Skill-level differences in a dynamic agility-stability trade-off in dance

This study examined how dancers of differing expertise coordinate joint-level variability to stabilise task-relevant controlled variables during a complex whole-body action. Twenty-nine adult Latin Ballroom dancers (beginners, intermediates, experts) performed 10 cycles of the Cha-Cha-Cha Alternate Basic at 100 bpm while whole-body kinematics were recorded. Forty-two joint angles were time-normalised and reduced to nine principal components representing low-dimensional coordination modes. Using these modes as elemental variables, uncontrolled manifold (UCM) analysis quantified the Fisher z-transformed synergy index (ΔV') for six controlled variables (left/right foot centre of mass [CoM], left/right hand CoM, head CoM, whole-body CoM) across the eight phases of the cycle. Linear mixed-effects modelling then tested how dancer skill, controlled variable, and cycle phase shaped performance. Synergy strength increased from beginners to intermediates and then plateaued in experts. ΔV' was consistently higher for the feet, head, and whole-body CoM than for the hands, indicating selective stabilisation of task-defining and balance-related variables. It also varied across the dance cycle: synergy strength was reduced during the most mechanically and coordinatively demanding phase, and higher during subsequent stabilising phases. This reduction in ΔV' was interpreted as a temporary relaxation of stabilisation that permits greater agility. Such temporal modulation of stability was most pronounced in experts. Overall, the findings suggest that expertise refines a shared low-dimensional coordination architecture by strengthening and temporally tuning performance-stabilising synergies, consistent with a dynamically managed agility-stability trade-off in a complex rhythmic whole-body skill.