Exercise devices are used to exercise certain muscle groups or muscles and joints, whereby a muscle and joint are subjected to stress. For exercising different muscles and joints, the manufacturers design various pieces of equipment whose common feature is that the movement and strength of muscles and joints are transmitted by means of transmission mechanisms to a counter-action device, which counteracts this force. Hence, ready adjustment of the load of a counter-action device is essential, since the load determines the strength of this resistance force and the load must be readjusted quite often because of a variety of persons to practice and purposes of exercise.
In the present exercise devices, the most commonly used counter-action device comprises a stack of weight slabs. A stack of weight slabs generally includes approximately 10 to 30 weight slabs of equal size and weight. A desired number of weight slabs are mounted e.g. by means of a cotter on a transmission mechanism, whereby the load can be varied according to the number of weight slabs. Furthermore, a stack of weight slabs is generally guided by guiding rods or the like. This type of counter-action devices are safe, noiseless and their load adjustment can be readily and quickly effected.
A problem usually encountered in the use of a stack of weight slabs is the inadequate number of weights when using the same device for both normal keep fit programs and heavy exercise action. Thus, the weights are not always sufficient for even an amateur, let alone a strong athlete. In order to increase the load, it is necessary to suspend from a stack more weights, e.g. weight lifting discs, which is dangerous and inconvenient. If there is a sufficient number of weight slabs, the stack will be so high that, together with the displacement range required by said stack, the device will become too high, circa 2 to 3 meters, whereby working of a large number of slabs for a stack increases costs even further. If heavier, in other words longer and wider slabs are made, a stack of slabs won't grow unduly high. However, the increase or gap between weights will then be too much. When working on rather small practice weights, an increase of 10 to 15 kg at a time may be far too much. In addition, the options of choosing the total load will be too few. Another possibility is to adjust the gear ratio of transmission in a manner that even a small weight feels sufficiently heavy, thus eliminating the need for a large and high stack. In this case, however, a heavy gear ratio requires a long path of travel for the load and, secondly, the increase will be too much as a minor increase of weight means in fact a major increase because of the gear ratio. At the present time, when using a so-called normal stack of weights, it is necessary to compromise either with total load, proper increases or number of options unless the result is to be an exercise device 2 to 3 meters high, with over a meter high pile of costly manufactured weight slabs stacked therein.