Does Cardio Kill Gains? How to Do Cardio Without Losing Muscle
"Cardio kills gains" is one of the oldest lines in the gym. It's mostly a myth. The right amount of the right cardio won't stop you building muscle, and it's great for your heart. Here's what the research says and how to fit it in.
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Where the "cardio kills gains" idea comes from
It's called the interference effect. Endurance and strength training send your muscles different signals, so in theory doing lots of both could blunt muscle growth. In practice, it depends on how much cardio you do, what type and when.
What the research says
- Moderate cardio doesn't block muscle growth. A 2022 meta-analysis found concurrent training (cardio plus lifting) produced similar muscle growth and maximum strength to lifting alone. The one thing it blunted was explosive power, mainly when both were done in the same session.
- Dose matters. A 2012 meta-analysis found that the more often and the longer people did endurance training, the more it cut into muscle and strength gains.
- Running interferes more than cycling. In that same 2012 analysis, combining lifting with running reduced muscle and strength gains, while cycling didn't significantly. Running's pounding and the extra leg fatigue are likely reasons.
- Order matters for strength. A 2018 meta-analysis found that lifting before cardio in the same session led to better lower-body strength gains. Muscle growth wasn't affected by order.
Very well-trained lifters and anyone chasing peak power may notice more interference. For most guys training to build muscle and look good, sensible cardio is fine.
Why lifters should do cardio
- Heart health. The World Health Organization recommends adults get 150–300 minutes of moderate or 75–150 minutes of vigorous aerobic activity a week, plus muscle strengthening on at least 2 days.
- Better conditioning. You'll recover faster between sets and get less gassed on high-rep leg days.
- Less fat gain when bulking and easier fat loss when cutting.
- Recovery. Easy cardio on rest days gets blood flowing without adding much stress.
How much cardio for your goal?
| Goal | Cardio per week | Plus |
|---|---|---|
| Bulking | 2–3 × 20–30 min, mostly easy to moderate | Daily walking. Eat extra to cover it. |
| Recomp | 2–3 × 20–40 min | 7,000–10,000 steps a day |
| Cutting | 2–4 × 20–40 min | 8,000–10,000 steps a day. Diet does most of the work. |
| Heart health minimum | 150 min moderate or 75 min vigorous | Walking counts toward this. |
Moderate means you can talk but not sing. Vigorous means you can only say a few words at a time.
Best types of cardio for lifters
| Type | Interference with gains | Notes |
|---|---|---|
| Walking / incline walking | Very low | Easy to recover from. Great every day. |
| Cycling / bike | Low | Low impact. In untrained people it can even add a little leg muscle. |
| Rowing / elliptical | Low | Low impact, full body. |
| Swimming | Low | Easy on joints. |
| Running | Higher | Fine in moderation. Keep long runs away from leg day. |
| HIIT / sprints | Moderate | Time efficient but tiring. Keep to 1–2 short sessions a week. |
When to do cardio
- Best: on separate days, or at least a few hours apart from lifting (for example lift in the morning, bike in the evening).
- Same session? Lift first, then do cardio.
- Protect leg day. Avoid hard or long cardio the day before or right before training legs.
- Upper body days are the easiest days to add cardio after lifting.
Sample week: lifting + cardio
| Day | Training |
|---|---|
| Mon | Upper A + 20 min bike |
| Tue | Lower A |
| Wed | 30–40 min incline walk or easy bike |
| Thu | Upper B + 20 min rowing |
| Fri | Lower B |
| Sat | Long walk or other activity you enjoy |
| Sun | Rest |
Plus daily walking. That's about 90–110 minutes of planned cardio a week without getting in the way of your lifting.
Eat for the extra work
Cardio burns calories. A 30-minute moderate bike session can burn a few hundred, depending on your size and effort. If you're bulking and add cardio without eating more, you may simply stop gaining. Watch your weekly average weight and add 100–200 calories a day if it stalls. See how many calories to build muscle.
Common mistakes
- Skipping cardio completely. Your heart is a muscle too.
- Doing hours of it. More than you can recover from will eat into your gains.
- Hard intervals before leg day. Tired legs mean worse squats.
- Not eating more. The interference effect is often just an energy problem.
- Making it miserable. Pick something you'll actually keep doing.
Frequently asked questions
Does cardio kill gains?
Not in sensible amounts. A 2022 meta-analysis found adding cardio to weight training didn't reduce muscle growth or maximum strength on average. Very high amounts, especially frequent long runs, are what cause problems.
How much cardio can I do without losing muscle?
For most lifters, 2 to 3 sessions of 20 to 40 minutes a week plus daily walking is plenty for heart health and won't hurt muscle growth, as long as you eat enough.
Should I do cardio before or after weights?
After. Lifting first led to better lower-body strength gains in research. Even better, do cardio on separate days or a few hours apart from lifting.
What is the best cardio for building muscle?
Low-impact options like cycling, incline walking, rowing and swimming interfere least. Running is fine in moderation but keep long runs away from leg day.
Should I do cardio when bulking?
Yes. 2 to 3 moderate sessions a week keeps your heart healthy and may limit fat gain. Just eat a little more to cover the calories you burn.
Is HIIT or steady cardio better for lifters?
Both work. HIIT is quicker but more tiring, so keep it to 1 to 2 short sessions a week. Steady cardio like cycling or incline walking is easier to recover from.
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This article is general information for healthy adults and isn't medical advice. If you have a heart condition or other health issue, check with your doctor before starting a new cardio routine. Sources: Schumann et al. (2022), "Compatibility of concurrent aerobic and strength training for skeletal muscle size and function: an updated systematic review and meta-analysis", Sports Medicine. Wilson et al. (2012), "Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises", Journal of Strength and Conditioning Research. Murlasits, Kneffel & Thalib (2018), "The physiological effects of concurrent strength and endurance training sequence: a systematic review and meta-analysis", Journal of Sports Sciences. Konopka & Harber (2014), "Skeletal muscle hypertrophy after aerobic exercise training", Exercise and Sport Sciences Reviews. World Health Organization (2020), WHO guidelines on physical activity and sedentary behaviour. Related reading: Rest days · How to cut without losing muscle · Body recomposition · Upper/lower split · Building muscle over 40