Muscle hypertrophy is defined as the increase in the size of the cross-striped muscles. An optimal training stimulus can trigger muscular adjustments. The adjustment is basically made by an increase in muscle cell volume (thickness growth, length growth) and metabolically contractile reprogramming (Goldspink 1985).
All muscular adjustments are non-movement-specific and, therefore, transferable to other movements. Provided, however, that the adapted muscle fibres are also used in movement or sport. In muscle hypertrophy training, an attempt should be made to train the muscles as diversely as possible. This ensures that the muscles meet the requirements in sports or everyday life.
So what types of muscular hypertrophy are possible?
Radial adjustment (thickness growth)
+ muscular hypertrophy (more
parallel-switched sarcomeres) – muscular
atrophy (less parallel-switched sarcomeres) Longitudinal adjustment (length growth)
+ muscle hypertrophy (more sarcomeres in series)
– muscular atrophy/shortening (fewer sarcomeres in series)
A muscle can thus become thicker as well as longer. The respective adjustment is made via the number of sarcomeres. With a thickness growth, sarcomeres are thus multiplied in parallel. When adjusting the length, sarcomeres are increased serially.
Atrophy (decrease in thickness or length)
muscle mass loss as a result of inactivity, immobilization.
1. Radial atrophy
the decrease in physiological muscle cross-section resulted from a decrease in the cross-section of individual muscle fibres or loss of muscle fibres.
2. Length growth
the decrease in the length of each muscle fibre. The muscles can remove sarcomeres in series at the ends of the myofibril.
What is metabolic reprobation?
A change in muscle fibre distribution (type I, type IIa and type IIx) is possible to a limited extent. These adjustments are therefore associated with adjustments in mitochondrial content, vascularization, etc. The oxidative capacity is thus increased in the muscle. According to the current knowledge, converting type II fibres into type I fibres is not possible under normal circumstances. Through endurance training, you no longer get type I fibres.
Exclusive training also does not make the muscle fibres “faster”. Training of any kind thus leads to a change in muscle fibres from type IIx to type IIa. Inactivity (voluntary or forced) leads to a muscle fibre switch of type IIa to type IIx. So the muscle fibres get faster.
Is hyperplasia possible?
Hyperplasia is the increase in muscle cross-section by increasing the number of muscle fibres. According to current knowledge, there is no scientific evidence in humans, so it is assumed that an increase in the number of muscle fibres through training is not possible.