Author(s): ERYIGIT, B., SOYLU, C.1, YAMANER EVLIYAOGLU, G.2, Institution: HEALTH SCIENCES UNIVERSITY, Country: TURKEY, Abstract-ID: 2136

INTRODUCTION:
Ballet places repetitive demands on the ankle–foot complex in en pointe and demi-pointe, requiring frontal-plane stability and rapid posterior-chain force redistribution. Unilateral symptoms or habitual loading may lead to side-to-side differences in muscle architecture and task-specific activation despite similar foot posture. This study quantified between-limb differences in FPI-6, ultrasound-derived architecture of tibialis anterior, peroneals and gastrocnemius (PA, MT, CSA, FL), and %MVIC of GMed, GM/GL and peroneals during a standardised ballet task.
METHODS:
Fifteen ballet dancers were assessed (USG n=14; FPI n=15). Bilateral B-mode USG measured PA, MT and CSA; FL was calculated as MT/sin(PA). FPI-6 was recorded bilaterally. Noraxon sEMG RMS was normalised to MVIC and expressed as %MVIC. USG data were analysed using 2×3 repeated-measures ANOVA (ηp²), paired contrasts with 95% CI and dz, multivariate Hotelling’s T², and FDR correction.
RESULTS:
Foot posture was neutral to mildly pronated and similar between limbs (right 3.0±2.3; left 2.7±1.8; p=0.265). USG revealed limb-specific patterns. For PA, a significant muscle×limb interaction was found (F(2,26)=10.44, p<0.001, ηp²=0.45). TA PA was higher on the right (21.5±5.4°) than the left (16.8±5.4°; p=0.004, dz=0.93), whereas gastrocnemius PA was lower on the right (17.9±3.7° vs 20.5±3.7°; p=0.018, dz=−0.72). Peroneal PA differences were small (p=0.112).

MT showed a modest interaction (F(2,26)=3.69, p=0.039, ηp²=0.22). TA MT tended to be greater on the right and gastrocnemius MT lower, while peroneal MT was similar between limbs. CSA demonstrated no significant interaction (F(2,26)=1.87, p=0.174), with small paired differences across muscles.

For FL, a muscle main effect (F(2,26)=8.73, p=0.001) and a muscle×limb interaction (F(2,26)=5.24, p=0.012) were observed. TA FL was shorter on the right (42.9±3.4 mm) than the left (49.7±9.4 mm; p=0.016, dz=−0.74), whereas peroneal and gastrocnemius FL were comparable. Multivariate analysis showed limb separation only for the TA architecture vector (p=0.035); peroneal and gastrocnemius vectors were not significant. After FDR correction, TA PA remained the most robust effect.

Given the TA pennation and fascicle asymmetry with opposite-direction gastrocnemius changes, a limb×muscle interaction in %MVIC is anticipated, reflecting increased stabiliser demand on the limb with shorter TA fascicles and redistribution within the plantarflexors.
CONCLUSION:
Ballet dancers demonstrated a prominent between-limb TA architecture signature—greater pennation accompanied by shorter fascicles—despite broadly symmetric foot posture. Gastrocnemius exhibited smaller, opposite-direction pennation changes, while peroneal morphology was comparatively preserved. This multimodal profile supports targeted conditioning and monitoring focused on TA–peroneal–gastrocnemius force-sharing and frontal-plane stability demands in ballet.