Tim Taha

Systems Modelling of the Relationship Between Training and Performance

Mathematical models may provide a method of describing and predicting the effect of training on performance. The current models attempt to describe the effects of single or multiple bouts of exercise on the performance of a specific task on a given day. These models suggest that any training session increases fitness and provokes a fatigue response. Various methods of quantifying the training stimulus (training impulse, absolute work, psychophysiological rating) and physical performance (criterion scale, arbitrary units) are employed in these models. The models are empirical descriptions and do not use current knowledge regarding the specificity of training adaptations. Tests of these models with published data indicate discrepancies between the predicted and measured time course of physiological adaptations, and between the predicted and measured performance responses to training. The relationship between these models and the underlying physiology requires clarification. New functional models that incorporate specificity of training and known physiology are required to enhance our ability to guide athletic training, rehabilitation and research.

Imaging "brain strain" in youth athletes with mild traumatic brain injury during dual-task performance

Mild traumatic brain injury (mTBI) is a common cause of injury in youth athletes. Much of what is known about the sequelae of mTBI is yielded from the adult literature, and it appears that it is mainly those with persistent post-injury symptoms who have ongoing cognitive and neural abnormalities. However, most studies have employed single-task paradigms, which may not be challenging enough to uncover subtle deficits. We sought to examine the neural correlates of dual-task performance in male athletes aged 9-15 years using a functional neuroimaging protocol. Participants included 13 youths with a history of mTBI three to six months prior to testing and 14 typically-developing controls. All participants completed a working memory task in isolation (single-task) and while completing a concurrent motor task (dual-task); neural activity during performance was then compared between groups. Although working memory performance was similar during the single-task condition, increased working memory load resulted in an altered pattern of neural activation in key working memory areas (i.e., dorsolateral prefrontal and parietal cortices) in youth with mTBI relative to controls. During the dual-task condition, accuracy was similar between groups but injured youth performed slower than typically-developing controls, suggesting a speed-accuracy tradeoff in the mTBI group only. The injured youths also exhibited abnormal recruitment of brain structures involved in both working memory and dual-tasking. These data show that the dual-task paradigm can uncover functional impairments in youth with mTBI who are not highly symptomatic and who do not exhibit neuropsychological dysfunction. Moreover, neural recruitment abnormalities were noted in both task conditions, which we argue suggests mTBI-related disruptions in achieving efficient cognitive control and allocation of processing resources.

Increasing Task Complexity and ICE Hockey Skills of Youth Athletes

The objective of this pilot study was to investigate the effects on cognitive performance of progressively adding tasks specific to ice hockey (skating, stick handling, and obstacle avoidance) during a visual interference task (Stroop Color Word Test–interference condition). In addition, the effects on locomotor performance of progressively adding tasks of stickhandling, visual interference, and obstacle avoidance related to maximal skating speed and minimal obstacle clearance were investigated in eight male athletes ages 10 to 12 years. Results revealed decreased performance on both cognitive and physical measures with increased task complexity, suggesting that adding complexity to an environment influences hockey skill performance.

Developmental and gender influences on executive function following concussion in youth hockey players

Abstract Background: Concussion is the most common athletic injury in youth who are simultaneously undergoing rapid developmental changes in the brain, specifically the development of executive functions (EF). The developing brain is more vulnerable to concussive injury with a protracted and different trajectory of recovery than that of adults. Thus, there is a critical need to enhance understanding of how concussion affects EF in youth. Objective: To investigate the effects of age, gender and concussion history (i.e. concussion incidence, recency, severity) on EF in youth hockey players. Methods: This 3-year cross-sectional and longitudinal multiple cohort study examined data from 211 hockey players of 8–15 years of age. Mixed-effects modelling was used to examine the influence of age, gender and concussion on EF in youth athletes. Findings: Baseline analyses revealed significant age and gender effects on measures of EF. Multiple effects of concussion history on measures of cognitive flexibility (F = 2.48, p = 0.03) and psychomotor speed (F = 2.59, p = 0.04) were found. Implications: This study highlights the impact of age, gender and concussion on EF in youth. These findings provide foundational knowledge to better manage cognitive sequelae following sports-related concussion.

Age and competition level on injuries in female ice hockey.

The objective of this study was to describe the number, types and locations of known injuries occurring across different age categories and levels of competition in female ice hockey within the Ontario Womens Hockey Association from 2004/05 to 2007/08. We further examined under which aforementioned factors and combination of factors an unusually high or low number of injuries was recorded. Secondary analysis of anonymized injury data was conducted. The most common known injury type was strain/sprain, followed by concussion while the most frequent injury location was head/face/mouth. Analysis of deviance indicated that a significantly higher than expected number of sprain/strain, concussion and laceration injuries were recorded compared to all other injury types. In addition, there were a higher number of injuries recorded at the AA level compared to all other levels of competition. Finally, the age categories of Peewee, Midget and Intermediate within the AA level of competition, as well as Senior/Adult within the Houseleague level of competition also recorded a significantly higher number of injuries compared to other combinations of descriptive factors. Further research with female youth is needed to better understand the high number of injuries, including concussions, reported overall.

Concussion and Concurrent Cognitive and Sport-specific Task Performance in Youth Ice Hockey Players: A Single-case Pilot Study

Background: Concussion is common in the sport of ice hockey and can cause deficits in cognitive function. In most situations, ice hockey participation requires the performance of more than one skill at a time. It has been reported that following concussion in athletes, performance deficits arise when locomotor and cognitive tasks are performed concurrently that may have otherwise gone unnoticed if assessed in isolation of one another. The purpose of this pilot study was to explore the effect of concussion on cognition during concurrent ice hockey specific tasks in youth ice hockey players. Methods: This single case pilot study compared the performance of 4 male youth ice hockey players who had experienced a concussion in the previous ice hockey season (mean age=11.7 ± 0.3 years; mean time since injury=92.5 ± 49.1 days) to a group of 10 non-injured controls (mean age=11.8 ± 0.8 years). Participants completed a randomized combination of three ice hockey specific tasks while concurrently completing a visual interference task (modified Stroop task). Results: Participants who experienced a concussion within the previous ice hockey season and were ≤ 58 days post-injury demonstrated significantly poorer cognitive performance (increased cognitive dual task cost) across all conditions when completing the visual interference task concurrently with ice hockey specific skills (p ≤ 0.05). Conclusion: This study acts as an initial step towards the development of a sport-specific assessment of functional performance following concussion in youth ice hockey players to help inform safer return to play.

Relationships among Risk Factors for Concussion in Minor Ice Hockey

There is increasing concern among parents, coaches, and officials about injury risk in youth ice hockey, particularly in light of recent evidence suggesting that incidence of serious injury is considerably under reported. However, an adequate method for ascertaining injury risk for concussion does not yet exist. The purpose of this study was to examine the relationships among variables measuring exposure and head impact forces in a group of representative level bantam aged hockey players. Across an entire hockey season, trained research assistants attended games and recorded the duration of time spent on the ice for each player (i.e., exposure time) and total number of body contacts using time-on-task software designed specifically for this study. A body contact included any intentional or incidental contact between two players. Collectively, these variables provide a simple, easily administered measure of head injury risk for researchers collecting data in this area. However, their relationship to actual brain trauma is unknown. To this end, head acceleration data were also collected using helmet-based accelerometers that provide measures of linear accelerations experienced by each player. These data were collected by telemetry methods and represent data that are likely very useful for injury researchers but not without sufficient costs. Results demonstrated low associations among the data sources. A method based on combining data sources (through an examination of their potential relationships) is proposed to maximize the potential to identify at-risk youth in minor hockey.

Paediatric sports-related mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a common but relatively understudied childhood injury that can impact cognitive functioning and development. The present report describes a case study of a 14-year-old boy who sustained two consecutive sports-related mTBIs within a 24 h period. Neurocognitive functioning at 2, 6, 8, 55 and 225 days after injury is compared to baseline prior to injury assessment on the same measures. Results from Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT), Conner Continuous Performance Test 2 (CPT-II) and the Attention Network Test (ANT) revealed decreased performance in attention, visual memory functioning and impulsivity, with some measures still not returning to baseline at 225 days post injury. The results are discussed with respect to return to normal activities at 4 days post injury. This case study highlights the need for increased research regarding the clinical management of mTBI in the paediatric population, particularly the potential deleterious effects of cumulative injuries.

Heart Rate Variability in Healthy Non-Concussed Youth Athletes: Exploring the Effect of Age, Sex, and Concussion-Like Symptoms

Background Heart rate variability (HRV) is a non-invasive neurophysiological measure of autonomic nervous system regulation emerging in concussion research. To date, most concussion studies have focused on the university-aged athlete with no research examining healthy active youths. Corroborating changes in HRV alongside traditional subjective self-report measures (concussion symptoms) in the non-concussed state provides a foundation for interpreting change following concussion. The objectives were to (1) explore the influence of age and sex on HRV and (2) examine the relationship between HRV and baseline/pre-injury concussion symptom domains (physical, cognitive, emotional, and fatigue) in healthy youth athletes. Method Healthy, youth athletes 13–18 years of age [N = 294, female = 166 (56.5%), male = 128 (43.5%)] participated in this cross-sectional study. Age, sex, and concussion-like symptoms were collected as part of a baseline/pre-injury assessment. The Post-Concussion Symptom Inventory-SR13 (PCSI-SR13) was used to collect domain scores for physical, cognitive, emotional, and fatigue symptoms. HRV was collected for 24 h. HRV measures included time (SDNN, RMSSD, and pNN50) and frequency (HF, HFnu, LF, LFnu, and total power) domain HRV measures. Variables were logarithmically transformed to increase robustness of linear regression models. Results Older youth participants displayed significantly higher HRV compared to younger participants (p < 0.05). Females displayed significantly lower HRV compared to males (p < 0.05). A significant interaction effect between concussion-like symptoms and HRV indicated differential patterns as a function of sex (p < 0.05). Youth athletes who reported more cognitive symptoms had lower HRV (p < 0.05). Conclusion HRV was found to have a significant relationship with a traditional clinical measure (subjective self-report of concussion-like symptoms) utilized in concussion assessment and management. Baseline/pre-concussion trends in HRV were significantly associated with age and sex, highlighting the value in understanding key demographic factors within the context of concussion-like symptoms.

Player and Game Characteristics and Head Impacts in Female Youth Ice Hockey Players

CONTEXT   Despite the growing popularity of ice hockey among female youth and interest in the biomechanics of head impacts in sport, the head impacts sustained by this population have yet to be characterized. OBJECTIVES   To describe the number of, biomechanical characteristics of, and exposure to head impacts of female youth ice hockey players during competition and to investigate the influences of player and game characteristics on head impacts. DESIGN   Cohort study. METHODS   Twenty-seven female youth ice hockey players (mean age = 12.5 ± 0.52 years) wore instrumented ice hockey helmets during 66 ice hockey games over a 3-year period. Data specific to player, game, and biomechanical head impact characteristics were recorded. A multiple regression analysis identified factors most associated with head impacts of greater frequency and severity. RESULTS   A total of 436 total head impacts were sustained during 6924 minutes of active ice hockey participation (0.9 ± 0.6 impacts per player per game; range, 0-2.1). A higher body mass index (BMI) significantly predicted a higher number of head impacts sustained per game (P = .008). Linear acceleration of head impacts was greater in older players and those who played the forward position, had a greater BMI, and spent more time on the ice (P = .008), whereas greater rotational acceleration was present in older players who had a greater BMI and played the forward position (P = .008). During tournament games, increased ice time predicted increased severity of head impacts (P = .03). CONCLUSIONS   This study reveals for the first time that head impacts are occurring in female youth ice hockey players, albeit at a lower rate and severity than in male youth ice hockey players, despite the lack of intentional body checking.