the thrust of this has focused on providing accessible adjustments post-production. In 2012, the OU implemented securing greater accessibility (SeGA) to raise awareness and bring about an institutional change to curriculum design so that the needs of all students, including disabled students, are taken into account from the outset of module design and production. A core component of SeGA is the introduction of faculty accessibility specialists (AS). This case study discusses the successes and challenges for AS in motivating and supporting production teams in the adoption of inclusive anticipatory practices to make new curriculum accessible. It also outlines the process of reasonable adjustment during presentation. It shows how collaborative working between AS has helped standardise design and production processes for accessibility, principles with wider relevance for supporting disabled students in other higher educatio

The Relationship Between Concussion History and Sex on Lower Extremity Biomechanics During a Cutting Task

Athletes with a history of sports related concussion (SRC) have been shown to exhibit lower extremity (LE) mechanics during high impact landing tasks that are conducive to increased injury risk. The underlying cause, and extent of this phenomena is currently unknown. PURPOSE: The purpose of this study was to analyze the relationship between SRC history and sex on LE biomechanics during a land-and-cut task. METHODS: College athletes with a history of SRC and a control group of healthy athletes matched by sport, position, sex, and age were recruited for this study. Both groups were comprised of 9 males and 11 females. Athletes performed an unanticipated land-and-cut task. The task consisted of each athlete standing on a 60 cm box with a visual stimulus positioned three meters away from the athlete. Various colors (green, pink, blue, and red) were presented as the visual stimulus. Athletes were instructed to only respond to a green or red light. When a red or green light was shown, athletes were instructed to step off the box, land on both limbs and perform a 45-degree cutting movement to the left or right, respectively. Two separate point biserial correlations were conducted (one for each sex) correlating group (0 = control, 1 = SRC) with the following dependent variables: vertical ground reaction force (vGRF), peak knee extensor moment (pKEM), peak knee abduction moment (pKAM), peak ankle dorsiflexion angle (pDF), peak knee flexion angle (pKFA), and peak knee abduction angle (pKA). A linear regression equation was obtained for significant correlations. RESULTS: There was a significant negative moderate correlation between group and KF in males (r = -.69, p \u3c .01). There were no other significant correlations between group and LE biomechanical variables in either males or females (p \u3e .05). A linear regression analysis showed SRC history was a significant predictor of KF (KF = 63.71 – 12.43(group); R2 = .473, p = .002) CONCLUSION: Males in the SRC group were associated with lower KF. Specifically, the regression analysis indicated that males with an SRC history had a predicted 12.4 degree decrease in KF during the land-and-cut task. This suggests previously concussed males may be at increased risk for LE injury

Viral load and antibody boosting following herpes zoster diagnosis

BACKGROUND: Acute varicella zoster virus (VZV) replication in shingles is accompanied by VZV antibody boosting. It is unclear whether persisting virus shedding affects antibody levels. OBJECTIVES: To investigate the relationship between VZV viral load and antibody titres in shingles patients during six months following diagnosis and assess whether VZV antibody titre could discriminate patients with recent shingles from healthy population controls. STUDY DESIGN: A prospective study of 63 patients with active zoster. Blood samples were collected at baseline, one, three and six months to measure VZV DNA and IgG antibody titre. We compared VZV antibody titres of zoster patients and 441 controls. RESULTS: In acute zoster, viral load was highest at baseline and declined gradually over the following six months. Mean antibody titres rose fourfold, peaking at one month and remaining above baseline levels throughout the study. Antibody levels at one, three and six months after zoster were moderately correlated with baseline but not subsequent viral load. Regarding use of antibody titres to identify recent shingles, to achieve 80% sensitivity, specificity would be 23.4%, 67.7%, 64.8% and 52.6%, at baseline, visit 2, 3 and 4 respectively, whilst to achieve 80% specificity, sensitivity would be 28.3%, 66.1%, 52.6%, 38.6%, at baseline, visit 2, 3 and 4 respectively. CONCLUSIONS: Clinical VZV reactivation boosted VZV antibody levels and the level of boosting was dependent upon baseline viral replication. While antibody titres could discriminate patients with shingles 1-6 months earlier from blood donor controls, there was a large trade-off between sensitivity and specificity

Association Between Common Infections and Incident Post-Stroke Dementia:A Cohort Study Using the Clinical Practice Research Datalink

PURPOSE: To investigate the association between common infections and post-stroke dementia in a UK population-based cohort. MATERIALS AND METHODS: A total of 60,392 stroke survivors (51.2% male, median age 74.3 years, IQR 63.9-82.4 years) were identified using primary care records from the Clinical Practice Research Datalink (CPRD) linked to Hospital Episode Statistics (HES) with no history of dementia. Primary exposure was any GP-recorded infection (lower respiratory tract infection (LRTI), urinary tract infection (UTI) requiring antibiotics, skin and soft tissue infection requiring antibiotics) occurring after stroke. The primary outcome was incident all-cause dementia recorded in primary care records. In sensitivity analyses, we restricted to individuals with linked hospital records and expanded definitions to include ICD-10 coded hospital admissions. We used multivariable Cox regression to investigate the association between common infections and dementia occurring from 3 months to 5 years after stroke. RESULTS: Of 60,392 stroke survivors, 20,969 (34.7%) experienced at least one infection and overall 4512 (7.5%) developed dementia during follow-up. Early dementia (3 months to 1-year post-stroke) risk was increased in those with at least one GP-recorded infection (HR 1.44, 95% CI 1.21-1.71), with stronger associations when hospitalised infections were included (HR 1.84, 95% CI 1.58-2.14). Late dementia (1-5 years) was only associated with hospitalised, but not with GP-recorded, infections. CONCLUSION: There was evidence of an association between common infections and post-stroke dementia, strongest in the 3-12 months following stroke. Better understanding of this relationship could help inform knowledge of pathways to dementia post-stroke and targeting of preventive interventions

The Relationship Between Concussion History And Lower Extremity Biomechanics During A Land And Cut Task

In high impact landing tasks, athletes with a history of sports related concussion (SRC) have been found to demonstrate lower extremity (LE) biomechanics that are associated with elevated injury risk. However, the exact relationships between SRC history and LE biomechanics are inconclusive. PURPOSE: The purpose of this study was to investigate the relationship between SRC history and LE biomechanics during a cutting task. METHODS: A cohort of athletes with a history of SRC (n=20) and a control group of healthy athletes (n=20) were recruited for this study. The control group were matched by age, sex, and sport. Athletes performed an unanticipated land and cut task. Athletes stood on a 60 cm box and focused on a visual light positioned three meters away from them. The light displayed green, pink, blue, or red. Athletes were instructed to step off the box, land on both limbs, and perform a 45-degree cutting maneuver to left or right when they saw red or green light respectively. A point biserial correlation was conducted correlating group (0 = control, 1 = SRC) with the following dependent variables: dominant limb ground reaction force (D_GRF), dominant limb ankle dorsiflexion angle (D_DF), dominant limb knee flexion angle (D_KFA), dominant limb knee flexion moment (D_KFM), dominant limb knee abduction angle (D_KAA), and dominant limb knee abduction moment (D_KAM). A linear regression equation was obtained for any significant correlations. RESULTS: There was a small significant negative correlation between group and KFA (r = -.342, p \u3c .01). There were no other significant correlations between group and LE biomechanical variables (p \u3e .05). A linear regression analysis showed SRC history as a significant predictor of KFA (KFA = 60.24 - 6.16(group); R2 = 0.117, p = .03). CONCLUSION: The SRC group was associated with lower KFA. According to our regression analysis, athletes with an SRC history had predicted a 6.2 degree decrease in KFA compared to the control group during the land and cut task. Furthermore, approximately 12% of the variance in KFA can be explained by SRC. This suggests that previously concussed athletes may be at a higher risk for LE injury. Further research in this area is needed to confirm this relationship

Varicella and herpes zoster vaccine development: lessons learned.

INTRODUCTION: Before vaccination, varicella zoster virus (VZV), which is endemic worldwide, led to almost universal infection. This neurotropic virus persists lifelong by establishing latency in sensory ganglia, where its reactivation is controlled by VZV-specific T-cell immunity. Lifetime risk of VZV reactivation (zoster) is around 30%. Vaccine development was galvanised by the economic and societal burden of VZV, including debilitating zoster complications that largely affect older individuals. Areas covered: We describe the story of development, licensing and implementation of live attenuated vaccines against varicella and zoster. We consider the complex backdrop of VZV virology, pathogenesis and immune responses in the absence of suitable animal models and examine the changing epidemiology of VZV disease. We review the vaccines' efficacy, safety, effectiveness and coverage using evidence from trials, observational studies from large routine health datasets and clinical post-marketing surveillance studies and outline newer developments in subunit and inactivated vaccines. Expert commentary: Safe and effective, varicella and zoster vaccines have already made major inroads into reducing the burden of VZV disease globally. As these live vaccines have the potential to reactivate and cause clinical disease, developing alternatives that do not establish latency is an attractive prospect but will require better understanding of latency mechanisms

Risk of acute respiratory infection and acute cardiovascular events following acute respiratory infection among adults with increased cardiovascular risk in England between 2008 and 2018: a retrospective, population-based cohort study

BACKGROUND: Although acute respiratory infections can lead to cardiovascular complications, the effect of underlying cardiovascular risk on the incidence of acute respiratory infections and cardiovascular complications following acute respiratory infection in individuals without established cardiovascular disease is unknown. We aimed to investigate whether cardiovascular risk is associated with increased risk of acute respiratory infection and acute cardiovascular events after acute respiratory infection using 10 years of linked electronic health record (EHR) data in England. METHODS: In this retrospective, population-based cohort study we used EHRs from primary care providers registered on the Clinical Practice Research Datalink (CPRD) GOLD and Aurum databases in England. Eligible individuals were aged 40-64 years, did not have established cardiovascular disease or a chronic health condition that would make them eligible for influenza vaccination, were registered at a general practice contributing to the CPRD, and had linked Hospital Episode Statistics Admitted Patient Care data in England from Sept 1, 2008, to Aug 31, 2018. We classified cardiovascular risk on the basis of diagnosed hypertension and overall predicted cardiovascular risk, estimated by use of the QRISK2 risk-prediction tool (comparing a score of ≥10% [increased risk] with a score of <10% [low risk]). Using multivariable Poisson regression models, we calculated incidence rate ratios (IRRs) for systemic acute respiratory infection. Among individuals who had an acute respiratory infection, we used multivariable Cox regression to calculate hazard ratios (HRs) for the risk of acute cardiovascular events within 1 year of infection. FINDINGS: We identified 6 075 321 individuals aged 40-64 years with data in the CPRD and linked data in the Hospital Episode Statistics Admitted Patient Care database between Sept 1, 2008, and Aug 31, 2018. Of these individuals, 4 212 930 (including 526 480 [12·5%] with hypertension and 607 087 [14·4%] with a QRISK2 score of ≥10%) were included in the assessment of the incidence of acute respiratory infection. After adjusting for confounders (age, sex, ethnicity, socioeconomic status, body-mass index, alcohol consumption, smoking status, and consultation frequency in the hypertension analysis; and alcohol consumption and consultation frequency in the QRISK2 analysis), the incidence of acute respiratory infection was higher in individuals with hypertension than those without (IRR 1·04 [95% CI 1·03-1·05]) and higher in those with a QRISK2 score of 10% or higher than in those with a QRISK2 score of less than 10% (1·39 [1·37-1·40]). Of the 442 408 individuals who had an acute respiratory infection, 4196 (0·9%) had an acute cardiovascular event within 1 year of infection. After adjustment (for age, sex, ethnicity, socioeconomic status, body-mass index, alcohol consumption, and smoking status in the hypertension analysis; and for alcohol consumption in the QRISK2 analysis), hypertension (HR 1·98 [95% CI 1·83-2·15]) and a QRISK2 score of 10% or higher (3·65 [3·42-3·89]) were associated with a substantially increased risk of acute cardiovascular events after acute respiratory infection. INTERPRETATION: People with increased cardiovascular risk but without diagnosed cardiovascular disease, measured by diagnosed hypertension or overall predicted cardiovascular risk, could benefit from influenza and pneumococcal vaccine prioritisation to reduce their risk of both acute respiratory infection and cardiovascular complications following an acute respiratory infection. FUNDING: British Heart Foundation and the Wellcome Trust