Why you get stronger through training

Along with looking good naked, getting stronger is a primary goal for many people starting out with weight training. Whether it is about lifting heavier weights, strengthening the body for everyday activities, or improving physical performance in sports – strength is a fundamental factor. But what exactly happens in the body when you get stronger? How are muscle mass and strength related? And what role do the different muscle fiber types play in this process?

The mechanisms of why weight training makes you stronger

Weight training triggers a series of adaptations in the body that lead to an increase in strength. These adaptations affect both the nervous system and the muscles themselves. Among the most important mechanisms are:

Neural adaptations
The initial improvements in strength observed during training are usually not due to muscle growth (hypertrophy), but rather to neural adaptations. This means the nervous system becomes more efficient at activating muscles. The following aspects are responsible for this:

Improved muscle fiber recruitment: The nervous system learns to activate more muscle fibers to execute a movement, leading to increased force.

Synchronization of muscle activity: Different muscle groups work together better. The interaction between agonists (muscles that perform the movement) and antagonists (muscles that control the movement) becomes more efficient.

Increased motor unit firing rate: The nerves that control the muscles send their signals faster, allowing for a more powerful contraction.

These neural adaptations are particularly pronounced in the first weeks and months of training and ensure that one gets stronger relatively quickly before muscle growth takes center stage.

Muscle hypertrophy (muscle growth)
After some time, muscle hypertrophy sets in, meaning the muscle fibers become thicker. This occurs through an increase in the number of contractile proteins within the muscle fibers that are responsible for force generation.

Increased protein synthesis: Microscopic tears occur in the muscles during training. The body repairs these tears by incorporating more protein into the muscles, leading to thickening and thus to greater contractile force.

Satellite cell activation: These stem cells located around the muscle fibers are activated by training and contribute to muscle repair and growth.

Hypertrophy is a longer-term adaptation mechanism that develops over time, especially with strength training involving moderate repetition ranges and heavy weights.

Connective tissue adaptations
Tendons, ligaments, and connective tissue also adapt to training. These structures become more resilient, which contributes to joint stability and improves the transmission of force from the muscles to the bones.

Metabolic and hormonal adaptations: Strength training improves energy storage in the muscles (glycogen) and makes the body respond more efficiently to anabolic hormones like testosterone and growth hormone. These hormones promote protein synthesis and thus contribute to muscle repair and growth.

Does strength correlate with muscle mass?

There is a correlation between muscle mass and strength, but it is not directly proportional. The reasons for this are as follows:

Neural efficiency: In the early stages of training, strength is gained primarily through neural adaptations without significant increases in muscle mass. This means it is possible to get significantly stronger without building much muscle mass. A well-trained nervous system can activate more muscle fibers simultaneously and transfer force optimally.

Muscle cross-section and strength: As muscle mass increases, strength normally increases too, as larger muscles contain more contractile proteins. A larger muscle has a greater capacity to develop force because it possesses more potentially activatable muscle fibers. However, there are many cases where a person with smaller muscles is stronger because they have better neural efficiency and technique.

Leverage and technique: It is not just muscle mass that determines strength, but also biomechanical leverage and technique. A person with better leverage (e.g., due to longer lever arms) can lift heavier weights even if they have less muscle mass.

What muscle fibers are there and what are their functions?

Muscles consist of different types of muscle fibers, each specialized for different tasks. There are two main types of muscle fibers:

Type I fibers (slow-twitch fibers)
These fibers are designed for endurance performance. They contract more slowly but are more resistant to fatigue. They have a high capacity for aerobic metabolism (oxygen utilization) and are used primarily in activities such as long-distance running or cycling.

Hypertrophy: Type I fibers can grow, but their capacity for hypertrophy is limited compared to Type II fibers. They respond more to longer, less intense loads.

Type II fibers (fast-twitch fibers)
These fibers are specialized for fast and powerful movements. They contract quickly but also fatigue faster. There are two subtypes:

Type IIa: These fibers are a mixture of endurance and strength fibers. They are suitable for both power-based and light endurance activities.

Type IIb: These fibers are specialized for maximum strength and speed and are activated during very intense, short-duration efforts like sprints or one-rep max attempts.

Hypertrophy: Type II fibers have a much greater capacity for hypertrophy than Type I fibers. They grow particularly well in response to heavy strength training and explosive movements.

How does training affect the different muscle fibers?

Endurance training primarily promotes the development and endurance of Type I fibers and also makes Type IIa fibers more resistant to fatigue. Strength training mainly activates Type II fibers, particularly Type IIb, and leads to their hypertrophy. Fast, powerful movements are key to unlocking the full potential of these fibers.

Conclusion

Strength training leads to a multitude of adaptations in the body – from neural improvements to muscle growth and structural changes in muscle fibers. Although muscle mass and strength correlate, neural efficiency, technique, and muscle fiber types play an equally large role. The fast-twitch Type II fibers are particularly important for strength gains, as they respond best to strength training and have the greatest capacity for hypertrophy.

To unlock the full potential for strength and muscle growth, it is crucial to tailor training to your personal goals and pay attention to both neural efficiency and hypertrophy.