Introduction The aim was to study whether six weeks of intensive dance exposure (Swan Lake rehearsals) is a significant contributor to structural changes, symptoms, clinical signs and pain in the Achilles tendon (AT).

Materials and methods Ballet dancers from The Royal Danish Ballet Company (aged 18–41) were invited (n=79) of which sixty-three (80%) dancers participated. Baseline scans were collected with follow-up scans at six weeks. The primary outcome was quantification of AT structure with Ultrasound Tissue Characteristics (UTC) (echo-type I–IV). Secondary outcomes of interest were clinical signs and symptoms gathered from a clinical examination, self-reported symptoms, VISA-A questionnaire and pain during single-legged heel raise. UTC has previously shown to have satisfactory reproducibility and validity. Separate multilevel linear and logistic regression models were performed including time and demographic variables as covariates.

Result From baseline to follow-up there was significant decrease in distribution of UTC echo-type I (β=−3.6,p=0.001;95% CI:−5.8;−1.5) with significant increase in echo-type II (β=3.2,p<0.0001;95% CI:1.6;4.8). Significant effects were also seen, of limb (type I+III) and gender (type I+II). No significant changes were found in clinical outcomes/clinical signs and symptoms.

Conclusion The cohort of ballet dancers showed significant UTC changes, mainly a reduction of echo-type I distribution after six-weeks pre-season period rehearsing Swan Lake ballet. No changes were found in clinical outcomes/clinical signs and symptoms. However, early structural changes seem important to follow longitudinally for potential planning of secondary prevention strategies.