Response to Letter to Editor: Biomechanical Analysis of Lower Limb in Bharatanatyam Dance Using Musculoskeletal Modeling

We are pleased that our manuscript[1] has generated interest and discussion within the scientific community. However, we respectfully wish to clarify several points regarding the methodological concerns raised.

The readers suggest that the lack of multiple trials limits our ability to assess kinematic and kinetic stability. However, our exploratory single-subject study design was explicitly stated and is methodologically appropriate for novel biomechanical investigations in underrepresented populations. Single-subject case studies examining new applications have established precedent in dance biomechanics literature and serve as necessary first steps before larger multiparticipant investigations. Similar single-subject approaches have been successfully employed.[2,3] The purpose of time normalization was to facilitate comparison of movement patterns across the three Paichal variations. Event-based normalization and reporting of intrasubject variability were beyond the scope of the study and could further strengthen future investigations. The decision to analyze the dominant limb was made to simplify the exploratory analysis and maintain consistency with several previous musculoskeletal modeling studies. We agree that bilateral analysis would provide additional insights and have identified this as an important direction for future work.

Regarding marker set validation, the Baker’s 36-marker set is a well-established and validated protocol in biomechanics research with extensive precedent. To our knowledge, no evidence suggests that this standard anatomical marker placement becomes invalid during dynamic or extreme joint positions. The markers follow anatomical landmarks consistently, regardless of joint configuration.

The reader notes that forces were not normalized to movement speed or jump height. Normalization to body weight is the standard practice in biomechanics and permits meaningful comparison across studies. Normalizing away movement speed and task intensity would obscure rather than clarify the true mechanical demands inherent to each movement variation.

The readers also note the use of descriptive terms such as “highest,” “substantially higher,” and “clear differences” in the absence of statistical testing. Since this was an exploratory single-subject biomechanical analysis, inferential statistical testing was neither appropriate nor intended. These terms were used descriptively to report the observed magnitudes within the analyzed dataset and should not be interpreted as population-level statistical inferences.

Regarding the single-degree-of-freedom knee model, we explicitly acknowledged this limitation in our discussion. We employed a previously validated and widely used musculoskeletal model. Incorporating additional degrees of freedom would require the development, calibration, and validation of an alternative model, which remains an active area of research in musculoskeletal modeling. All studies using the same model keep this limitation in mind. This simplification does not invalidate our findings but rather contextualizes them as estimates of knee loading within the constraints of our modeling approach.

Regarding the reported joint contact forces, the values presented in the manuscript represent model-estimated internal joint reaction forces obtained through musculoskeletal modeling and should not be interpreted as directly measured in vivo forces. Such estimates are influenced by model assumptions, scaling procedures, and muscle force predictions. The primary purpose of reporting these values was to compare the relative mechanical demands among the three Paichal variations within the same modeling framework. The comparison with the Irish dance study was intended only to provide context regarding the magnitude of internal loading reported in dance biomechanics literature and not to imply direct biomechanical equivalence between ankle and knee joint contact forces.

Finally, our linkage between biomechanical findings and injury risk was carefully connected to existing epidemiological survey data on Bharatanatyam dancers,[4] not presented as causal inference. The survey findings were cited to provide clinical context and demonstrate that the anatomical regions identified as highly loaded in our biomechanical analysis correspond to regions frequently reported as symptomatic in Bharatanatyam dancers. This integration of evidence levels is appropriate and strengthens clinical relevance.

We also acknowledge that broader statements regarding Bharatanatyam dancers as a population, contemporary physical conditioning, and possible modifications to traditional training practices should be interpreted within the exploratory nature of the study. These remarks were intended to stimulate discussion regarding dancer safety and future research directions rather than serve as definitive evidence-based recommendations.

We appreciate these constructive observations, which highlight important considerations for future studies involving larger cohorts, repeated-trial analyses, bilateral assessment, subject-specific modeling, and integration of electromyography. We believe such investigations will further strengthen the evidence base regarding biomechanics and injury prevention in Bharatanatyam dancers.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.