March 27, 2026, 4:00 am | Read time: 5 minutes
Afraid of muscles? There’s a training method that can specifically increase strength without visibly building muscle mass.
Why many runners avoid strength training
Many runners or other endurance athletes shy away from strength training, fearing they will visibly gain muscle mass. After all, mass also requires energy. Of course, big muscles don’t make running impossible–but they can make it more difficult. On the other hand, muscles are often the key to better times, more stability, and fewer injuries. The good news: There’s a way to get stronger without building visible muscle mass.
Building strength without getting bigger muscles–3 key factors
“It’s not possible without any hypertrophy, but the increase in muscle cross-section can be minimized by various means,” says Enrico Zessin, a specialist in internal medicine and sports medicine and team doctor for the German Athletics Association, to FITBOOK. To become stronger while keeping muscle growth to a minimum, three factors are crucial: high weights, few repetitions, and long breaks.
The crucial lever: Strength through the nervous system
“The fear of quickly building visible muscle mass through strength training is unfounded in most cases,” says Zessin. The body responds to strength training in two ways: neural activation improves–or the muscle cross-section grows.
What’s crucial is which of these predominates, and that depends on the training. Traditional muscle-building training focuses on high volumes, many repetitions, and training to exhaustion. But that’s not what runners need.
Those who want to get stronger without visibly building muscle mass need to think about training differently. The focus is not on the muscle itself–but on the nervous system. It learns to activate more muscle fibers simultaneously. The result: more strength without necessarily more volume.
“Very high loads with few repetitions primarily stimulate the nervous system,” explains Zessin. With few repetitions, the body learns to activate more muscle fibers simultaneously–an effect that mainly improves strength without necessarily leading to more muscle mass.
Why some build muscle faster than others
Our muscles consist of different fiber types, each with different properties. “There are differences in the supply and metabolism of the respective fiber types, and the composition and ratio of Type I and Type II fibers is different for each person and genetically determined,” explains Zessin.
- Endurance-oriented muscle fibers work efficiently and fatigue slowly but hardly grow (Type I fibers)
- Fast-twitch fibers, on the other hand, can develop more strength–and have a significantly higher growth potential (Type IIx fibers)
- (Type IIa fibers are the hybrid form of Type I and Type IIx fibers)
According to Zessin, only the ratio of Type IIa to Type IIx fibers “can be partially changed through specific training.”
This also means that some people are better suited for endurance sports, while others are more suited for intensive strength sports. “And it explains why some people experience rapid muscle growth with little strength training, while others have to train for a long time to see a visible effect,” says the sports physician.
Specific training formula for minimal muscle growth
To minimize muscle growth, strength training should meet certain criteria. “Sets with moderate to higher weights and relatively low repetitions can be useful to improve strength without triggering a strong growth stimulus,” explains Zessin. He then recommends this training formula:
- Training at 85 to 100 percent of the One-Repetition Maximum, or 1RM (meaning very high intensity)
- 1 to 3 repetitions,
- 3 to 5 sets (avoiding muscle failure),
- 3 to 5 minutes of rest.
The long breaks between sets reduce the accumulation of metabolic products and thus muscular stress.
Also interesting: Slim, toned legs–10 min. workout
A single repetition in the weight room? Why that’s not enough
“A single repetition is not enough in practice to achieve a sustainable training effect,” says Zessin. So, to maintain muscle and become stronger. The combination of intensity, proper execution, and a certain regularity is crucial.
Applied to the example of a runner, these are the stimuli that make them more efficient–and not bulkier.
How runners can set strength stimuli without getting (visible) muscles
Zessin: “For runners, about two-thirds of the training should be in the endurance area to build the foundation for peak performance. Only with well-developed basic endurance are intensive performances stably possible.”
On top of that, he recommends peak loads for running-specific maximum strength. These specifically train explosive strength and neural activation–without a focus on traditional muscle building. Running-specific stimuli are set with:
- Short sprints
- Stair or hill runs
- Tempo change games (Fartlek)
- Jump exercises where you push off explosively
- Strength exercises with high weight as described above, e.g., with the barbell
For me as a runner, it’s not about how much muscle there is
“For runners, it’s not about how much muscle there is–but how efficiently it works. No serious expert would likely recommend training specifically to prevent muscle growth. A certain amount of muscle building and especially maintenance is always beneficial for health, with keywords like sarcopenia and injury prevention. And if an endurance athlete only trained in the endurance area, performance development would eventually stagnate. Those who want to improve as endurance athletes inevitably need regular intense stimulation and stimuli through exercises so that the muscles and metabolism can adapt accordingly.”
What Are the Benefits of Bigger Muscles–and How Do I Get Them?
Increase Muscle Growth With Progressive Overload
Nutrition against excessive muscle hypertrophy
With the right nutrition, you can also influence (unnecessary) muscle hypertrophy to your advantage. Significant muscle growth usually only occurs with a corresponding calorie surplus. Unnecessary protein intake should also be avoided, as it leads to muscle hypertrophy more quickly.
In general, nutrition should always be balanced and meet individual needs. Those who eat a balanced diet and do not specifically aim for muscle building need not “fear” visible muscles.
Conclusion
Strength training is not a contradiction for endurance athletes–but a crucial performance factor. What matters is how the training stimulus is set. Those who train with high intensity, few repetitions, and sufficient breaks can become stronger without visibly building muscle mass.