Determination of selected punch parameters for professional boxers Birken L1, Morlock M1, Gross E2, Weltin U2 Biomechanics Section1, Mechanics Section2, Technical University Hamburg-Harburg Denickestrasse 15, 21073 Hamburg, Germany, www.tu-harburg.de/bim Introduction The effects of single or serial box punches are the topic of many publications, discussing anatomic, neurophysiologic and psychologic changes. Little, however, is known about mechanical parameters such as force, impact and acceleration during a single punch. The aim of this study was to determine mechanical parameters during the punch of professional boxers to estimate the traumatic potential. Materials and Methods The study was divided into two parts: (a) An experimental investigation of punches of two professional boxers (Vitalij and Wladimir Klitschko); the boxers performed single punches, using a boxing glove with an attached acceleration sensor and a standard punch bag (21kg) instrumented with an acceleration sensor (Figure 1). Figure 1: Experimental setup in the boxing gym. Left: The position of the 2 acceleration sensors is indicated. Right: Boxing punch of Vitalij Klitschko (instant after contact with the punch bag). (b) Experimental reproduction of punches in the laboratory with a pendulum impacting the same punch bag. A filled boxglove was accelerated at the end of a pendulum (6kg, ~ weight of the human arm and hand) to velocities as determined in part (a). A force sensor was mounted between the boxing glove and the pendulum. Additionally, tests with increased elasticity and increased mass of the punch bag were performed. Results The maximum velocity of the hand, derived from the measured acceleration was about 9.5m/s for either boxer (Fig. 3, 4). Acceleration of the hand was positive until contact with the bag attaining a maximum deceleration of 1420 re. 853m/s² for Vitalij / Wladimir. Contact time between bag and hand was about 20ms. The bag was accelerated to a velocity of 3.30 / 3.45m/s for Vitalij / Wladimir; maximum bag acceleration was 372 / 396m/s². The transmitted impulse was 196 / 203Ns. Reproduction of the punch in the laboratory showed a maximum force in the "wrist" of 5315 / 5545N. Force sensor Figure 2: Experimental setup in the laboratory. Top: instant just prior, during and after impact of the pendulum on the punch bag. Left: instrumented boxing glove with force and acceleration sensors indicated by arrows. Acceleration sensor 50 10 30 10 8 -30 -25 -20 -15 -10 -5-10 0 5 10 15 20 25 30 35 40 45 50 v bag -30 6 v hand Time [ms] Velocity [m/s] . -50 4 -70 -90 a hand [g] a bag [g] 2 -110 Acceleration [g] . Time [ms] -130 0 -150 -30 -20 -10 0 10 20 30 40 50 60 70 Figure 3: Single recordings for Vitalij Klitschko. Left: Accelerations of hand and punching bag. Right: Velocities of hand and punching bag. 50 10 30 10 8 -30 -25 -20 -15 -10 -5-10 0 5 10 15 20 25 30 35 40 45 50 v bag -30 6 Time [ms] v hand -50 4 -70 Velocity [m/s] ...... a bag [g] -90 a hand [g] 2 -110 Acceleration [g] . -130 Time [ms] 0 -150 -30 -20 -10 0 10 20 30 40 50 60 70 Figure 4: Single recordings for Wladimir Klitschko. Left: Accelerations of hand and punching bag. Right: Velocities of hand and punching bag. Increased elasticity of the contact area during experimental reproduction resulted in increased bag acceleration and velocity (+15%), the maximum wrist force decreased (-20%). Increased punch bag mass (+50%) resulted in decreased bag velocity and acceleration (-54%) and increased wrist force (+20%). Discussion The high observed forces indicate that a mechanical support of the wrist, as supplied by a boxing glove and especially the taping is required. The values recorded are comparable to values available in the literature (Atha et al., 1985). The small difference in the results between the normal punchbag and the bag with elastic contact zone showed, that the hit elasticity is mainly influenced by viscoelastic deformation of the glove. Assuming that the human head is more elastic than the punchbag and has a lower mass (~7kg), the increase in acceleration is about 80% when compared to a punch against the bag, yielding accelerations around 600m/s² (corresponding to forces around 3500N). In automotive accident research, these levels are seen as critical, even if only occuring for contact times of 20ms. References Atha, J., Yeadon, M.R., Sandover, J. and Parsons, K.C. The damaging punch. Br Med J (Clin Res Ed ) 1985 Dec 21 -28 291: 1756-1757..