Tibialis posterior strength and lower extremity kinematics in Kathak dancers with pronated feet: A biomechanical analysis

Kathak is an ancient form of Indian classical dance and arose from Kathaks, or storytellers, of North India. Kathaks narrate their tales through facial and eye expressions, rhythmic hand gestures, and foot movements. The three main elements of Kathak are Nritta (pure dance), Nritya (expressive), and Natya (dramatic elements). Dancers use ankle bells called Ghungroos while performing the dance, which includes spinning movements of the foot (chakkars). It gives rhythm to their performance (Chatterjee et al., 2013). The existence of ankle bells (Ghungroos), which weigh around 1.5 kg on each side, increases the foot’s discomfort. Repeated use of these ankle bells results in tendon strain and other connective tissue damage during performance, leading to muscular imbalance (Chatterjee et al., 2013).

“Chari Bheda” is one of the indispensable portions of the Kathak, representing the formation of numerous types of foot movements presented while dancing. Footwork in Kathak dance involves repeated rapid foot stamping over the floor. They must perform various contorted bodily movements at a high rate, ranging from 1 to 108. This may expose the foot to a greater amount of stress, which leads to significant biomechanical changes (Chatterjee et al., 2013).

Kathak dance is known for its intricate footwork and rhythmic precision; its biomechanical demands may contribute to both adaptive and maladaptive musculoskeletal outcomes. The recent work by Oliva et al. (2023) underscores the role of exercise in modulating movement pattern–related disorders, offering a valuable framework for interpreting the neuromuscular adaptations seen in dancers. Integrating this perspective from dance medicine can enhance our understanding of how repetitive, culturally embedded movement practices shape musculoskeletal health.

Footwork in Kathak dance reduces the summit point of the medial longitudinal arch of the foot. As a result, the foot develops deformations such as overpronation over time. Sabharwal et al. (2017) state that more than 90% of the Kathak dancers developed pronated feet. The typical starting position of Kathak dancers during performance includes excessively externally rotated feet. The forefeet are positioned outward of the foot axis, putting excessive pressure on the medial foot. This typically results in a hyperpronated foot. Dancers often adopt this inappropriate posture during periods of nonpractice as well. This makes the foot prone to deformation. Furthermore, the performance over hardened floors increases the effect of the ground reaction force on the foot during stamping (Simmel et al., 2013).

Overstamping the foot causes excessive load on the intrinsic muscles and foot inverters, ultimately resulting in the flattening of the medial longitudinal arch, which eventually leads to foot pronation. The medial longitudinal arch flattening results in a displacement of the talus. This alters the axis of the Talocalcaneal joint to below 45° in the anteroposterior direction. This results in significant pronation of the foot, accompanied by considerable eversion and valgus deformity in the rear foot. This may also disrupt the other tarsal bones, thereby resulting in severe foot pronation (Simmel et al., 2013).

In individuals with pronated feet, characterized by a flattened arch and excessive inward rolling of the foot, the tibialis posterior tendon often becomes overworked. This increased demand can lead to tendon fatigue and dysfunction and, over time, contribute to the development of adult-acquired flatfoot deformity (Koura et al., 2017). The FPI-6 was developed as a diagnostic tool in various ways. It can be used to determine biomechanical risk factors for certain issues, investigate the relationship between foot type and certain risk factors, identify foot type and patient classification for therapeutic purposes, and assess differences in the foot structure (Aquino et al., 2018).

An assessment of muscle strength is typically performed as part of a patient’s objective assessment. It is used to evaluate weakness and can be effective in differentiating true weakness from imbalance or poor endurance. It may be referred to as motor testing, muscle strength grading, or manual muscle testing (Naqvi et al., 2019). GaitON is a two-dimensional software suitable for analysis due to its lower cost compared to three-dimensional motion capture systems, which require minimal equipment, consisting of only a high-speed camera and software. Optimal for clinics, small research laboratories, and field evaluations where financial constraints and spatial limitations exist. It facilitates a more accessible approach to the participants. It offers valuable insights when utilized appropriately (Michelini et al., 2020).

The GaitON system features numerous adjustable settings, making it an ideal tool for both clinical and research applications. It provides extensive evaluation modules, encompassing both static and dynamic assessments, including gait analysis. The adaptable video input accommodates analysis with multiple camera types, ranging from mobile devices to advanced digital cameras, guaranteeing versatility for various research configurations. It also encompasses efficient data processing modules that substantially decrease analysis time and produce structured reports with normative values for straightforward interpretation. Additionally, it supplies all computed data and reference values in Excel format, facilitating data organization and subsequent analysis. It also offers a comprehensive examination of gait metrics, facilitating a profound understanding of gait mechanics (Alam et al., 2024).

Therefore, the aim of the study is to investigate the correlation between foot pronation and tibialis posterior muscle strength in Kathak dancers and to explore the relationship between foot pronation and lower extremity kinematics during gait in Kathak dancers. It is essential to educate Kathak dancers regarding possible biomechanical changes in the lower extremities resulting from extended dance practice, as well as to underscore the significance of early evaluation and intervention to avert musculoskeletal issues associated with pronated foot posture in Kathak dancers.

The data of foot posture index, tibialis posterior muscle strength, and lower extremity kinematics of Kathak dancers were tabulated, and the Pearson correlation coefficient was calculated. One-sample t-test was employed to determine the difference between normative values and the mean values of kathak dancers. The data analysis was done by using IBM SPSS version 25.

Table 2 shows the mean value of FPI score (7.80 and 7.40 for left and right foot, respectively) and tibialis posterior muscle strength (3.83 and 3.79 for left and right foot, respectively). R value for correlation between FPI score and tibialis posterior muscle strength in Kathak dancers with pronated foot occurred nonsignificant as p > 0.05.

Table 3 shows the mean value of the FPI score and variables related to sagittal plane kinematics of the ankle joint during each event of the gait cycle. There is no significant correlation between FPI and sagittal plane Ankle joint kinematics during all the events of the gait cycle on both feet, as p > 0.05, except for initial contact and mid swing of the right side

Table 4 shows the mean value of the FPI score and variables describing a sagittal plane kinematics of the knee joint during each event of the gait cycle. There is a significant positive correlation between FPI score and knee joint kinematics during initial contact, loading response, mid-stance, and terminal stance on the right side and initial contact and mid-stance of the left side, as p < 0.05. There is no significant correlation between FPI and all other events of the gait cycle on both sides, as p > 0.05.

Table 5 shows the mean value of FPI score and sagittal plane kinematics variables of hip joint during each events of gait cycle. R value for correlation between FPI score and variable-related hip joint kinematics during initial contact, loading response, mid-stance, terminal stance, pre swing, initial swing, and mid swing are presented.

There is a significant negative correlation between FPI score and hip joint kinematics during loading response and mid-stance of both side and initial contact, terminal stance and pre swing of right side as p < 0.05. There is no significant correlation between FPI and hip joint kinematics during initial swing and mid swing on both sides as p > 0.05. There is no significant correlation between FPI and hip joint kinematics during initial contact, terminal stance, pre swing of left side as p > 0.05.

Table 6 shows the mean value of the FPI score and variables related to frontal plane kinematics of the rear foot, knee, and pelvis during mid-stance of gait.

There is a significant positive correlation between FPI score and rear foot angle during mid-stance on both feet. There is no significant correlation between FPI score and knee adduction/abduction during mid-stance on both feet. There is no significant correlation between FPI score and pelvic drop during mid-stance on both feet.

Table 7 shows a comparison between the mean of lower extremity kinematics of kathak dancers and normative values using one-sample t-tests. Ankle joint kinematics of Kathak dancers has a significant difference when compared with normative values in initial contact, loading response, terminal stance, initial swing, mid swing on both side and also in mid-stance of left side as p < 0.05. There is no significant difference between ankle joint kinematics of Kathak dancers and normative values in pre swing phase of both side and mid-stance of the right side as p > 0.05. Knee joint kinematics of Kathak dancers has a significant difference when compared with normative values in initial contact, pre swing and mid swing on both sides and also in loading response and mid-stance of the right side as p < 0.05.

There is no significant difference between knee joint kinematics of Kathak dancers and normative values in terminal stance, initial swing phase of both side and in loading response, and mid-stance of left side as p > 0.05. Hip joint kinematics of Kathak dancers has a significant difference when compared with normative values in all events of gait cycle as p < 0.05.

There is a significant difference between mid-stance rear foot angle of Kathak dancers and normative values on both sides as p < 0.05. There is no significant difference between mid-stance pelvic drop of Kathak dancers and normative values on both sides as p > 0.05. There is a significant difference between mid-stance knee adduction of Kathak dancers and normative values on both side as p < 0.05.

This table demonstrates how Kathak dancers differ from the established normative gait kinematics across ankle, knee, and hip movements. Significant positive or negative mean differences (Δ), supported by confidence intervals and moderate-to-large effect sizes, indicate distinct biomechanical adaptations linked to dance training. In contrast, angles with small or clinically negligible effect sizes – despite statistical significance – represent minor deviations unlikely to reflect functional limitation.

The objective of this study is to investigate the relationship between foot pronation and tibialis posterior muscle strength, as well as the impact of pronated foot posture on lower limb kinematics during gait in Kathak dancers. Our findings indicate no significant correlation between FPI scores and tibialis posterior muscle strength among the participants. This suggests that while pronation and hyperpronation are prevalent in Kathak dancers, these postural deviations do not necessarily compromise the strength of the tibialis posterior muscle.

Even though statistically not significant, clinically, there is a mild to moderate reduction in the strength of the tibialis posterior muscle, which, in turn, over a long period of time, may lead to functional collapse of the arch, musculoskeletal pain, and balance issues, and eventually lead to pronation since long-term observation may necessitate the problems.

The absence of a significant relationship between FPI scores and tibialis posterior strength aligns with the findings of Neville et al. (2010), who reported that flatfoot deformity can occur without corresponding deficits in tibialis posterior muscle strength. Conversely, our results contrast with those of Alam et al. (2019), who demonstrated that tibialis posterior strengthening exercises improved navicular drop, muscle activity, and dynamic balance in individuals with flat feet. This discrepancy may be attributed to differences in study populations, methodologies, or the specific demands placed on the foot musculature in Kathak dancers. Migliorini et al., (2023) findings support the argument that tibialis posterior strength and FPI scores are clinically meaningful in assessing injury risk and performance capacity. This also aligns with the broader goal of dance medicine: optimizing movement efficiency while minimizing biomechanical strain.

The unique demands of Kathak dance, characterized by continuous contact of the medial foot with the floor and the use of heavy ankle bells (ghungroos), may contribute to the functional flatfoot over time (Sabharwal et al., 2017). This repetitive stress could lead to elongation of the tibialis posterior tendon and a subsequent decrease in the height of the medial longitudinal arch, resulting in pronation and hyperpronation during weight-bearing activities. However, the maintained strength of the tibialis posterior muscle suggests a complex interplay between structural adaptations and muscular function in this population.

D’Elia’s (2023) work on physical education and movement adaptation emphasizes that specialized training environments foster unique motor patterns and muscular adaptations. Repetitive, skill-specific movement – such as the rhythmic stamping and postural control in Kathak – can lead to targeted strengthening of muscles like the tibialis posterior. Motor learning and proprioceptive feedback in structured training settings may override structural deviations, allowing for functional resilience.

In terms of lower limb kinematics, our study found that increased foot pronation is associated with greater plantarflexion at the ankle during initial contact, increased knee extension during loading response and mid-stance, and reduced hip flexion and extension during various phases of gait. These findings are consistent with those of Marouvo et al. (2021), who reported reduced ankle dorsiflexion and hip flexion/extension in individuals with flatfoot. However, our observations regarding knee kinematics differ from Marouvo et al.’s (2021) findings of reduced peak knee extension in flatfooted subjects. These variations may reflect compensatory mechanisms employed by Kathak dancers to absorb stress forces not mitigated at the foot level.

Furthermore, our analysis revealed a positive correlation between foot pronation and rear foot eversion angles during mid-stance, with significantly increased rear foot eversion observed bilaterally. This supports the findings of Buldt et al. (2015), who reported a connection between increased pronated foot posture and elevated rear foot peak eversion during the stance phase of gait. Interestingly, foot pronation did not significantly affect knee adduction/abduction movements or pelvic drop during mid-stance; an increase in knee adduction during mid-stance was noted bilaterally when compared to normative values (Buldt et al., 2015). The lack of correlation may reflect adaptive dissociation between foot and knee mechanics in trained dancers. Hraste et al. (2023) framework supports the idea that movement efficiency can be maintained through alternative joint strategies, even when distal alignment is altered. This reinforces the need to assess whole-body coordination, not just isolated joint relationships.

Russo et al. (2020) explored how foot mechanics influence motor control and gait variability, emphasizing the role of rhythmic lower limb coordination in stabilizing movement. Foot-ground interaction affects the entire kinetic chain, influencing joint angles, muscle activation patterns, and postural control. Altered foot posture can lead to increased variability in gait cycles, which may compromise stability and increase injury risk.

Like rhythmic gymnasts, Kathak dancers undergo rigorous, repetitive training that may foster adaptive resilience in the face of structural deviations. The maintenance of tibialis posterior strength and nonlinear joint compensation patterns observed in our study could reflect performance-driven adaptations, rather than dysfunction. Esposito et al.’s (2024) findings support a broader view of biomechanical plasticity, where competitive or performance-based training leads to functional adaptations that differ from general population norms.

This study acknowledges several limitations that may influence the generalizability and depth of its findings. First, the number of hours of weekly practice among participants was not considered, which could affect the degree of foot pronation and muscle strength adaptations. Second, the study exclusively included female Kathak dancers, omitting potential gender-based biomechanical variations. Finally, participants were recruited solely from a single locality, limiting the diversity of training backgrounds and regional dance styles. The FPI represents a static assessment, while gait kinematics reflect dynamic movement. This difference limits the direct comparability of the two measures and should be considered when interpreting correlation results.

To enhance future research, it is recommended to broaden the study to encompass a larger and more diverse population of Kathak dancers across various Indian states, including male dancers, to capture a broader spectrum of biomechanical adaptations. Future studies should include male dancers to understand potential gender-based biomechanical differences. Employing more reliable and validated measures (instruments like dynamometry) can improve the assessment of tibialis posterior muscle strength. In addition, comparing the tibialis posterior muscle length between dancers with pronated feet and those with neutral foot posture could provide deeper insights into structural adaptations associated with prolonged dance practice. A follow-up study incorporating an appropriate control group and detailed documentation of training variables (such as frequency, intensity, duration, and specific training components) is recommended to strengthen the validity of these preliminary findings and allow for more robust comparisons across participant groups. Implementing these recommendations will contribute to a more comprehensive understanding of the impact of Kathak dance on lower extremity biomechanics.

Finally, our study found that FPI scores were not significantly influenced by age or years of Kathak practice, suggesting that factors such as daily practice duration and consistency may play a more critical role in the development of foot postural deviations.

This study concludes that the tibialis posterior muscle may exhibit a mild decrease in strength. But significant changes in lower limb kinematics are associated with many factors, particularly affecting gait parameters in the frontal plane more than in the sagittal plane. These adaptations may increase injury risk and impact performance efficiency. The FPI represents a static standing measure while gait kinematics reflect dynamic movement; hence, the study was interpreted with caution. Future research should focus on targeted interventions, including intrinsic foot muscle strengthening, to mitigate these changes and enhance the musculoskeletal health and longevity of Kathak dancers.

The authors would like to acknowledge the management of SRM Institute of Science and Technology for granting permission and support to conduct this study. The authors also extend their sincere gratitude to all the participants for their cooperation.

The authors gratefully acknowledge the financial support provided by the SRM College of Physiotherapy, Faculty of Medicine and Health Sciences, SRM Institute of Science and Technology (SRMIST), Kattankulathur, for bearing the publication-related costs of this article. The funding body had no role in the design of the study, data collection, analysis, interpretation of data, or writing of the manuscript.

In terms of the research’s conception or design, data collection, analysis, or interpretation, and writing or critical review for pertinent intellectual content, the authors stated that they had significantly contributed to the work. All authors agreed to accept public responsibility for every facet of the study and gave their approval for the final version to be published.

No financial, legal, or political conflicts involving third parties (government, private companies, and foundations, etc.) were declared for any aspect of the submitted work.