This article is the result 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, fatty tissue and bones via the release of so-called myokines. As a result, skeletal muscle mass performs vital tasks, 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 article is on a comparison of different approaches in relation to the variable factors of resistance training, the so-called mechanical-biological descriptors. These are, for example, the load, number of repetitions, rest periods between sets, voluntary muscle fatigue and range of motion. The authors drew conclusions from the studies examined with regard to the variable factors for the performance of strength training. In their view, however, many of the studies were conducted with test groups that often did not take into account different age groups, genders and skill levels. The authors conclude that many of the variable factors have less influence on muscle growth than generally assumed. Some of the conclusions are briefly explained here:
Load (weight):
The 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 the development of muscle mass and strength is the metabolic load depending on the necessary substrates.
Rest intervals between sets:
The rest interval between each set 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 an increase in 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, the full ROM should be aimed for wherever possible.
