Get on up: Relating objective hip-hop dance biomechanics to subjective scoring
Abstract
INTRODUCTION Hip-hop dance is a growing style of dance worldwide that typically involves an element of competition, where judges subjectively score dance performance1. To ensure competitive fairness, it is important to understand what judges are observing in dancers as part of the scoring process.2 Such research would help elucidate whether judges’ scores are more related to the objective biomechanics of dance moves, or other more subjective factors (e.g., attire). Therefore, the purpose of this study was to investigate the relationship between biomechanics of common dance moves among experienced dancers and how they are subjectively perceived by judges.
METHODS Eighteen experienced adult-aged dancers were recruited for this study. Participants learned a choreographed routine, which contained two specific dance moves that were used for analysis: the arm wave, where the joints and segments of the arm move in a wave-like pattern from left to right, and inverted happy feet, where the feet move in opposition from one another alternating in transverse plane rotation. A 12-camera 3D motion capture system was used to record the coordinates of 28 retro-reflective markers at 240Hz, two force plates recorded ground reaction force data, and a separate camera provided video of each choreographed trial. These recorded video trials were be sent off sent to three professional judges for scoring.
For the arm wave, marker coordinate data were used to calculate metrics related to the displacement and velocity of arm joints and segments, as well as the shape deviation of an arm wave move from a sinusoidal wave pattern.2 For the foot work, ground reaction force data were used to quantify the timing in forces between the two feet. Two stepwise linear regression models were then developed to test the degree to which: 1) arm wave kinematics and 2) foot work timing variables predicted judge’s scores.
RESULTS AND DISCUSSION Judges’ scores for the arm wave were significantly predicted (p < 0.001, adjusted R2 = 0805; Table 1) across all dancers by displacement of the right metacarpophalangeal (MCP) Joint (Figure 1; p < .05, 𝛃𝛃 = -.331), as well as propagation velocity of the left forearm (p < .05, 𝛃𝛃 = -.248) and right forearm (p < .05, 𝛃𝛃 = -.891). Judges’ scores for footwork were also significantly predicted by Timing Difference across all the dancers’ performance (p < . 05, 𝛃𝛃 = -.535). Figure 1 Right MCP Joint Displacement vs. Avg. Judges Scores.
CONCLUSIONS Judges seemed to only focus on the beginning of the arm wave and seemed to rely on speed of both forearms to potentially show mastery & control. Using Biomechanical Analysis, this may prove fruitful to study other styles of dance or different movements common across styles to provide more predictors for performance and to catalog dance styles within academic literature.
REFERENCES [1] Kojima et al., JMD, 6:1, 1- 11, 2018 [2] Sato et al., J. Appl. Biomech 31: 1, 1 – 7, 2015
Joshua Vicente
Adjunct Professor and Lab Alumni
Belle Pearl Ponce de Leon
Master’s Candidate
