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A summary of Chapter 3 from "Body by Science" - Doug McGuff and John Little.
Dr. Dough McGuff introduces an interesting parallel in his book “Body by Science”. He observes an analogy between medicine and training. Both represent a stimulus for the body and for both there is an optimal dosage and a resulting necessary concentration for optimal effect. There is also an optimal frequency of administration for both of them. Everyone knows the scribble note from the doctor or the instruction of the pharmacists: "3x a tablet each day", of course 3x being the frequency and "a film-coated tablet" being the dosage.
In our case, the intensity of the training would correspond to the concentration in medicine. The dosage would be the number of exercises in a workout. And the frequency of administration is the number of workouts per week.
In addition, there is a so-called therapeutic window of dosage and frequency in both physical training and medicine. Exceeding this therapeutic window does not increase the benefit, but the toxicity...as with the medicine.
In medicine, the effectiveness of a drug is measured based on the concentration required for a physical reaction. In strength training, the efficiency can be determined by how many muscle fibers are activated in order to overcome the resistance during a certain exercise. One speaks of low intensity when our brain has to activate only a few muscle fibers and of high intensity when activating many fibers.
So the brain controls the muscle fibers to overcome resistance. The brain does this in a certain order of muscle fiber recruitment using the so-called motor neurons of the central nervous system. The order of recruitment refers to the two main types of muscle fibers that are provided in our muscle anatomy.
The types of muscle fibers are roughly divided into 1. “Slow Twitch” and 2. “Fast Twitch” muscle fibers. (Whereby "Slow" and "Fast" do not indicate the speed of contraction, but the speed of fatigue). In general it can be said that the "Slow Twitch" muscle fibers fatigue slowly but at the same time cannot produce much strength. Therefore, these are mainly addressed in endurance sports, for example during a hike. The "Fast Twitch" muscle fibers, on the other hand, generate great strength, but also tire quickly. These "Fast Twitch" muscle fibers have a large mass potential and occur genetically, especially in people who are naturally very muscular.
It is worth knowing that the "Fast Twitch" muscle fibers in the literature are additionally divided into three different types:
Our brain hates having to spend energy on something. This is a valuable survival mechanism from evolution. The brain decides to control the "Slow Twitch" muscle fibers first, because they need little energy. As mentioned above, the "Fast Twitch" muscle fibers differ into three subcategories: a) relatively fatigue-resistant, b) medium fatigue resistance, c) fast-fatiguing. The latter, the fast-fatiguing "Fast Twitch" muscle fibers, require the most energy. In response to resistance to be overcome, the brain controls all muscle fibers in the order of their respective energy requirements. If the resistance is now high enough, the brain will activate all fiber types in this order.
It is important for the choice of training intensity that our brain does not target the muscle fibers accidentally. The speed of contraction is also of no interest, only the resistance that has to be overcome. Accordingly, the minimum amount of muscle fibers that is required to overcome resistance is addressed. 
It is important to repeat that the terms "Fast Twitch" and "Slow Twitch" do not refer to the rate of contraction, but to the speed of fatigue. They have a high number of phosphagens and enzymes of the anaerobic metabolism, which converts glucose into lactate and energy (ATP) via the so-called lactic acid fermentation. Lactate is a by-product of this process and is responsible for the well-known muscle burning during training. At this point, reference should also be made to the article "The Science of Fat Loss", which deals with this topic in detail.
In addition, the amount of microtrauma at fiber level increases with the intensity of the training for the muscle, which leads to a positive adjustment. 
The rapidity of fatigue goes hand in hand with the regeneration speed of these "Fast Twitch" muscle fibers. The faster they tire, the slower they recover.
So it depends on the intensity of the strength training whether all fiber types are actually used in order to provoke the greatest possible and advantageous adaptation reaction. In traditional strength training with weights or weight-based devices, training at the effective performance limit of the body harbors high potential for injury and suffers from inefficiencies. Thanks to our adaptive resistance technology, we can control the target muscle optimally and safely from the start and train muscle groups holistically over a period of 60 seconds, which means that all types of fibers can be reached.
The "Fast Twitch / Fast Fatiguing" fibers that are addressed by our training would only have been activated in our "hunter and gatherer" past in an absolute emergency. These situations were rare and irregular. However, the depth of such stimuli harbors great health benefits. Because of their slow recovery time, these fibers once completely fatigued take four to ten days to fully recover. If you were to train the same muscle group again after three days, it would be impossible to achieve the same peak performance as before. But if you allow the body to relax for 7-10 days, all muscle fibers are ready for action again and even stronger than at the beginning of the previous training.
An additional advantage of our training technology is that we save every second of every training session in the cloud and we evaluate this together with you. This eliminates the regeneration guessing game. If progress slows down, we extend the regeneration phases before we modify the training. This goes against the usual practice of increasing the training frequency or even intensifying the training as soon as there are no successes. This is a mistake that is common in traditional fitness clubs. With the analysis of the data and clear, science-based action, there is no doubt about it. 
Training at Aurum Fitness enables the activation of all types of muscle fibers. This enables us to get the maximum benefit from strength training. At the same time, our training philosophy also takes into account the client's individual ability to recover in order to guarantee optimal results.
 H.S. Milner-Brown, R.B. Stein, and R. Yemm, «The Orderly Recruitment of Human Motor Units During Voluntary Isometric Contractions”, Journal of Physiology 230, no. 2 (April 1973): 359-70; H.S. Milner Brown, R.B. Stein, and R.Yemm, “Changes in Firing Rates of Human Motor Units During Linearly Changing Voluntary Contractions”, Journal of Physiology 230, no. 2 (April 1973): 371-90. See also Journal of Neurophysiology 55, no. 5 (May 1986): 1017-29, and Journal of Neurophysiology 57, no. 1 (January 1987): 311-24.
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 P.M. Clarkson and I. Tremblay, "Exercise Induced Muscle Damage, Repair and Adaption in Humans", Journal of Applied Physiology 65, no. 1 (1998): 1-6; L. L. Smith, "Acute Inflammation: The Underlying Mechanism in Delayed Onset Muscle Sorenss?" Medicine and Science in Sports and Exercise 23, no. 5 (1991): 542-51.
 D.R. Taafe, C. Duret, S. Wheeler, and R.Marcus, "Once Weekly Resistance Exercise Improves Muscle Strength and Neuromuscular Performance in Older Adults", Journal of American Geriatric Society 47, no. 10 (October 1999): 1208-14; J.R. McLester, P. Bishop, and M.E. Guilliams, "Comparison of 1 Day and 3 Day per Week of Equal-Volume Resistance Training in Experienced Subjects", Journal of Strength and Conditioning Research 14 (2000): 273-81. (In this study subjects who had an average training history of 5.7 years were put on a whole-body training program, consisting of nine exercises performed either one or three times per week. After the study, a post-test conducted on eight of the nine strength measures indicated that there was no statistical difference between the two groups, which led the researchers to conclude that training once per week delivered the same results as training three times per week.)