Cardio and strength training: can you progress in both?

Two disciplines long presented as incompatible

For a long time, the answer seemed obvious. If your goal was to build muscle mass or strength, you had to avoid cardio. Many feared it would “burn off” muscle, slow recovery or prevent the adaptations linked to strength training.

Conversely, endurance-sport enthusiasts sometimes believed that strength training risked harming cardiovascular performance by unnecessarily increasing body mass. These two disciplines were often presented as incompatible.

This idea is still widespread. It is not uncommon to hear that you must choose between running fast or lifting heavy, between building endurance or building muscle.

Yet research conducted over the past decades paints a much more nuanced picture. Yes, it is possible to progress simultaneously in strength training and cardio. However, this combination requires more thoughtful programming: the type of cardio, its intensity, its volume, its placement within the week and training level all directly influence the results obtained.

The real question, then, is not whether to combine cardio and strength training. It is understanding how to organise them so that they complement rather than hinder each other.

Why do cardio and strength training seem incompatible?

This idea stems largely from a phenomenon known as the interference effect. In the 1980s, several studies suggested that combining strength training with endurance training could slow gains in strength and power.

This observation seemed logical. The two types of training impose different physiological demands. Strength training mainly aims to increase the muscle's capacity to produce force and to build mass. Endurance training instead aims to improve oxygen use, cardiovascular adaptations and resistance to prolonged effort.

For several years, many interpreted these results as proof that you had to choose between the two. Modern research shows, however, that this conclusion was heavily oversimplified: interference depends strongly on how the two forms of training are organised.

What the scientific literature actually shows

Early studies sometimes observed a decrease in strength gains when very high volumes of running were combined with strength training sessions. Since then, numerous systematic reviews and meta-analyses have helped clarify this relationship.

Their conclusion is relatively clear. In the majority of trainees, a moderate volume of cardio does not prevent the development of muscle mass or strength, provided the programme is well constructed.

The interference effect appears mainly when several factors stack up: a very high volume of endurance work, very intense sessions performed frequently, insufficient recovery, and inadequate energy or protein intake. In these situations, recovery capacity becomes the main limiting factor.

Conversely, a few weekly cardio sessions, intelligently built into the programme, generally produce very few negative effects on hypertrophy. The cardiovascular benefits obtained often more than compensate for this small potential interference.

The interference effect is not inevitable: it mainly appears when volume, intensity and recovery stop being managed carefully.

Do all types of cardio produce the same effects?

The answer is no. The training mode used strongly influences the adaptations observed.

Running generates repeated impacts and significant muscular fatigue, particularly in the quadriceps, calves and tendons. When performed in large volumes, it interferes more with strength training performance.

Cycling, rowing and elliptical machines generally produce fewer mechanical impacts. They often allow cardiovascular capacity to be developed while limiting the fatigue linked to repeated impact.

Intensity also plays a role. Zone 2 work, done at moderate intensity, generates relatively low fatigue while effectively improving aerobic endurance. Conversely, very demanding HIIT sessions place greater demands on the nervous system and muscles, increasing recovery needs when combined with strength training.

Does the timing of cardio sessions matter?

How sessions are spread across the week also influences adaptations. Where possible, several researchers recommend separating cardio and strength sessions by several hours, or even scheduling them on different days.

This organisation reduces the immediate build-up of fatigue and allows each session to be approached with a higher level of performance.

If both forms of training must be done in the same session, the order generally depends on the primary goal. A trainee focused mainly on developing strength or muscle mass will benefit from starting with strength work. Conversely, an athlete preparing for an endurance competition will logically prioritise cardiovascular training.

For most trainees, this simple rule alone already limits a large part of the interference effects observed in some studies.

Can cardio even improve strength training performance?

When volume stays reasonable, cardio does more than just coexist with strength training. It can also offer several indirect benefits.

Better cardiovascular capacity aids recovery between sets. The heart becomes more efficient at transporting oxygen and nutrients to muscles, while certain by-products of effort are cleared more quickly. In practice, this often helps maintain a higher level of performance throughout the session.

Better overall fitness also makes it easier to string sessions together throughout the week.

Finally, cardio contributes to body weight control, improves cardiovascular health and reduces the risk of numerous chronic diseases. These benefits go well beyond the simple context of sporting performance. For this reason, most international recommendations encourage strength trainees to maintain regular cardiovascular activity.

The most common mistakes

The most widespread mistake is believing that any form of cardio automatically hurts muscle gain. Scientific data does not support this idea.

Another mistake is stacking multiple HIIT sessions on top of an already very demanding strength programme. The build-up of fatigue then becomes more problematic than the cardio itself.

Some people also do long running sessions immediately before their strength exercises. In this case, muscular fatigue often reduces the loads used and the technical quality of the movements.

Conversely, cutting out cardio entirely to “protect” muscle gains deprives the body of numerous health benefits, without offering any significant advantage for most trainees. The goal, therefore, is not to avoid cardio: it is to find a balance compatible with your priorities.

Practical recommendations

Keep two to three weekly sessions of moderate cardio, even during a muscle-building phase.

If strength training is your priority, do cardio after strength exercises or on different days.

Favour zone 2 work to build endurance while limiting fatigue.

Limit HIIT volume if your strength programme is already very demanding.

Make sure your diet and recovery properly compensate for the increase in energy expenditure.

Conclusion

The idea that you have to choose between cardio and strength training largely belongs to the past. Research now shows that these two forms of training can coexist effectively when their volume, intensity and organisation are well suited.

For most trainees, a few weekly cardio sessions prevent neither muscle gain nor strength gains. On the contrary, they improve overall fitness, support cardiovascular health and can even aid recovery between sessions.

The key, then, is not to eliminate cardio. It is to programme it intelligently so that it supports your goals rather than competing with them.