Background Physical rest after a concussion has been described as a key component in the management of the injury. Evidence supporting this recommendation, however, is limited. Purpose To examine the association between physical activity and symptom duration in a cohort of patients after a concussion. Study Design Cohort study; Level of evidence, 2. Methods This study included 364 patients who were diagnosed with a concussion, were seen by a physician within 3 weeks of injury, and completed a questionnaire at the initial clinic visit. The questionnaire assessed the postconcussion symptom scale (PCSS) score, previous number of concussions, presence of the loss of consciousness or amnesia at the time of injury, and prior treatment for headaches. During each follow-up clinic visit, physical activity level was self-reported. A Cox proportional hazard model was constructed to determine the association between symptom duration, initial clinic visit responses, and self-reported physical activity level after the injury. Results Study participants ranged in age from 8 to 27 years (mean age, 15.0 years) and had sustained a mean of 0.8 prior concussions; 222 patients (61%) were male. On initial examination, the mean PCSS score was 34.7. The mean symptom duration was 48.9 days after the injury. Among the variables included in the model, initial PCSS score and female sex were independently associated with symptom duration, while physical activity level after the injury was not. For participants aged between 13 and 18 years, however, higher levels of physical activity after the injury were associated with a shorter symptom duration. Conclusion Results from this study indicate that physical activity after the injury may not be universally detrimental to the recovery of concussion symptoms.

Background Adolescent ballet dancers have a higher incidence of injury than adult professional dancers. It is unclear which factors, including biomechanical changes related to intense dance training and/or the growth process itself, contribute to increased injury risk in this population. Objective To assess changes in strength, flexibility, and functional performance in adolescent ballet dancers during a summer intensive dance program. Design Prospective cohort study. Setting Performing arts school in a suburb of Massachusetts. Participants A convenience sample of 58 male and female ballet dancers, 12 to 17 years old, was enrolled. One dancer did not have functional testing due to injury, but strength and range of motion results were included. Methods Paired sample t‐test was used to evaluate changes in (1) strength: lower abdominal muscle strength evaluated by the Kendall double leg lowering test; (2) flexibility: passive range of motion in hip extensibility, hip internal rotation, hip external rotation, hip turnout, and ankle dorsiflexion; and (3) functional athletic and dance assessment: the star excursion balance test (SEBT), vertical jump test, and dance technique performing demi‐plié and passé dance positions. Main Outcome Measurements Change in strength, flexibility, and functional dance measurements pre‐ and postsummer intensive dance training. Results Lower abdominal strength testing improved 11° on the Kendall test (P < .001); lower extremity passive flexibility was reduced in all tested ranges bilaterally. Dance technique, in performing demi‐plié and passé dance positions, improved. More dancers demonstrated correct knee alignment during demi‐plié (P < .001‐.002) and hip alignment during plié (P = .01‐.04). Dancers also had greater active hip turnout in first position passé of 2 to 3° (P = .02‐.05). No significant change was found in functional athletic performance as measured by the SEBT and vertical jump test. Conclusion Adolescent dancers in this study cohort who participated in a summer intensive dance program improved lower abdominal muscle strength as well as functional dance technique in demonstrating correct alignment performing demi‐plié and passé dance positions despite a decrease in passive lower extremity range of motion. Further research is needed to clarify the role of these findings in training for young dancers in order to move forward injury prevention efforts. Level of Evidence II

Objective: To examine CrossFit-related injuries based on sex and age. Design: Retrospective case series. Setting: A tertiary-level pediatric sports medicine clinic. Participants: CrossFit athletes. Main Outcome Measures: CrossFit-related injuries by sex (males vs females) and age groups (≤19 years vs >19 years) using a χ2 analysis with P = 0.05, odds ratio (OR), and 95% confidence interval (95% CI). Results: Among injured CrossFit athletes, female athletes sustained lower extremity injuries more frequently than male athletes (P = 0.011; OR, 2.65; 95% CI, 1.25-5.65). In observed CrossFit injuries, shoulder injuries were more frequently observed in male athletes compared with female athletes (P = 0.049; OR, 2.79; 95% CI, 0.98-7.95). Additionally, a greater proportion of CrossFit athletes aged 19 years and younger suffered trunk/spine injuries than those older than 19 years (P = 0.027; OR, 2.61; 95% CI, 1.10-6.21) in injured CrossFit athletes. Conclusions: The current results indicated sex- and age-specific susceptibility to CrossFit-related injuries based on body parts and diagnoses. The presented information may be useful to develop a safer exercise program, especially for pediatric and adolescent CrossFit participants.