How to correctly combine endurance and strength training

Those who want to get or stay physically fit often pursue two central goals: more strength and better endurance. Therefore, it makes sense to combine both. Be it through classic running sessions alongside strength training, interval training, spinning, or intensive functional training. Especially in Crossfit, the combination of strength and endurance has long since become an integral part of training. But the question keeps arising as to whether these two forms of training might possibly get in each other's way. The term interference effect describes exactly this phenomenon: that too much or poorly planned endurance training could hinder muscle growth and strength gains. But how big is this effect really? And does it affect everyone or just very ambitious athletes? In this article, we look at when it makes sense to separate strength and endurance training, what effects the combination can actually have on your progress, and how you can plan both so that you become stronger, fitter, and more capable without holding yourself back.

In a nutshell

For anyone who can't focus longer than a goldfish on caffeine – here is the juice without the veggies:

• Yes, there is an interference effect – especially with high intensity in both types of training.
• For many recreational athletes, the effect is negligible.
• Those who want maximum strength or muscle mass should separate the sessions – at least six hours apart or on different days.
• Those who just want to be generally fit can combine both – preferably: strength first, then cardio.

And off we go.

What is the interference effect

The interference effect describes the phenomenon that endurance and strength training can negatively influence each other when combined unfavorably. Strength training triggers completely different signals in the body than endurance training. While strength stimuli primarily promote muscle growth, endurance training activates a certain metabolic pathway, which can slow down muscle growth. This means: if you overdo it, too much endurance training can interfere with muscle-building processes.

When should you separate strength and endurance training

If your main goal is to build as much muscle mass as possible or significantly increase your maximum strength, you should separate strength and endurance training. For example, those working toward maximum hypertrophy or new personal records in deadlifts or bench presses benefit from not performing endurance sessions directly before or after strength training. It is ideal to have at least six hours between the two types of training. Or better yet, when they take place on different days. Very intensive and frequent endurance training, such as interval runs, HIIT sessions, or long bike rides, can have a negative impact on your recovery and performance during strength training. In such cases, you should consciously plan when you train what and ensure that your body has enough time to recover. And finally, it is worth taking a closer look at the training structure if you feel you are not making progress. Stagnating strength values, chronic fatigue, or persistent muscle soreness can be signs that your body is overwhelmed by the combination of strength and endurance training. In such cases, it can be helpful to uncouple the training types or reduce the volume to give the body more room for adaptation.

When is a combination not a problem or even useful

For most people who are not working toward a competition or maximum strength performance, it is no problem at all to combine strength and endurance training. Especially for recreational athletes who want to improve their general fitness, this can even be the best solution. The mix of both training forms ensures more energy in everyday life, a better body awareness, and all-around healthy physical performance. Especially in functional training approaches like Crossfit, this combination is implemented very skillfully: training often begins with a targeted strength part and ends with a short, intensive endurance block or a combination of both. This covers both areas without the training stimuli interfering too much with each other. A workout that combines strength and endurance saves time, increases training density, and brings progress on multiple levels. In such cases, however, it makes sense to plan the sequence well: those who perform the strength exercises first can fully concentrate on technique and load before the cardiovascular system is challenged in the second part of the training. Even those who regularly fit both forms of training into their week do not need to worry about interference effects as long as the endurance sessions remain in a moderate range.

How big are the differences really

Scientific studies show:

• The difference in muscle growth when combined simultaneously is about 10–15% less gain compared to pure strength training
• In terms of strength development, it can be 5–20% less progress – depending on training intensity and design.

Meaning:

• For the average athlete, these are manageable differences.
• For ambitious strength athletes or bodybuilders, however, this effect can be decisive.

What about Crossfit

Crossfit is a prime example of how strength and endurance training are consciously combined, often within the same training session. It is not uncommon for heavy exercises like deadlifts, thrusters, or cleans to be combined directly with burpees, jump rope, or running. This mix is no coincidence, but part of the concept of General Physical Preparedness (GPP). That is, the idea of being ready for as many physical challenges as possible. Crossfit does not want maximum specialization, but rather to promote broad, functional fitness: strength, endurance, mobility, coordination, and mental resilience. But how does this reconcile with the interference effect? Crossfit consciously accepts this effect, because the goal is not maximum hypertrophy or records in powerlifting, but a fit, capable body that performs well or even above average in many areas.

Conclusion

Strength and endurance training do not necessarily have to be separated. On the contrary: for many people, the combination of both actually works excellently. Especially in functional training, the two forms of training complement each other meaningfully and lead to a balanced, everyday fitness. Nevertheless, in certain situations, it can be useful to specifically separate strength and endurance phases. If you want to specifically build muscle mass or significantly increase your maximum strength, then a well-thought-out training plan with a clear structure and sufficient recovery pays off. Ultimately, it is not just the form of training that decides, but how cleverly you structure your training, how well you design your recovery phases, and whether your sessions fit your personal goals.