Resistance Training can be accessed through different modalities. Holding limbs in a stationary or static position does provide (some) strengthening benefits. Weight-lifting or body weight training are default methods that many people envision when considering resistance training. There are also training modalities that utilize resistance bands, stability balls or other appurati for (the) resistance. Resistance training can also be used for rehabilitative purposes. The point to be derived is that there are varying ways to obtain the benefits of toning and strengthening muscle.
The purpose and main result of resistance training is to stimulate muscle tissue and forestall the atrophy process. Stimulating muscle tissues is partial to the growth of size and or strength. This may be of importance for athletic endeavors as more strength translates to increased force generation on the field of play. Aesthetics may also play a factor here in that one may want to ‘improve themselves for health or appearance reasons. Muscle loss (atrophy), sarcopenia, is a major factor as one ages. In particular, the very mechanisms necessary for stimulating muscles are very contributory to forgoing the effects of (age related) muscle loss.
Isometric training involves holding limbs in stationary positions under static muscular load. This type of training can be part of a movement sequence (i.e. pausing (slightly) at the top of a kettlebell swing). This type of movement can be done for extended periods of time. Various martial arts training and some aspects of yoga utilize this approach. There is also application for rehabilitation. The specific quality of isometric training is that is strengthens the muscle at one point of movement. One may want to strengthen the muscles at the point where a joint is weakest. One can use this modality for strengthening the joint(s) at the full extension of a punch.
Isotonic training involves overcoming resistance due to muscular contraction, relaxation and stabilization. Something is moving / being moved; be it the body or some external object. This type of training can be approached in (many) different ways. It is an established manner for improving the overall tone and function of muscle. Most programs for bodily improvement are primarily focused on muscle tone. Body weight movements, weights, or other appurati are utilized for improvement the appearance and function of muscle. This type of training has the added benefit of increasing muscle tissue energy demand. This is a key ingredient for fat loss.
Isokinetic Training a clinical term that refers to strength training of a target muscle group muscle tissue graduated modes of resistance at a constant speed level. Machines and and other types of equipment are what facilitates this type of training. It is used, primarily, for rehabilitation purposes. Yet, some of these same machines can contribute to an overall strength and conditioning or body building regimen. Specifically, targeting a muscle or group of muscles can significantly enhance the overall output for certain movements in a chosen discipline. Whether adjunct to or main focus of a chosen regimen, isometric training is very effective.
There is one more type of resistance training that has not yet been mention. that of dynamic tension. Dynamic Tension is a self-resistance exercise method which pits muscle against muscle (synergistic versus antagonistic). The practitioner tenses the muscles (antagonist) of a given body part and then moves the body part (synergist) against the tension as if a heavy weight were being lifted. Dynamic Tension exercises are not merely isometrics, since they call for movement.
The takeaway is that there are three modes through which resistance training can be accessed. Actually, they are not necessarily stand alone modes, in the pure sense. Aspects of one can be (utilized as) a part of another. For example, isometric moves can slowly transition to other (isotonic) within the confines of an isometric regimen. Strongmen may want to use isometric or isokinetic modalities to improve the overall ability to hold longer or push a little hard. There is no hard and fast ‘winner take all’ aspect to resistance training. The key is to engage in it on a consistent basis.
Forces never rest . . . why should we????