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Papers by Marshall Kendall
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2016
Brain injuries are prevalent in the sport of American football. Helmets have been used which effe... more Brain injuries are prevalent in the sport of American football. Helmets have been used which effectively have reduced the incidence of traumatic brain injury, but have had a limited effect on concussion rates. In an effort to improve the protective capacity of American football helmets, a standard has been proposed by National Operating Committee on Standards for Athletic Equipment that may better represent helmet-to-helmet impacts common to football concussions. The purpose of this research was to examine the National Operating Committee on Standards for Athletic Equipment standard and a new impact method similar to the proposed National Operating Committee on Standards for Athletic Equipment standard to examine the information these methods provide on helmet performance. Five National Operating Committee on Standards for Athletic Equipment–certified American football helmets were impacted according to the National Operating Committee on Standards for Athletic Equipment standard te...
Journal of Concussion
Head injuries in elite and youth sport have garnered growing public attention in part because of ... more Head injuries in elite and youth sport have garnered growing public attention in part because of high-profile cases of professional athletes suffering career-ending/threatening concussions and because of the increase in medical studies identifying how repeated concussive events can lead to long-term health problems, most notably degenerative brain disease. Public concerns around youth ice hockey are intensifying in light of recent evidence which suggests that effects of head injury are worse for youth than they are for athletes in later stages of life. To better understand concussion injury rate trends across all levels of youth hockey, this paper provides a retrospective analysis of concussion related hockey injury as recorded in Hockey Canada’s Injury Reporting System from the period covering 2009 to 2016, combined with two years of observational research documenting head contact events in minor hockey in the Ottawa and Gatineau regions of Ontario and Quebec. By comparing two diff...
Sports Engineering
Helmet design and development are an important tool to help mitigate the severity and frequency o... more Helmet design and development are an important tool to help mitigate the severity and frequency of head and brain injury in sport and everyday life. Helmet assessment protocols and standards often use the Hybrid III neckform as part of the impacting equipment even though it has a biased response that can affect the results. This research presents an unbiased neckform that can be used for the purposes of head impact testing that does not provide a mechanical directional bias to the impact result. A Hybrid III headform was impacted under a sporting impact protocol with a Hybrid III and an unbiased neckform. The resultant acceleration magnitudes were similar between the two necks, while larger differences (8 g and up to 4 krad/s2) were found between the acceleration components. The Hybrid III neck may have a more biased response for longer duration events (10 ms+) as this research considered only short duration impacts (5–10 ms).
Computer methods in biomechanics and biomedical engineering, 2018
Concussion in American football is a prevalent concern. Research has been conducted examining fre... more Concussion in American football is a prevalent concern. Research has been conducted examining frequencies, location, and thresholds for concussion from impacts. Little work has been done examining how impact location may affect risk of concussive injury. The purpose of this research was to examine how impact site on the helmet and type of impact, affects the risk of concussive injury as quantified using finite element modelling of the human head and brain. A linear impactor was used to impact a helmeted Hybrid III headform in several locations and using centric and non-centric impact vectors. The resulting dynamic response was used as input for the Wayne State Brain Injury Model to determine the risk of concussive injury by utilizing maximum principal strain as the predictive variable. The results demonstrated that impacts that occur primarily to the side of the head resulted in higher magnitudes of strain in the grey and white matter, as well as the brain stem. Finally, commonly wo...
Trauma, 2016
Much of what is known concerning human brain injury thresholds is based upon impacts to cadavers ... more Much of what is known concerning human brain injury thresholds is based upon impacts to cadavers and animal models that were used to generate the Wayne State Concussion Tolerance Curve (WSTC) and similar curves. These curves are the foundation for predictive metrics used in standard development as well as helmet design. These curves were based upon a very narrow range of impacts; impacts whose characteristics differ greatly from how the head is impacted in sport. This research examines the uses of time-based curves like the WSTC in the context of understanding mechanisms of brain injury and head protection. Published linear/rotational acceleration magnitude/duration data from Hybrid III laboratory reconstructions of brain injury events were plotted. This research further develops the understanding of injury thresholds in comparison to threshold curves such as the WSTC and Brain Injury Curve Leuven. The data demonstrate the relationships between magnitude and duration of dynamic resp...
Ice hockey has been identified as having one of the highest concussion rates. The three most like... more Ice hockey has been identified as having one of the highest concussion rates. The three most likely causes of concussive injury are; falls to the ice, shoulder to head impacts and punches to the head. The purpose of this study was to examine how these three mechanisms of injury in the sport of ice hockey influence the dynamic response of the head form and the magnitude and distribution of maximum principal strain in the cerebrum. The three impact mechanisms were simulated using a Hybrid III head and neck form attached to a linear impactor, pendulum or monorail system. Three dimensional linear and rotational acceleration data from each impact condition were used to undertake finite element modeling to calculate maximum principal strain in regions of brain tissue. The results indicated that each mechanism incurred a unique peak resultant linear and rotational acceleration response. The maximum principal strain magnitudes were found to be largest in the fall to the ice. The regions of the brain incurring the largest deformation varied per mechanism of injury. This variation of peak magnitude per brain region might explain the differences in symptomology for concussion. Furthering the understanding of these mechanisms would aid in improving the safety of the game.
International Journal of Crashworthiness
ABSTRACT This research focuses on describing the differences between mild traumatic brain injury ... more ABSTRACT This research focuses on describing the differences between mild traumatic brain injury (mTBI) and focal traumatic brain injury (fTBI). The purpose of this research was to compare clinical mTBI and fTBI groups who incurred brain injury from falls to hard surfaces to identify clinical and biomechanical factors that may delineate between these two outcomes. Reconstructions of mTBI (n = 11) and fTBI (n = 20) cases that resulted from falls presented themselves at the hospital were conducted using computational and physical models. The cases were compared using peak and component dynamic response, brain injury criterion (BrIC), Gadd severity index and head injury criterion. Peak resultant rotational acceleration had the best percentage correct classification with 50% risk of severe TBI was found to be 21 krad/s2. The BrIC and component acceleration and rotational velocity of impact were also found to have significant predictions of risk between the two groups. This data provides information to improve risk thresholds for fTBI with application to helmet standards/development.
Journal of Concussion
Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur... more Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur in a multitude of different environments. Each event is composed of combinations of impact characteristics (striking velocity, impact mass, and surface compliance) that present unique loading conditions on the head and brain. The purpose of this study was to compare falls, collisions, and punches from accident reconstructions of sports-related head impacts using linear, rotational accelerations and maximal principal strain of brain tissue from finite element simulation. Methods This study compared four types of head impact events through reconstruction. Seventy-two head impacts were taken from medical reports of accidental falls and game video of ice hockey, American football, and mixed-martial arts. These were reconstructed using physical impact systems to represent helmeted and unhelmeted falls, player-to-player collisions, and punches to the head. Head accelerations were collected us...
B-08-334 In North America alone, concussion occurs at least 1.7 million times a year, and account... more B-08-334 In North America alone, concussion occurs at least 1.7 million times a year, and accounts for approximately 75% of all traumatic brain injuries. Concussion is commonly identified in two categories: transient and persistent concussive syndrome (PCS), in which symptoms last more than one month. Past biomechanical research has investigated sporting concussion [1,2], but no research has been conducted examining the unique characteristics that are connected to PCS. The purpose of this research is to undertake in-depth reconstructions of known persistent concussive syndrome cases and examine the brain tissue stresses and strains resulting from the impacts. A total of 21 persistent concussive syndrome subjects volunteered for this research, consisting of: 11 falls, 8 collisions, and 2 blunt projectile impacts. A medical doctor identified that persistent concussive symptoms were present in each case for longer than one month. A report form was filled out through patient interviews that described the conditions surrounding the impact, such as: velocity, contact surface, impacting mass, etc. Where possible, MADYMO simulations were conducted to identify the impact velocity of the head, which allowed a series of Hybrid III anthropometric dummy reconstructions to be conducted. This, in turn, generated the loading curves for use in the University College Dublin Brain Trauma Model for a three-dimensional finite element analysis. The dependent variables used in this analysis were maximum principal strain, von Mises stress (VMS), strain rate, and product of strain and strain rate. For maximum principal strain alone there were large regions of brain tissue incurring 30 to 40% strain. This large field of strain was also evident when using strain rate, product of strain and strain rate. In addition, VMS also showed large magnitudes of stress throughout the brain tissues. Averaged results across all 21 cases are presented in Table 1. The distribution of stresses and strains throughout the brain indicated the peaks were always in the grey matter, with the white matter showing significantly lower strains (0.481 vs. 0.380, p=0.000). These strain levels were closer to those associated with TBI than with concussion, however the data ranged from values below published concussion thresholds (0.19-0.26)[1,2] to above those for TBI (0.14-0.53)[3].
Sport helmets used by children are governed by the same impact performance requirements as those ... more Sport helmets used by children are governed by the same impact performance requirements as those used by adults. While many standards use variable mass head-forms in assessing the suitability of such helmets in protecting against traumatic head injury due to blunt trauma, the failure criterion is the same regardless of head-form size. Using existing literature values for important mechanical and physical characteristics of children's heads (such as skull thickness, strength of skull bone, mass and bulk modulus of the brain, etc.), this paper explores the need for a sport helmet intended specifically for children and some of the important performance criteria required for consideration. A simple model of the head-helmet system is used to suggest that impact protection for children requires a combination of material thickness and density to produce helmet liners that are "softer" than those often used in present day helmets. Helmet failure criteria based upon the dynamic fracture tolerance of skull bone in children are proposed and hockey helmets are examined in relation to such by determining the force on the head in targeted impacts of 150 g and 275 g. It is suggested that the current failure limits of 275g-300g , used in many helmet standards, should be re-examined.
Sports biomechanics / International Society of Biomechanics in Sports, Jan 8, 2015
Goaltenders in ice hockey are the only players that are on the ice for the entire game. Their pos... more Goaltenders in ice hockey are the only players that are on the ice for the entire game. Their position exposes them to impacts from collisions with other players, falls to the ice, and puck impacts. In competitive ice hockey leagues, head injuries resulting from puck impacts have been reported with some cases resulting in ending the player's career. Considerable research has been conducted to assess the performance of hockey helmets; however, few have assessed the performance of goaltenders' masks. The purpose of this study was to compare the capacity of four goaltenders' masks for the protection from puck impact as measured by head acceleration and peak force. A Hybrid III headform was fitted with four different goaltender masks and impacted with a hockey puck in three locations at 25 m/s. The masks were found to vary in the level of protection they offered as the mask with the thickest liner resulted in lower forces than the thinnest mask for side impacts; however, the...
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2016
Brain injuries are prevalent in the sport of American football. Helmets have been used which effe... more Brain injuries are prevalent in the sport of American football. Helmets have been used which effectively have reduced the incidence of traumatic brain injury, but have had a limited effect on concussion rates. In an effort to improve the protective capacity of American football helmets, a standard has been proposed by National Operating Committee on Standards for Athletic Equipment that may better represent helmet-to-helmet impacts common to football concussions. The purpose of this research was to examine the National Operating Committee on Standards for Athletic Equipment standard and a new impact method similar to the proposed National Operating Committee on Standards for Athletic Equipment standard to examine the information these methods provide on helmet performance. Five National Operating Committee on Standards for Athletic Equipment–certified American football helmets were impacted according to the National Operating Committee on Standards for Athletic Equipment standard te...
Journal of Concussion
Head injuries in elite and youth sport have garnered growing public attention in part because of ... more Head injuries in elite and youth sport have garnered growing public attention in part because of high-profile cases of professional athletes suffering career-ending/threatening concussions and because of the increase in medical studies identifying how repeated concussive events can lead to long-term health problems, most notably degenerative brain disease. Public concerns around youth ice hockey are intensifying in light of recent evidence which suggests that effects of head injury are worse for youth than they are for athletes in later stages of life. To better understand concussion injury rate trends across all levels of youth hockey, this paper provides a retrospective analysis of concussion related hockey injury as recorded in Hockey Canada’s Injury Reporting System from the period covering 2009 to 2016, combined with two years of observational research documenting head contact events in minor hockey in the Ottawa and Gatineau regions of Ontario and Quebec. By comparing two diff...
Sports Engineering
Helmet design and development are an important tool to help mitigate the severity and frequency o... more Helmet design and development are an important tool to help mitigate the severity and frequency of head and brain injury in sport and everyday life. Helmet assessment protocols and standards often use the Hybrid III neckform as part of the impacting equipment even though it has a biased response that can affect the results. This research presents an unbiased neckform that can be used for the purposes of head impact testing that does not provide a mechanical directional bias to the impact result. A Hybrid III headform was impacted under a sporting impact protocol with a Hybrid III and an unbiased neckform. The resultant acceleration magnitudes were similar between the two necks, while larger differences (8 g and up to 4 krad/s2) were found between the acceleration components. The Hybrid III neck may have a more biased response for longer duration events (10 ms+) as this research considered only short duration impacts (5–10 ms).
Computer methods in biomechanics and biomedical engineering, 2018
Concussion in American football is a prevalent concern. Research has been conducted examining fre... more Concussion in American football is a prevalent concern. Research has been conducted examining frequencies, location, and thresholds for concussion from impacts. Little work has been done examining how impact location may affect risk of concussive injury. The purpose of this research was to examine how impact site on the helmet and type of impact, affects the risk of concussive injury as quantified using finite element modelling of the human head and brain. A linear impactor was used to impact a helmeted Hybrid III headform in several locations and using centric and non-centric impact vectors. The resulting dynamic response was used as input for the Wayne State Brain Injury Model to determine the risk of concussive injury by utilizing maximum principal strain as the predictive variable. The results demonstrated that impacts that occur primarily to the side of the head resulted in higher magnitudes of strain in the grey and white matter, as well as the brain stem. Finally, commonly wo...
Trauma, 2016
Much of what is known concerning human brain injury thresholds is based upon impacts to cadavers ... more Much of what is known concerning human brain injury thresholds is based upon impacts to cadavers and animal models that were used to generate the Wayne State Concussion Tolerance Curve (WSTC) and similar curves. These curves are the foundation for predictive metrics used in standard development as well as helmet design. These curves were based upon a very narrow range of impacts; impacts whose characteristics differ greatly from how the head is impacted in sport. This research examines the uses of time-based curves like the WSTC in the context of understanding mechanisms of brain injury and head protection. Published linear/rotational acceleration magnitude/duration data from Hybrid III laboratory reconstructions of brain injury events were plotted. This research further develops the understanding of injury thresholds in comparison to threshold curves such as the WSTC and Brain Injury Curve Leuven. The data demonstrate the relationships between magnitude and duration of dynamic resp...
Ice hockey has been identified as having one of the highest concussion rates. The three most like... more Ice hockey has been identified as having one of the highest concussion rates. The three most likely causes of concussive injury are; falls to the ice, shoulder to head impacts and punches to the head. The purpose of this study was to examine how these three mechanisms of injury in the sport of ice hockey influence the dynamic response of the head form and the magnitude and distribution of maximum principal strain in the cerebrum. The three impact mechanisms were simulated using a Hybrid III head and neck form attached to a linear impactor, pendulum or monorail system. Three dimensional linear and rotational acceleration data from each impact condition were used to undertake finite element modeling to calculate maximum principal strain in regions of brain tissue. The results indicated that each mechanism incurred a unique peak resultant linear and rotational acceleration response. The maximum principal strain magnitudes were found to be largest in the fall to the ice. The regions of the brain incurring the largest deformation varied per mechanism of injury. This variation of peak magnitude per brain region might explain the differences in symptomology for concussion. Furthering the understanding of these mechanisms would aid in improving the safety of the game.
International Journal of Crashworthiness
ABSTRACT This research focuses on describing the differences between mild traumatic brain injury ... more ABSTRACT This research focuses on describing the differences between mild traumatic brain injury (mTBI) and focal traumatic brain injury (fTBI). The purpose of this research was to compare clinical mTBI and fTBI groups who incurred brain injury from falls to hard surfaces to identify clinical and biomechanical factors that may delineate between these two outcomes. Reconstructions of mTBI (n = 11) and fTBI (n = 20) cases that resulted from falls presented themselves at the hospital were conducted using computational and physical models. The cases were compared using peak and component dynamic response, brain injury criterion (BrIC), Gadd severity index and head injury criterion. Peak resultant rotational acceleration had the best percentage correct classification with 50% risk of severe TBI was found to be 21 krad/s2. The BrIC and component acceleration and rotational velocity of impact were also found to have significant predictions of risk between the two groups. This data provides information to improve risk thresholds for fTBI with application to helmet standards/development.
Journal of Concussion
Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur... more Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur in a multitude of different environments. Each event is composed of combinations of impact characteristics (striking velocity, impact mass, and surface compliance) that present unique loading conditions on the head and brain. The purpose of this study was to compare falls, collisions, and punches from accident reconstructions of sports-related head impacts using linear, rotational accelerations and maximal principal strain of brain tissue from finite element simulation. Methods This study compared four types of head impact events through reconstruction. Seventy-two head impacts were taken from medical reports of accidental falls and game video of ice hockey, American football, and mixed-martial arts. These were reconstructed using physical impact systems to represent helmeted and unhelmeted falls, player-to-player collisions, and punches to the head. Head accelerations were collected us...
B-08-334 In North America alone, concussion occurs at least 1.7 million times a year, and account... more B-08-334 In North America alone, concussion occurs at least 1.7 million times a year, and accounts for approximately 75% of all traumatic brain injuries. Concussion is commonly identified in two categories: transient and persistent concussive syndrome (PCS), in which symptoms last more than one month. Past biomechanical research has investigated sporting concussion [1,2], but no research has been conducted examining the unique characteristics that are connected to PCS. The purpose of this research is to undertake in-depth reconstructions of known persistent concussive syndrome cases and examine the brain tissue stresses and strains resulting from the impacts. A total of 21 persistent concussive syndrome subjects volunteered for this research, consisting of: 11 falls, 8 collisions, and 2 blunt projectile impacts. A medical doctor identified that persistent concussive symptoms were present in each case for longer than one month. A report form was filled out through patient interviews that described the conditions surrounding the impact, such as: velocity, contact surface, impacting mass, etc. Where possible, MADYMO simulations were conducted to identify the impact velocity of the head, which allowed a series of Hybrid III anthropometric dummy reconstructions to be conducted. This, in turn, generated the loading curves for use in the University College Dublin Brain Trauma Model for a three-dimensional finite element analysis. The dependent variables used in this analysis were maximum principal strain, von Mises stress (VMS), strain rate, and product of strain and strain rate. For maximum principal strain alone there were large regions of brain tissue incurring 30 to 40% strain. This large field of strain was also evident when using strain rate, product of strain and strain rate. In addition, VMS also showed large magnitudes of stress throughout the brain tissues. Averaged results across all 21 cases are presented in Table 1. The distribution of stresses and strains throughout the brain indicated the peaks were always in the grey matter, with the white matter showing significantly lower strains (0.481 vs. 0.380, p=0.000). These strain levels were closer to those associated with TBI than with concussion, however the data ranged from values below published concussion thresholds (0.19-0.26)[1,2] to above those for TBI (0.14-0.53)[3].
Sport helmets used by children are governed by the same impact performance requirements as those ... more Sport helmets used by children are governed by the same impact performance requirements as those used by adults. While many standards use variable mass head-forms in assessing the suitability of such helmets in protecting against traumatic head injury due to blunt trauma, the failure criterion is the same regardless of head-form size. Using existing literature values for important mechanical and physical characteristics of children's heads (such as skull thickness, strength of skull bone, mass and bulk modulus of the brain, etc.), this paper explores the need for a sport helmet intended specifically for children and some of the important performance criteria required for consideration. A simple model of the head-helmet system is used to suggest that impact protection for children requires a combination of material thickness and density to produce helmet liners that are "softer" than those often used in present day helmets. Helmet failure criteria based upon the dynamic fracture tolerance of skull bone in children are proposed and hockey helmets are examined in relation to such by determining the force on the head in targeted impacts of 150 g and 275 g. It is suggested that the current failure limits of 275g-300g , used in many helmet standards, should be re-examined.
Sports biomechanics / International Society of Biomechanics in Sports, Jan 8, 2015
Goaltenders in ice hockey are the only players that are on the ice for the entire game. Their pos... more Goaltenders in ice hockey are the only players that are on the ice for the entire game. Their position exposes them to impacts from collisions with other players, falls to the ice, and puck impacts. In competitive ice hockey leagues, head injuries resulting from puck impacts have been reported with some cases resulting in ending the player's career. Considerable research has been conducted to assess the performance of hockey helmets; however, few have assessed the performance of goaltenders' masks. The purpose of this study was to compare the capacity of four goaltenders' masks for the protection from puck impact as measured by head acceleration and peak force. A Hybrid III headform was fitted with four different goaltender masks and impacted with a hockey puck in three locations at 25 m/s. The masks were found to vary in the level of protection they offered as the mask with the thickest liner resulted in lower forces than the thinnest mask for side impacts; however, the...