Could Eccentric Resistance Training be Effective for Youth Female Ballet Dancers? A Pilot Study

Introduction
Ballet is a demanding activity which requires jumping and landing (Ekegren et al. 2014, Bowerman et al. 2015). In particular, jumping is a key quality that dancers must posses since jump height is associated with successful dance performance (Dowse, McGuigan & Harrison. 2020). However, for dancers to achieve professional standard they are required to early specialise (Ekegren et al. 2014). Consequently, the repetitive jumping and landing experienced by dancers can cause injuries in pre-professional dancers (Bowerman et al. 2015). Therefore, training methods that can positively impact both performance and injury risk factors in young female dancers are needed. Therefore, this pilot study investigated the effects of Eccentric Resistance Training (ERT) in youth female ballet dancers.

Methods
A within-between group, repeated measures experimental design was undertaken to assess changes in jumping and landing performance following five weeks of ERT or usual dance-studio based strength training (DBST) performed once per week. Eight female youth ballet dancers (age 16 ± 1.5 years) participated in the intervention (ERT group = 5, DBST group = 3). Pre and post measures of jump height (H), reactive strength index (RSI) and time to stabilization (TTS) from the countermovement jump (CMJ), Drop jump (DJ) and Unilateral Drop Landing (DL) tests were completed, respectively. Pre to post training change scores were calculated via delta values (%) and individual change scores as outlined by Turner (2022). Ethical approval was provided by the Hartpury University Ethics Committee (ETHICS2021-62).

Results
CMJ Height: Greater absolute and relative improvements were found in the ERT group (2.32 ± 0.98cm, 10% ± 4.2%), compared with the DBST group (1.1 ± 3.86cm, 5.6% ± 15.5%) in the usual training group. DJ RSI: Greater absolute and relative improvements were found in the ERT group (0.47 ± 0.28, 39.8% ± 31.7%), compared with the DBST group (0.35 ± 0.42, 28% ± 30.5%). DL TTS: Increased absolute and relative times were found in the ERT group (0.22 ± 0.11s, 43.7% ± 11.9%), compared with lowered times in the DBST group (0.09 ± 0.03s, 19.1% ± 8.3%).

Practical Applications
The initial findings from this pilot study suggest ERT may be a useful “dual” tool that coaches can use enhance both physical qualities and injury risk factors in young female ballet dancers. Since the majority of the exercises used in the ERT programme are affordable and easy to implement, the training programme outlined here provides a sustainable and inclusive approach that coaches can use. Whilst the findings suggest that ERT may be favorable compared to DBST training for some jumping based movements, a subsequent study with increased sample size and analysis of force-time measures from the jumping tasks is required to better assert the efficacy of ERT for young female athletes.