Back stabilization during knee strengthening exercise

Twenty normal women were tested for maximal isometric contraction of the right knee extensor muscles. The knee was positioned in 60 degrees of extension and the hip at 120 degrees of extension, with and without a backrest. The purpose of the study was to determine whether the use of a backrest resulted in greater force than when not using a backrest when the angle of back inclination was held constant and the support was varied. The results indicated that the addition of a backrest, when the body assumes an optimal position, enables the knee extensors to generate greater force then when no backrest is used. A backrest adds to the comfort and support of the subject performing resistive knee exercise and should be incorporated into the design of knee exercise units.