Cardio and Strength Training — Do They Work Against Each Other?

A common fear among lifters is that cardio will "eat their gains." On the other side, endurance athletes worry that lifting will make them heavy and slow. Both groups are operating on a half-truth. The relationship between cardio and strength training is more nuanced — and more manageable — than either camp typically acknowledges.

The interference effect: what it actually is

The interference effect is a real phenomenon. Concurrent training — doing both cardiovascular exercise and resistance training — can blunt adaptations to both modalities compared to doing each in isolation. In practice, this means:

• Long-distance endurance training signals the body to become more efficient aerobically, which can conflict with the signals for muscle growth.
• Excessive cardio volume increases recovery demands, leaving less capacity for strength adaptations.
• Doing cardio immediately before lifting impairs strength performance in that session.

However, the effect is much smaller than most people assume, particularly at moderate cardio volumes. The research shows interference becomes meaningful mainly when cardio volume is high (5+ hours per week) and is done in the same session as lifting, especially before rather than after.

What the research actually supports

For the average gym-goer doing 3–5 lifting sessions and 2–3 cardio sessions per week:

• Cardio does not meaningfully reduce muscle growth. Multiple meta-analyses have found that moderate concurrent training produces similar hypertrophy outcomes to lifting alone.
• Cardio does not reduce strength gains significantly. The effect on maximal strength is small and practically irrelevant for most people.
• Cardio improves work capacity. Better cardiovascular fitness means you recover faster between sets, can handle more training volume, and feel better during high-rep work.

The interference effect is largely a concern for competitive athletes optimising for one specific goal. For most people, it's a non-issue if you programme sensibly.

How to structure cardio alongside lifting

Separate cardio and lifting sessions

The most effective approach is to keep cardio and strength sessions as far apart as possible — ideally on separate days, or at minimum with several hours between them. Doing legs in the morning and a 5km run in the evening is far better than combining them.

If you must do both in one session

Do lifting first, cardio after. The reverse order — cardio before lifting — acutely impairs strength performance. Your central nervous system is fatigued, your muscles are partially depleted, and your performance on the main lifts suffers. Doing cardio after lifting means your strength work isn't compromised, and the cardio volume is the only thing that takes a hit — which is usually an acceptable trade-off.

Match cardio type to your goals

Low-intensity steady-state (LISS) — walking, cycling at a comfortable pace, easy rowing — has the least interference with strength training. It's aerobically beneficial without placing huge demands on your muscles or nervous system.

High-intensity interval training (HIIT) is effective for cardiovascular fitness but significantly increases recovery demands. Treat HIIT sessions like a hard lifting session and schedule them accordingly. Don't do HIIT the day before a heavy squat session.

Running places significant eccentric load on the legs, particularly longer runs. If you're also doing heavy leg work, manage the total volume carefully and ensure adequate recovery between leg-intensive sessions.

Watch total weekly volume

The interference effect scales with cardio volume. Two or three cardio sessions of 20–40 minutes per week is unlikely to cause any meaningful interference. Ten hours of cardio per week alongside heavy lifting is a different story. Be honest about your total training load and recovery capacity.

Cardio has real benefits for lifters

Beyond health and body composition, cardiovascular fitness makes you a better lifter:

• Faster between-set recovery. You'll get your breath back quicker, meaning you can take shorter rest periods or start the next set feeling more ready.
• Higher training volume ceiling. Fitter lifters can handle more total sets before fatigue accumulates.
• Better nutrient partitioning. Aerobic fitness improves insulin sensitivity, which means nutrients are more likely to be shuttled toward muscle rather than fat.

The bottom line

Unless you're training for a specific performance goal that demands maximum adaptation in one direction, cardio and strength training are not enemies. They're complementary — as long as you programme them intelligently.

Keep them separated where possible, do lifting first when they share a day, manage total volume, and prioritise recovery. Track your sessions so you can see if cardio is actually affecting your lifting performance, and adjust if it is.

The best programme is always the one that fits your life and that you can sustain. For most people, that includes both.