A Soloflex machine was analyzed mathematically. Dimensions of the components of the machine were measured, and calculations were made to determine a resistance curve. The machine consists of a mainframe bent into an L-shape, having a vertical post height of 6 ft. A loading post with 27 drilled holes is attached along the back of the vertical post. The loading piece receives a bench pin and the barbell arm pin. To perform an exercise, the barbell arm is attached with the barbell arm pin to the loading piece. Weight straps of equal rating are placed on both sides of the load and barbell arm pins. Pushing upward on the barbell arm will stretch the weight straps which provides resistance to the motion of the barbell arm. The weight straps behave like springs. The straps were stretched with a Tinius-Olsen machine to determine the force vs deflection behavior for a standard set of weight straps, including one pair each of 2.5 lb, 5 lb, 10 lb, 25 lb, 50 lb and 100 lb weight straps. The objective of this study was to make measurements of force versus deflection for each matched pair of weight straps, and then to calculate the force required at the barbell arm to perform an exercise for a particular "weight." Although several different exercises can be performed, the focus here is on a simple bench press, for which the resistance curve was determined.

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