Available online at www.sciencedirect.com Journal of Science and Medicine in Sport 14 (2011) 547–552 Original research An investigation of shoulder forces in active shoulder tackles in rugby union football Juliana Usman a,b , Andrew S. McIntosh a,∗ , Bertrand Fréchède a a Risk and Safety Sciences, University of New South Wales, 2052 Sydney, Australia b Department of Biomedical Engineering, University of Malaya, Malaysia Received 3 December 2010; received in revised form 29 April 2011; accepted 19 May 2011 Abstract In rugby union football the tackle is the most frequently executed skill and one most associated with injury, including shoulder injury to the tackler. Despite the importance of the tackle, little is known about the magnitude of shoulder forces in the tackle and influencing factors. The objectives of the study were to measure the shoulder force in the tackle, as well as the effects of shoulder padding, skill level, side of body, player size, and experimental setting on shoulder force. Experiments were conducted in laboratory and field settings using a repeated measures design. Thirty-five participants were recruited to the laboratory and 98 to the field setting. All were male aged over 18 years with rugby experience. The maximum force applied to the shoulder in an active shoulder tackle was measured with a custom built forceplate incorporated into a 45 kg tackle bag. The overall average maximum shoulder force was 1660 N in the laboratory and 1997 N in the field. This difference was significant. The shoulder force for tackling without shoulder pads was 1684 N compared to 1635 N with shoulder pads. There was no difference between the shoulder forces on the dominant and non-dominant sides. Shoulder force reduced with tackle repetition. No relationship was observed between player skill level and size. A substantial force can be applied to the shoulder and to an opponent in the tackle. This force is within the shoulder’s injury tolerance range and is unaffected by shoulder pads. © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. Keywords: The tackle; Rugby union football; Biomechanics; The shoulder; Shoulder pads 1. Introduction In rugby union football the tackle is an important and fre- quently executed contact skill in which the tackler attempts to engage and hold the ball carrier and bring the ball carrier to the ground. McIntosh et al. observed an average rate of 146.0 tackles per hour in non-professional levels and the tackle rates in professional rugby were reported to be between 142.0 and 166.0 tackles per hour. 1–3 An important tackle technique is the ‘active shoulder tackle’ in which the tackler’s shoulder is the first point of contact with the ball carrier, and the tackler uses leg drive and momentum to execute the tackle. 1 McIn- tosh et al. identified nearly 23% of the 6618 tackles assessed as active shoulder tackles, as well as an association between ∗ Corresponding author. E-mail address: a.mcintosh@unsw.edu.au (A.S. McIntosh). level of play and tackle technique where the proportion of active shoulder tackles increased with level of play. 1 To date, a comprehensive biomechanical assessment of shoulder forces in the tackle and influencing factors, e.g. experience, Body Mass Index (BMI), side of body and shoul- der pads, has not been reported. In an active shoulder tackle the shoulder force vector (line of action and magnitude) will play an important role in determining whether the ball carrier is knocked backwards, lifted, for example, or the tackler is knocked backwards by the ball carrier. The magnitude of the shoulder force is not known. In a study limited to six rugby players and using a shoulder surface mounted Tekscan TM F- socket 9811 force sensor, Pain et al. reported the maximum impact force for rugby tackles without pads from a crouch position was 819 N and from a run-up was 1283 N. 5 In addition to being an important skill, the tackle has been identified as the game event in rugby union football most associated with injury, with 35–60% of injuries resulting 1440-2440/$ – see front matter © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jsams.2011.05.006