3 Original Article Lester Mayers, M.D., is in the Division of Sports Medicine, Pace University, Pleasantville, New York. Shaw Bronner, P.T., Ph.D., O.C.S., Sujani Agraharasamakulam, M.S., and Sheyi Ojofeitimi, M.P.T., are in the Analysis of Dance and Movement (ADAM) Center, Long Island University, Brooklyn, New York. Correspondence: Lester Mayers, M.D., Director of Sports Medicine, Pace University, 861 Bedford Road - Goldstein Fitness Center, Pleasantville, New York 10570; lmayers@pace.edu. Abstract Tap dance is a unique performing art utilizing the lower extremities as percus- sion instruments. In a previous study these authors reported decreased injury prevalence among tap dancers compared to other dance and sports participants. No biomechanical analyses of tap dance exist to explain this finding. e purpose of the current pilot study was to provide a preliminary overview of normative peak kinetic and kinematic data, based on the hypothesis that tap dance gen- erates relatively low ground reaction forces and joint forces and moments. Six professional tap dancers performed four common tap dance sequences that produced data captured by the use of a force platform and a five-camera mo- tion analysis system. e mean vertical ground reaction force for all sequences was found to be 2.06 ± 0.55 BW. Mean peak sagittal, frontal, and transverse plane joint moments (hip, knee, and ankle) ranged from 0.07 to 2.62 N∙m/ kg. ese small ground reaction forces and joint forces and moments support our hypothesis, and may explain the relatively low injury incidence in tap dancers. Nevertheless, the analysis is highly complex, and other factors re- main to be studied and clarified. I njuries occur frequently in ballet and modern dance, 1-9 with inci- dence and prevalence similar to that found in inter-collegiate sports 10 and high risk occupations. 11 Reported ballet and modern dance injury rates range from 0.62 to 18.3/1000 hours of exposure. The existing research strongly indicates that dance injuries predominantly involve the lower extremity and lumbar spine, and are mainly the result of cumulative mi- crotrauma (overuse). In a previous retrospective survey of experienced tap dancers we found a relatively low injury prevalence and occurrence rate (0.31/1000 exposures) among the cohort. 12 No biomechani- cal analyses of tap dance were available at that time to explain this finding, nor have any appeared since. Inter- estingly, studies of the dance styles that are most similar to tap (due to emphasis on percussive footwork), fla- menco 13 and Irish dance, 14 are equally devoid of such analysis. e purpose of the current study was to provide normative kinetic and kinematic data to explain our previous findings. We conducted a descriptive pilot study of common tap dance sequences based on the hypothesis that tap dancers are relatively free of injury because their art form generates low peak ground reaction forces and joint forces and moments. Methods Participants Six professional tap dance performers (3 males and 3 females) volunteered to participate in this study. Each subject was currently employed as a tap dance performer or teacher and was between the ages of 18 and 50. Criteria for ex- clusion included any musculoskeletal injury in the previous six months that caused the dancer to miss dancing for one or more weeks. e subjects mean age was 24.5 ± 10.6 years, and they had 14.0 ± 7.3 years of tap dance experience (Table 1). Each subject gave informed written consent in accordance with University Internal Review Board guidelines. A power analysis (power 0.80) using pilot data to calculate one and two-tailed test sample size determined that six subjects were sufficient for the study. 15 Experimental Protocol Four commonly performed tap dance sequences were selected for study: flaps, cramprolls, pullbacks, and one self-selected sequence considered by the subject to be technically demand- ing. Flaps are performed by alternating the feet brushing forward and down Lower Extremity Kinetics in Tap Dance Lester Mayers, M.D., Shaw Bronner, P.T., Ph.D., O.C.S., Sujani Agraharasamakulam, M.S., and Sheyi Ojofeitimi, M.P.T.