This paper emerged out of a collaboration between ETH Zurich and Kieser Training AG Zurich and compares current scientific findings on resistance training of skeletal muscles. In addition to locomotion, skeletal muscle mass has the function of regulating metabolic balance: muscles communicate with the liver, fat tissue and bones through the release of so-called myokines. In this way, skeletal muscle mass takes on tasks that are essential for survival, which makes the maintenance of muscle mass and thus resistance training essential as a strong stimulus for increasing muscle mass.
The main focus of this paper is a comparison of different approaches related to the variable factors of resistance training, the so-called mechanical-biological descriptors. These include load, number of repetitions, rest between sets, voluntary muscle exhaustion and range of motion. The authors drew conclusions from the studies considered in relation to the variable factors for the performance of strength training. However, in their view, many of the studies were conducted with experimental groups that often did not take into account different ages, genders and skill levels. The authors conclude that many of the variable factors have less influence on muscle gain than generally assumed. Some of the conclusions are briefly explained here:
Load or intensity for recreational athletes is overrated as both high and low loads can produce significant strength gains and hypertrophy as long as muscle exhaustion is achieved.
Number of repetitions:
A wide range of repetitions can be used to increase muscle mass and strength if the exercise is performed to muscle exhaustion. The main factor in developing muscle mass and strength is the metabolic load depending on the substrates required.
Rest between sets:
The rest interval between sets of resistance training to increase training volume does not appear to have any effect on muscle mass or strength. For recovery between training sessions, 24-48 hours per muscle group is recommended.
Voluntary muscle exhaustion:
Not a prerequisite for increasing functional and structural adaptations. In contrast, at lower loads, the number of repetitions to failure is essential for increasing muscle strength and mass.
Range of motion (ROM):
There are no absolute positive effects on hypertrophy when resistance training is performed over a full ROM compared to a partial ROM. Nevertheless, from a functional point of view, full ROM should be aimed for whenever possible.