title: Does bone-targeted training reduce bone injury-related time loss to dancing in preprofessional classical ballet dancers? BalletMor: A feasibility study
Creators: name: Drysdale, Louise
Publisher: name: Griffith University
Year: 2021
Subjects: subject: HiRIT
subject: bone-related injury
subject: resistance and impact training

description: Pre-professional ballet dancers are at risk of injury to bone, particularly stress reactions and stress fractures. Low energy availability (LEA), high number of training hours, irregular menstruation, and subsequent poor bone health are factors that may increase this risk. Bone stress injuries (BSI) result in long periods of rehabilitation for young dancers, negatively affect career progression and may indicate poor bone or systemic health, which can affect quality of life in later years. Such injuries occur due to repeated load exposures below the fracture threshold of bone. Whilst the benefits of supplementary resistance training in ballet have been explored with aims to improve performance and reduce injury, there has been no specific focus on reducing bone-related injury. Conversely, resistance training incorporated into youth sports training may reduce risk of injury by up to 68%. Additionally, jumping and multidirectional loading exercises have been shown to improve bone health in adolescents and athlees respectively. High intensity, resistance and impact training (HiRIT) improves bone health in older persons who have low bone density. Thus, it is possible that HiRIT may improve bone density and reduce bone stress injuries in adolescent female ballet dancers. Before large scale testing is considered, the feasibility of HiRIT in an elite ballet setting must be tested. Methods Eighteen female adolescent dancers (baseline age 16.6 ±1.6yrs) training more than 12 hours per week from an elite training school in Brisbane, Queensland were recruited to participate in twice-weekly HiRIT for eight months. Participants completed exercise diaries to determine compliance and progress in the HiRIT. Ballet students and their teachers completed separate researcher-designed, Likert scale questionnaires to gauge satisfaction (perceived worth, enjoyment and benefits) with the HiRIT program. Student participants recalled the previous 12 months injuries pre- and postintervention, estimating days of complete rest and/or modified dance. Bone mass was estimated with dual energy X-ray absorptiometry (DXA) at study commencement and completion, along with trunk extensor strength (kg), simple anthropometrics (height, weight, lower limb girth), and double and single leg jump height (m). A calcium intake questionnaire (AusCal) and the Low Energy Availability in Females Questionnaire (LEAF-Q) were completed to determine menstrual irregularity and identify potential LEA. Exercise history and lower limb hypermobility was also determined. Adverse events were recorded. Recruitment, attendance, and loss to follow up were recorded as percentages. A paired t-test was used to analyse responses to student satisfaction questionnaires of HiRIT (acceptability) and a one sample t-test was used to determine teacher acceptance of HiRIT. A Wilcoxon Rank Signed Test determined differences in days rest and days modified due to injury. Mean percent change for other secondary outcomes was determined. Pearson and Spearman correlations of secondary outcomes were conducted to explore trends, depending on normality testing. COVID19 Note The intervention phase of this study was conducted in 2020 and halted by the unprecedented coronavirus pandemic. Dancers had completed one month of a planned 8- month HiRIT program. A framework for return to sport in a COVID19 environment has been released by the Australian Institute of Sport, detailing events leading to COVID19 arriving in Australia. During the pandemic, dancers were confined to their homes. Modified ballet training was continued via video conference, but it was not possible to continue HiRIT activities. No participants were confirmed to have contracted COVID19. Ballet training returned face to face after 9-11 weeks of isolation. The HiRIT program recommenced two weeks after returning from isolation and resuming normal training. Total HiRIT training time was reduced from 35 weeks to between 23 and 26 weeks. Results HiRIT was not feasible in terms of recruitment (36% of eligible female ballet students) or compliance (60.2 ±18.8) %, however loss to follow up was lower than the anticipated 30% (19%). The program was acceptable (scores ± 30/50) to ballet students (44.0 ± 4.2), p = 0.019, but not to their ballet teachers (22.6 ± 6.4), p = 0.6. Time lost (days of rest or modified training) due to injury was not reduced, nor was the incidence of BSI. No adverse events were recorded. Mean percent improvement in whole body bone mineral density (BMD) (3.63 ± 4.33) and bone mineral content (BMC) (5.11 ± 4.37), lumbar spine BMD (3.23 ± 2.62) and BMC (5.55 ± 3.59), and forearm and back extensor strength (22.16 ± 23.84) were observed. Conclusion HiRIT was not feasible in an elite ballet training institution, due to low recruitment numbers and low compliance. Numbers lost to follow up were low and no adverse events were recorded. Ballet students accepted HiRIT, however ballet teachers did not. There was no reduction in time loss injuries. Future controlled trials or longitudinal follow up are required to determine the clinical significance of bone and performance effects of HiRIT.