Within-Day Energy Balance and the Relationship to Injury Rates in Pre-Professional Ballet Dancers.

Introduction: Ballet dancers’ body weight and BMI have been shown to be below recommended levels, and total energy intake is often sustained at a level below the predicted energy requirement. Less is known about the ability of dancers to manage energy balance (EB) during the day, as energy requirements fluctuate as a result of periods of rest and intense activity. Compromised EB may result in decreased athletic performance, higher body fat percentage, and increased injury risk. Purpose: To assess within-day energy balance (WIDEB) during a typical training day in a group of pre-professional ballet dancers and dancers in the early years of professional careers, and to assess the relationship between inadequate EB and injury rates in these dancers. Methods: A two part assessment tool was developed to measure energy intake and energy expenditure hour by hour within a single 24 hour time period. Body mass index (BMI), resting energy expenditure, total day energy balance, and energy deficits \u3e -400 kcal were also used in analysis. Participants were asked to document number of injuries incurred within the previous dance season, and how many days the injury resulted in one or more complete or partial sessions of time lost beyond the injury itself. Data analysis included descriptive statistics, t-tests, and Spearman’s correlation to evaluate relationships between EB and injury rates. Results: Data were collected from 21 (5 males, 16 females) pre-professional and professional ballet dancers from the Atlanta Ballet. Average BMI was 21.9 ±1.4 for male dancers (MD) and 19.1 ±1.0 for female dancers (FD). Negative energy balance (EB) was found at hour 24 in 90.5% participants. Average energy intake for all dancers was 2,382 kcal (± 921) and the average predicted energy expenditure was 3,317 kcal (± 592). Mean EB at hour 24 for all participants was -781.2 (±689.4). The average day EB for males was -223.6 (±629.7) and -1156.9 (±582.5) for females. The largest energy deficits (\u3e900 kcal) compared to estimated expenditures were found between the hours 17 and 20. Participants spent an average of 660.0 (±192.6) minutes per day in negative EB \u3e - 400 kcal. Total group (TG) injury days and energy deficit data (number of minutes \u3e - 400 kcal) were not significantly correlated. Number of minutes \u3e - 400 kcal and number of injuries reported per dancer were correlated (r = -0.44 P = 0.046). MD (n = 5) injury days were significantly associated with EB at hours 1 through 7 (r = 0.90 P = 0.37). MD total number of times injured was associated with EB at hours 1 through 7 (r = 0.89 P = 0.04). A significant association was found in FD between number of times injured and deficits \u3e - 400 kcal. Conclusions: Ballet dancers have significant energy deficits during a typical training day therefore increasing their risk for injuries. Nutrition education would be a key component of an injury prevention program for dancers