The Relationship of Year Group and Sex on Injury Incidence and Countermovement Jump in Adolescent Ballet Dancers: A Cross-Sectional Analysis

Abstract

Introduction: Pre-professional ballet training involves long training hours from an early age that could influence young dancers’ physical performance and injury incidence. This cross-sectional analysis investigated the relationship of year group and sex with countermovement jump and injury incidence (primary outcome) in adolescent ballet dancers at a pre-professional dance school. Method: Countermovement jump (CMJ) height was recorded at the start of the academic year for 179 participants (M = 68, F = 111) spread across eight year-groups. Injury etiology and incidence was prospectively recorded over a 6-month period (September through February) by the medical team using a time-loss definition. Results: Between-subject statistically significant differences were reported for sex [F(1, 153) = 101.46; p < 0.001], year group [F(7, 153) = 12.57; p < 0.001], and sex*year group [F(7, 153) = 9.22; p < 0.001]. Mean CMJ across the year groups ranged between 24.7 to 41.3 cm for males and 23.5 to 25.1 cm for females. Injury incidence per dancer was 0.84 (CI: 0.13, 1.56) and injury incidence per 1,000 hours of dance was 1.94 (CI: 1.63, 2.25). No statistically significant differences between sexes or year groups were reported for injury incidence per 1,000 dance hours and time-loss. Hours dancing was statistically significantly positively associated with CMJ (r = .481, p < 0.05) and negatively associated with injury incidence (r = -.253, p < 0.05) for males; for females it was positively associated with time-loss (r = .254, p < 0.05). Conclusion: Even though CMJ was cross-sectionally monitored, the expected increased physical abilities in males as they grew older and progressed through their training was observed. Females did not indicate a similar increase in their physical ability, but they seemed to become more susceptible to injuries as they grow older. The lack of this speculative physiological development for the females may be associated with the ballet-only approach in their training. The use of CMJ as an injury screening tool may be limited, however, it could still be used as a tool to monitor physiological and fundamental motor skill development of adolescent dancers, as jumping is an integral part of ballet.

The Use of Physical Screening Tools to Identify Injury Risk Within Pre-Professional Ballet Dancers: An Integrative Review

“…Incidence could therefore potentially be reduced by managing dancers during periods when dancers are at heightened risk. Despite the complexities of analysing these factors, this area also warrants further investigation due to the potential influence maturation may have on modifiable physical risk factors, which may mediate injury risk such as strength and ROM [46]. For example, Kolokythas et al [46] found that male pre-professional dancers showed age related increases in jump height whereas female dancers did not.…”

“…Despite the complexities of analysing these factors, this area also warrants further investigation due to the potential influence maturation may have on modifiable physical risk factors, which may mediate injury risk such as strength and ROM [46]. For example, Kolokythas et al [46] found that male pre-professional dancers showed age related increases in jump height whereas female dancers did not. This was accompanied by an age-related increase in injury incidence in the female dancers.…”

The Effects of the 11+ Dance Neuromuscular Program on Jump Height and Lower Extremity Biomechanics in Female Adolescent Dancers: A Non-Randomized Controlled Pilot Trial

“…5 Dancers require a unique blend of physical and artistic skills achieved through years of rigorous training, with training loads, and intensity increasing with age. [6][7][8] Dance is a jump-intensive activity with jumping and landing tasks forming a large component of a dancer's movement repertoire. 9 Due to the aesthetic nature of performance, anecdotal evidence reports that 50% of these jumps are executed via single-leg landings, with some of the larger jumps (eg, grande jeté) creating forces at the knee exceeding 12 times the dancer's body weight.…”

“…11,12 Subsequently, 70% to 80% of pre-professional dancers sustain an injury per year. [6][7][8] Most of these injuries are classified as overuse and occur in the lower extremity. 3,6,8 Numerous studies on female athletes report a link between increased risk of lower extremity injury and inappropriate pattern of lower extremity moments and angles during jumping tasks.…”

“…[6][7][8] Most of these injuries are classified as overuse and occur in the lower extremity. 3,6,8 Numerous studies on female athletes report a link between increased risk of lower extremity injury and inappropriate pattern of lower extremity moments and angles during jumping tasks. [13][14][15][16] The moment of a force is a measure of its tendency to cause a body to rotate about a specific point or axis.…”