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.

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Mild traumatic brain injury (mTBI) is common in youth, especially in those who participate in sport. Recent investigations from our group have shown that asymptomatic children and adolescents with mTBI continue to exhibit alterations in neural activity and cognitive performance compared with those without a history of mTBI. This is an intriguing finding, given that current return-to-learn and return-to-play protocols rely predominately on subjective symptom reports, which may not be sensitive enough to detect subtle injury-related changes. As a result, youth may be at greater risk for re-injury and long-term consequences if they are cleared for activity while their brains continue to be compromised. It is currently unknown whether mTBI also affects brain microstructure in the developing brain, particularly cortical thickness, and whether such changes are also related to cognitive performance. The present study examined cortical thickness in 13 asymptomatic youth (10-14 years old) who had sustained an mTBI 3-8 months prior to testing compared with 14 age-matched typically developing controls. Cortical thickness was also examined in relation to working memory performance during single and dual task paradigms. The results show that youth who had sustained an mTBI had thinner cortices in the left dorsolateral prefrontal region and right anterior and posterior inferior parietal lobes. Additionally, cortical thinning was associated with slower reaction time during the dual-task condition in the injured youth only. The results also point to a possible relationship between functional and structural alterations as a result of mTBI in youth, and lend evidence for neural changes beyond symptom resolution.

Despite growing interest in the biomechanical mechanisms of sports-related concussion, ice hockey and the youth sport population has not been studied extensively. The purpose of this pilot study was: 1) to describe the biomechanical measures of head impacts in youth minor ice hockey players; and, 2) to investigate the influence of player and game characteristics on the number and magnitude of head impacts. Data was collected from 13 players from a single competitive Bantam boy's (ages 13-14 years) AAA ice hockey team using telemetric accelerometers implanted within the players' helmets at 27 ice hockey games. The average linear acceleration, rotational acceleration, Gadd Severity Index and Head Injury Criterion of head impacts were recorded. A significantly higher number of head impacts per player per game were found for wingers when compared to centre and defense player positions (df=355, t=3.087, p=0.00218) and for tournament games when compared to regular season and playoff games (df=355, t=2.641, p=0.086). A significant difference in rotational acceleration according to player position (F2,1812=4.9551, p=0.0071) was found. This study is an initial step towards a greater understanding of head impacts in youth ice hockey.

Background:Postural stability plays a key role in sport performance, especially after concussion. Specific to healthy child and youth athletes, little is known about the influence development and sex may have on postural stability while considering other subjective clinical measures used in baseline/preinjury concussion assessment. This study aims to describe age- and sex-based trends in postural stability in uninjured child and youth athletes at baseline while accounting for concussion-related factors.Hypotheses:(1) Postural stability performance will improve with age, (2) females will display better postural stability compared to males, and (3) concussion-like symptoms will affect postural stability performance in healthy children and youth.Study Design:Cross-sectional study.Level of Evidence:Level 3.Methods:This study comprised 889 healthy/uninjured child and youth athletes (54% female, 46% male) between the ages of 9 and 18 years old. Participants completed preseason baseline testing, which included demographic information (age, sex, concussion history), self-report of concussion-like symptoms (Post-Concussion Symptom Inventory [PCSI]–Child and PCSI-Youth), and measures of postural stability (BioSway; Biodex Medical Systems). Two versions of the PCSI were used (PCSI-C, 9- to 12-year-olds; PCSI-Y, 13- to 18-year-olds). Postural stability was assessed via sway index under 4 sway conditions of increasing difficulty by removing visual and proprioceptive cues.Results:In children aged 9 to 12 years old, there were significant age- (P < 0.05) and sex-based effects (P < 0.05) on postural stability. Performance improved with age, and girls performed better than boys. For youth ages 13 to 18 years old, postural stability also improved with age (P < 0.05). In both child and youth subgroups, postural stability worsened with increasing concussion-like symptoms (P < 0.05).Conclusion:There are developmental and baseline symptom trends regarding postural stability performance.Clinical Relevance:These findings provide a preliminary foundation for postconcussion comparisons and highlight the need for a multimodal approach in assessing and understanding physical measures such as postural stability.