ORIGINAL ARTICLE Does cheating pay: the role of externally supplied momentum on muscular force in resistance exercise Ognjen Arandjelovic ´ Received: 6 April 2012 / Accepted: 3 May 2012 Ó Springer-Verlag 2012 Abstract Our work investigates the use of ‘‘external momentum’’ in the context of hypertrophy-oriented train- ing. This is momentum supplied to the load (such as a dumbbell) used in an exercise by means of action of muscles not inherently involved in the exercise. We chal- lenge the general consensus that the use of such momentum often described as ‘‘cheating’’ is counterproductive. We focus on the use of external momentum in the shoulder lateral raise and adopt a framework whereby exercise execution is simulated on a computer. This is achieved using a physical model of motion which is combined with anthropomorphic measurements and empirical data of muscular recruitment from previous work. The introduc- tion of moderate momentum (producing initial angular velocities around 57.5° s -1 ) increases the torque of the target muscles even without an increase in the load used. A moderate increase in the load and the use of momentum allows the torque to be increased even further. In contrast, excessive use of momentum results in lower demands on the target muscles, while an excessive increase of the load reduces the total hypertrophy stimulus by virtue of the decreased number of repetitions which can be performed successfully and thus the dramatically shortened time under tension. Our results disprove the conventional belief that the use of external momentum necessarily reduces the overload of the target muscles. A moderate use of external momentum increases both the per-repetition peak torque and the total hypertrophy stimulus in a set. Keywords Strength  Weight training  Hypertrophy  Lateral raise Introduction The momentum of a moving object is a physical quantity intimately linked to the object’s kinetic energy and the force that needs to be applied over time to bring the object to rest. In performance-oriented sports, the ability to develop momentum by means of rapid force production is a highly desirable capability. For e.g. the momentum of the shot put at the time it is released by the athlete had in part been supplied to it by a direct action of the athlete’s muscles and in part transferred to it from the momentum of the athlete’s spinning body (Costa et al. 2000). In sprinting, the momentum of the sprinter is developed by the reactive force from the ground, equal in magnitude to the force exerted by the sprinter against the ground (Jaric and Markovic 2009). Considering the role that momentum plays in these sports it is no surprise that its importance is also reflected in the resistance training practices of the athletes. This involves the choice of loads which are suf- ficiently heavy to demand high force output but not so heavy to compromise the athlete’s ability to accelerate it rapidly. Momentum is an important factor in resistance training itself too, and can greatly affect the amount of load that can be lifted successfully and the effort required to do so. In a compound exercise such as the squat which involves a coordinated action of several functionally separate muscle groups, the momentum generated following the full squat position can be used to overcome the subsequent biome- chanical weakness at the mid-point of the concentric part of the lift. A similar technique can be used in the bench press Communicated by Jean-Rene ´ Lacour. O. Arandjelovic ´(&) Swansea University, Swansea SA2 8PP, UK e-mail: oa214@cam.ac.uk; ognjen.arandjelovic@gmail.com 123 Eur J Appl Physiol DOI 10.1007/s00421-012-2420-y