Absolute strength is the maximum amount of force a muscle can exert under involuntary stimulus. Though it is the greatest strength potential in an individual’s muscles, the body has receptors that keep it from reaching this level on a regular basis. This is because constantly using that much strength can harm the body. The body bypasses those receptors in emergency situations so that it can function at its optimum level. In order to reach maximum strength, bodybuilders will often train with the goal of attaining the highest possible percentage of absolute strength.
It is possible to measure the exact level of absolute strength in a laboratory setting. By attaching electrodes to the muscle, the resulting involuntary twitches will display the maximum possible amount of effort possible without conscious participation from the subject. In order to obtain an accurate reading, the current is raised as high as the subject can tolerate.
In most situations, the body will hold back from using energy up to its absolute strength threshold. While exercise — particularly strength training — may bring a person closer to that level, there are other processes in the body beyond conscious control which prevent the full use of muscular resources. Usually the body will only use absolute strength in extreme situations, such as matters of life and death where extra stores of energy are needed. This is why someone who would not normally be seen as particularly strong could suddenly perform amazing feats of strength in the midst of an emergency.
Maximum strength is the top level that a person can reach voluntarily. This threshold can be increased with training and come very close to the level of absolute strength, but it is not likely a person would be able to reach 100%. This is partly because the body is only meant to handle so much strain over the long term. It is also because the body is also supposed to always have a reserve of strength it can use in times of peril. The level of maximum strength can be measured with simple exercises, such as squats and repetitions with weights.
Other kinds of strength include concentric, eccentric, and isometric. The first is the amount of energy a muscle can exert when it is contracted. Eccentric energy is how much power the muscle has when it is stretched out. With many kinds of exercises, the muscles will switch back and forth between these kinds of energies with the performance of repetitions and other similar kinds of moves. Isometric is the level of strength a person has to hold a weight or position.