Does cardio kill your gains?

Mostly no. Across 43 studies, people who added cardio to the same lifting program gained as much muscle and as much maximal strength as people who only lifted; the one thing that gained a little less was explosive strength2.

The fear has a real origin, and a few reviews disagree on the details. Below is where the idea came from, what the largest analysis found, and where the answer is still "it depends".

Where the worry came from

Combining lifting and cardio in one plan is called concurrent training. The idea that it holds back strength goes back to a 1980 study1. One group lifted 5 days a week, one did endurance work 6 days a week for 40 minutes a day, and a third did both programs in full.

For the first 7 weeks, the combined group gained leg strength at the same rate as the lifting-only group1. Then their gains levelled off and declined in weeks 9 and 10. Aerobic fitness (VO2max, the most oxygen the body can use during hard exercise) rose about 25% on the bike in both groups that did endurance work.

That became known as the interference effect. It is worth knowing what was combined: a full strength program plus 40 minutes of endurance work 6 days a week, for 10 weeks. That is a large training load.

In plain terms: the original finding was real, but it came from doing two full programs at once.

What the largest analysis studied

The most complete answer is a 2022 meta-analysis, a review that pools the results of many studies2. It included studies of healthy adults, lasting at least 4 weeks and supervised, in which one group did a strength program alone and another did the identical strength program plus aerobic training.

The review looked at three outcomes2:

• Muscle growth (hypertrophy): the size of the trained muscles, measured on scans.
• Maximal strength: the most force a person can produce, such as a 1RM (the heaviest load lifted once).
• Explosive strength: how quickly force is produced, measured with jumps, rapid-force tests or power.

Results are reported as a standardised mean difference (SMD). It expresses the gap between groups in units of the spread between people. Zero means no gap, about 0.2 is small, and a minus sign means the cardio group gained less.

In plain terms: the same lifting program, with and without cardio added, in about a thousand people.

What the studies found

Two of the three outcomes showed no difference2:

• Muscle growth: an SMD of about zero across 15 studies (95% CI −0.16 to 0.18).
• Maximal strength: −0.06 across 37 studies (95% CI −0.20 to 0.09), with no spread between studies beyond chance.
• Explosive strength: −0.28 across 18 studies (95% CI −0.48 to −0.08). That is a small but statistically significant dip.

The explosive-strength dip came mostly from rapid-force and power tests. Jump height alone showed a smaller effect that was not significant2.

The review also checked other factors. Cycling versus running, how often people trained, whether they were untrained or active, and whether they were under or over 40 made no significant difference to muscle growth or maximal strength2.

In plain terms: adding cardio did not reduce muscle growth or top-end strength on average. It slightly reduced gains in how fast force is produced.

Does timing matter?

The review split the explosive-strength studies by how close the cardio was to the lifting2:

• Same session (within about 20 minutes): −0.31 (95% CI −0.62 to −0.01), 8 studies.
• Same day, at least 3 hours apart: +0.08 (95% CI −0.25 to 0.42), 5 studies.
• Different days: −0.35 (95% CI −0.94 to 0.24), 5 studies, with results scattered widely and one study flagged as an outlier.

This is where caution matters. A test comparing the three timing groups was not significant (p 0.288)2. So the data hint that separating cardio from lifting by a few hours may matter for explosive strength, but the review could not show that timing itself is the cause. The authors suggest that people who prioritise explosive strength "may benefit from separating" the two. As a possible mechanism, they "speculated" that fatigue left over from cardio may blunt rapid force production2. That is a hypothesis, not a measured result.

In plain terms: the small dip in explosive strength was clearest when both were done back to back. Whether spacing them out removes it is not settled.

Where other reviews differ

Pooled averages depend on which studies are pooled and how. Two other reviews looked at the same question differently.

By sex. A 2024 meta-analysis of 59 studies with 1,346 adults aged 18 to 50 found concurrent training slightly blunted lower-body strength gains in men (SMD −0.43, 95% CI −0.64 to −0.22) but not in women (0.08, −0.34 to 0.49)3. There was too little data to draw conclusions on muscle growth. Women are under-represented in this research; the 2024 network meta-analysis notes its sample was mostly trained men4.

By type of cardio. A 2024 network meta-analysis of 40 studies with 841 people compared cardio types4. For muscle size, no combination differed clearly from lifting alone. For lower-body maximal strength, moderate running (−0.25, 95% CI −0.46 to −0.05) and moderate cycling (−0.38, −0.62 to −0.14) came out below lifting alone. High-intensity interval training came closest to lifting alone. That disagrees with the 2022 review on maximal strength.

In plain terms: on muscle growth the reviews agree. On strength, the answer shifts a little with who was studied and what kind of cardio they did.

What this means in practice

This is a description of what the studies found, not a cardio prescription:

• Muscle growth held up with cardio added, in every review that could measure it24.
• Maximal strength held up on average in the largest review, with small dips in some subgroups23.
• Explosive strength showed a small cost, clearest with same-session training2.
• Very high combined loads are where the original interference appeared1. How to recognise when total training is piling up is covered in signs of accumulated training fatigue.

How lifting days fit into a week is covered in how many days a week should you lift, and weekly sets per muscle in how many sets per muscle group per week. None of these studies looked at fat loss, which is a separate question.

The studies at a glance

Limits worth knowing

• Short studies. Every study in the 2022 review lasted 4 to 22 weeks. Nothing here covers years of combined training2.
• Medium quality. The average study scored 4.3 out of 10 on a quality scale, and seven were rated low quality2.
• Mostly men. Results for women rest on fewer studies34.
• Cardio amount not analysed. The 2022 review could not test how much or how hard the cardio was, because studies reported it inconsistently2.
• What we read. The 2022 review and the 2024 network meta-analysis in full text; the other three as abstracts.

Latest research

The newest study we opened is a 2026 umbrella review in *Sports Medicine*, a review of reviews5. It pooled 17 meta-analyses covering 144 studies and 1,492 healthy people. Compared with lifting alone, concurrent training produced comparable strength, power and muscle growth, and better aerobic capacity. Training order showed no significant effect, though the authors saw trends favouring lifting before cardio. They note that data from highly trained and elite athletes remain scarce. When larger or longer studies appear, this page will be updated and its date will change.

The short version

• Adding cardio to the same lifting program did not reduce muscle growth across 43 studies.
• Maximal strength held up on average; some reviews found small dips in men or with certain cardio types.
• Explosive strength gained slightly less, most clearly when cardio and lifting shared a session.
• The studies lasted weeks to months, and most were medium quality.

Educational overview only — not medical advice.