A muscle strength measuring apparatus has a force receiver connected to a force sensor. An upright bracing surface is rigidly positioned with respect to the force receiver to provide a testing space between the surface and the force receiver. The receiver is adjustable such that a person standing in the testing space can brace against the surface and exert a force against the force receiver with a first muscle on each side of the person's body, and can then adjust the position of the force receiver and exert a force against the force receiver with a second muscle on each side. Thus comparative strengths of muscles on opposite sides of the person's body can be accurately determined by measuring the isometric force exerted by corresponding muscles on each side.