Chair Freeze, a Basic Posture in Breaking, Exerts Over 1.5 Times the Contact Pressure Concentrating on the Radial Half of the Palm Compared to Handstand.

Introduction: Excessive contact forces on the hands during breaking can potentially cause a high injury incidence. Chair freeze is a basic posture unique to breaking; however, its effect on the hands remains unclear. Clarifying dancer-specific factors is essential for preventing trauma and overuse injuries. This study aimed to investigate the contact load and pressure on the hands during chair freeze and their determinants.

Methods: 15 professional breakers were recruited. The peak landed load per bodyweight and contact pressure were measured using thin-film pressure sensors in the chair freeze and handstand postures. The location of the highest pressure was also assessed. The following possible factors of load and pressure were assessed: age, height, weight, body mass index, hand axis, practice duration, and grip strength.

Results: Load per bodyweight and pressure were significantly higher in the chair freeze than in the handstand (0.69 bodyweight vs 0.47 bodyweight and 247.1 kPa vs 155.8 kPa; P < .0001 and P < .0001, respectively). In 14 of 15 dancers (93.3%), the highest pressure was concentrated on the radial side of the palm during chair freeze. Body height and weight were significantly correlated with load per bodyweight and pressure in chair freeze (ρ = 0.55, 0.57, 0.54, and 0.59; P = .036, .028, .038, and .020, respectively).

Conclusion: Load per bodyweight and pressure on the landed hand was 1.5- to 1.6-fold higher during the chair freeze than during the handstand, concentrating on the radial side of the palm. Dancers' body size was associated with the contact force on the hand in the chair freeze.