Foot Pressure Mapping in Bharatanatyam Dancers and Age and Gender Matched Non-Dancers

Introduction

Bharatanatyam is one of the famous and oldest classical dance forms of Southern India, which originated in Tamil Nadu.¹ Bharatanatyam is a combination of several movements which comprises the rhythmic tapping of the feet by adapting different postures of the body. It can be considered as an amalgamation of repetitive foot, hand movements with different facial expressions.² There are various styles of Bharatanatyam namely, Pandanallur style, Vazhuvoor style, Kalakshetra style, Melattur style, Kalamandalam style. Feet can be considered as primary component in this dance form because of their constant interaction with the ground. Bharatanatyam dancers are more prone to foot problems and injuries, since their feet are continuously exposed to forces which can result in instability and postural deviations.³ It is crucial to evaluate the alterations in foot pressure and focus on the preventive measures for averting the foot and lower extremity injuries. The pressure which acts between the foot and the supporting surface during every day locomotion is called foot pressure.^3,4 In foot pressure mapping, the pressure distribution on an individual’s feet is measured and analyzed, which gives a brief description pertaining to the ground reaction forces.⁵

Identification and quantification of areas of high pressure can be done by foot pressure mapping which can diagnose the foot problems at an early stage and helps in implementing the preventive measures.⁵ This study focused on foot pressure mapping among Bharatanatyam dancers and age and gender-matched non-dancers using Harris Mat. Foot pressure mapping systems are of mainly two types, Pressure distribution platforms (includes Harris mat and Pressure stat) and In-shoe systems.⁶ Harris mat is used as a tool in the bare foot evaluation to obtain the geographical loading of the foot and to measure the plantar pressure.⁷ Harris mat can measure plantar pressure between 0.27 Kg/cm² and 4.80 Kg/cm² . 7 Thus it aids in the identification of those individuals who have high foot pressure points. High foot pressure is indicated as darkened area. It has a sensitivity of 0.57 and specificity of 0.77. Harris mat has good reliability.7 The Harris mat technique has an inter observer reliability of 0.81 to 0.96. The application is easy and plantar pressure can be assessed at low cost. One can rely on Harris mat for mapping the foot pressure and for analyzing the abnormal plantar pressure.^7,8

Materials and Methods

Based on the evidence that was provided and the recommendations for conducting an observational study, the sample size estimation was carried out. Convenience sampling was used to select the subjects for the study. The sample size computation was carried out using the G power 3.0.10 software. The input parameters were as follows: α error was 0.05, power (1-β error) was 0.8, effect size was 0.3. Number of predictors used were 2. By using this formula, total sample size was calculated. The total sample size was 82. This comprised 41 Bharatanatyam dancers and 41 age and gender matched non-dancers.

Individuals from both the genders, Bharatanatyam dancers aged 12 years and above who have been practicing weekly thrice for six months or more, were only considered for the study. Non-dancers with same BMI were included in the study.³

Individuals with congenital or acquired deformities of lower limbs, musculoskeletal injuries in the past six months, recent surgeries involving lower extremities, history of any neurological involvement and subjects with unilateral or bilateral flat foot were excluded from the study.³

Harris mat was used as an outcome measure in the study. The materials used in the study were, Harris mat, recording paper, ink bottles, ink pad and ink roller.

Bharatanatyam dancers were recruited from various schools of Bharatanatyam in Mysuru city. Non-dancers of same age and gender were sought for from numerous schools in Mysuru city. Written informed consent was obtained from recruited participants. The study protocol and consent form were reviewed and approved by the IEC of JSS Medical College prior to commencement of the study (JSSMC/IEC/05012022/03NCT/22021-22). A pilot study was conducted including five Bharatanatyam dancers and five non-dancers to standardize the protocol. Later, forty-one Bharatanatyam dancers and forty-one non-dancers were recruited. Demographic data of each participant was collected. A familiarization process of foot pressure assessment was performed for all the participants before the commencement of data collection.

A screening form was given to document the demographic data, frequency of Bharatanatyam practice sessions, number of hours of practice, discomfort experienced by the Bharatanatyam dancers during and/ or after the practice (if any), type of footwear used by the dancer on a daily basis and involvement of dancers in any other sports activities (if any). After obtaining the responses, data was collected from the respondents. Among 41 Bharatanatyam dancers recruited, only thirty were eligible to participate in the study given the number of practice sessions per week.

Subject preparation

The procedure and the objectives of the study were explained to the subjects in their vernacular language. Consent form was given to the subjects and written consent was obtained from the subjects after explaining the procedure.

Before testing, the subjects were instructed to walk across a walk way. This acted as a warm up and helped the subjects not to consciously walk on the Harris mat during testing. The subjects were made familiar to the procedure. No shoes were allowed to be worn during the procedure as it was a bare-foot plantar pressure analysis.

Study setup and procedure

The ink was rolled evenly over the ink pad with the help of ink roller. Once sufficient amount of ink was applied to the ink roller, the ink roller was used to evenly spread the ink over the Harris mat. Recording paper was placed above the layer of ink applied within the Harris mat.⁷

Procedure for obtaining footprint

The subjects were instructed to step on the Harris mat while maintaining a normal walking speed. The subjects were encouraged to walk on the Harris mat without being conscious about their gait pattern. The foot prints of both the feet were recorded in the stance phase of the gait. The underlying paper recorded the foot pressure of the subject accordingly.⁷

Analysis of foot prints obtained from Harris Mat

The data were analyzed by description analysis. High foot pressure was indicated as darkened area, moderate foot pressure as grayish area and low foot pressure was indicated as lightened area. The outline of the foot was drawn by direct tracing. The foot was divided into five weight bearing regions: Hallux, lesser toes, metatarsal heads, mid foot and hind foot.⁸ The pressure points were analyzed in these five weight bearing regions of the foot and were analyzed for high, moderate and low pressures depending upon the darkened, grayish and lightened areas, respectively.⁸ The areas of high pressure points were analyzed using Sketch and Calc software (Dobbs, Elliott M. “www.SketchAndCalc.com.” Sketch and Calc. Elliott M Dobbs, 20 Feb. 2011.Web). The footprint images were scanned using a scanner application. The scanned foot print images were uploaded to the Sketch and Calc software. Areas of high pressure points were highlighted using suitable shapes in the software, following which the application provided the calculated area of high-pressure points. The software can calculate irregular areas of high pressure points in the foot. Hence, a quantifiable value of the area of high pressure points in the weight-bearing regions of the foot was obtained.

The obtained high pressure points of weight bearing regions of foot were entered in the Excel spreadsheet. Jamovi 2.3.17 software was used for data analysis.

Results

The mode and median were calculated and non-parametric test of comparison, Mann-Whitney U was used to compare the foot pressure changes between dancers and non-dancers, since the data was in the ordinal scale. P ≤0.05 was considered significant.

Discussion

The present study titled “Foot pressure mapping in Bharatanatyam dancers and age and gender matched non-dancers” was conducted to map the foot pressure and to analyze the foot pressure differences between Bharatanatyam dancers and age and gender matched non-dancers using Harris mat as an outcome measure. The mean age of dancers and non-dancers included in the study was 15.4±3.61 years. The BMI of the dancers and non-dancers participating in the study was 19.3±3.21 and 18.4±3.10 years, respectively.

The current study revealed significant foot pressure changes among Bharatanatyam dancers compared to age and gender matched non-dancers. An increased foot pressure was observed at the bilateral Hallux with the significance of P=0.04 and P=0.00 at right and left, respectively among dancers. Similar findings were observed in a study conducted by S. Nair et al. (2018) titled, “The survey of musculoskeletal disorders among Bharatanatyam dancers in Mumbai and Mangalore”. This study revealed an increase in pressure at the Hallux attributable to Bhramari, which entails high-impact jumping activities in which dancers land on their toes.⁹

An increased foot pressure was observed among dancers at the left hind foot (P=0.035). This is in agreement with the findings of a study conducted in 2022 by R. Mullerpatan et al. evaluating the differences in foot characteristics between Bharatanatyam dancers and age-matched non-dancers. It was reported that total peak plantar pressure was 37% higher among dancers compared to non-dancers of the same gender and indicated a higher plantar loading during walking.¹⁰

An increase in the foot pressure at the Hallux and the hind foot can be potentially attributed to Kuditta Mettadavu which is frequently performed by the Bharatanatyam dancers. It is one of the only adavus in Bharatanatyam which assumes a very static position. Kuditta mettadavu can potentially result in an increase in the pressure at the Hallux and the hind foot, since it involves jumping on the ball of the toes followed by heel striking. Kunchita pada (The heel off and toes bent down position) can potentially exert increased pressure at the Hallux. On the other hand, Nattadavu (heel striking by stretching the legs) and Anchita pada (the heel contact position with forefoot and toe raised) can potentially exert an increased pressure at the hind foot when performed in medium and high speed. In this study, both right and left feet were considered as independent contributors.¹¹

As far as the non-dancer population is concerned, on a daily basis, there is no much of repetitive tapping movements involved which do not yield in pressure alterations of the foot provided the latter is not involved in any athletic or gymnastic activities.

The current study revealed a reduced plantar pressure at the mid foot among dancers compared to any other weight bearing regions of the foot. This could be because Bharatanatyam dancers start dancing from young age, the arches are better developed reducing the pressure on the mid foot.

Therefore, it is very crucial to follow proper dance techniques during practice to avoid complications which can potentially occur in future by following improper techniques.

Conclusion

An increase in the foot pressure was observed at the bilateral Hallux and left hind foot of Bharatanatyam dancers compared to age and gender matched non-dancers. This can potentially lead to Hallux limitus (the big toe joint becomes stiff and often painful with movement), Hallux valgus, plantar fasciitis or Achilles tendinopathy. Foot wear modification in dancers as they age must be considered. Correct technique is crucial for dancers because using improper technique repeatedly can lead to overuse injuries and biomechanical changes in the foot, such as high foot pressure over weight-bearing areas of the foot. Preventive measures like early intervention and treatment must be adapted to prevent the complications which can potentially occur in the long run.

Declarations

Ethics approval and consent to participate

The project “Foot pressure mapping in Bharatanatyam dancers and age and gender matched non-dancers” has been cleared and approved by the Institutional Ethical Committee of JSS Medical College, JSSAHER, formerly and JSS University, with reference no JSSMC/ IEC/05012022/03NCT/22021-22.

Competing interests

The author(s) declare(s) that they have no competing Interests.

Funding & Acknowledgements

This study is a part of the main study funded by Rajiv Gandhi University of Health Sciences, Bengaluru, India, under project code UG21PHY345.

Conflict of interest

None