Cardio and Strength: Why You Need Both, Not One or the Other

Fitness culture loves a camp. You're a runner or a lifter, a cardio person or a weights person, and each side has a story about why the other is a waste of time: cardio "kills your gains", or lifting makes you "bulky and slow". It's an entertaining debate, and it doesn't hold up well against the research. When you look at what actually predicts long-term health, and at what happens when people train both qualities together, the answer is consistent: you need both, and they get along much better than the myths suggest.

This isn't a plea to do everything at once. It's about understanding what each type of training gives you that the other can't, and then arranging them sensibly so that each supports the other rather than competing for the same recovery.

What Aerobic Fitness Gives You

Cardiorespiratory fitness, your heart, lungs and circulation's capacity to deliver and use oxygen, is one of the strongest single predictors of long-term health. A landmark meta-analysis by Kodama and colleagues (2009), published in JAMA, pooled data from studies of healthy men and women and quantified the relationship. Each 1-MET increase in fitness (a MET is a unit of exercise capacity, roughly the energy cost of sitting quietly) was associated with a 13% lower risk of death from any cause and a 15% lower risk of coronary heart disease and cardiovascular events.

That's a large effect from a quality that responds well to training at any age. Aerobic work also underpins recovery between hard efforts, supports healthy blood pressure and metabolic health, and simply makes daily life feel easier. Anyone who has taken up lifting after years of inactivity and found themselves out of breath between sets knows how much your aerobic base affects even strength training.

What Strength Training Gives You

Muscle-strengthening activity brings benefits that aerobic training doesn't fully cover. A 2022 systematic review and meta-analysis by Momma and colleagues, published in the British Journal of Sports Medicine, pooled prospective cohort studies following adults over time. Muscle-strengthening activity was associated with a 10–17% lower risk of all-cause mortality, cardiovascular disease, total cancer, diabetes and lung cancer. The relationship wasn't linear: the largest benefit for mortality appeared at around 30 to 60 minutes a week, with no clear additional benefit beyond that in the data available.

Strength training also protects the things aerobic training tends to neglect: muscle mass, bone density, tendon resilience, and the ability to produce force quickly. Those qualities matter more with every decade, as they are the difference between catching yourself in a stumble or falling, and between carrying your own shopping or needing help.

The Combination Beats Either One Alone

The most striking finding in the Momma meta-analysis was what happened when the two were combined. In the studies that looked at both, people who did muscle-strengthening and aerobic activity together had a lower risk of death than those who did either alone; the authors reported roughly a 40% lower all-cause mortality risk for the combination compared with doing neither.

The World Health Organization builds its recommendations on the same principle. The 2020 WHO guidelines, summarised by Bull and colleagues in the British Journal of Sports Medicine, recommend that adults do at least 150 to 300 minutes of moderate-intensity (or 75 to 150 minutes of vigorous) aerobic activity each week, and muscle-strengthening activities involving all major muscle groups on two or more days a week. Both, not either.

What About the Interference Effect?

The main reason people avoid combining the two is the "interference effect": the idea that endurance training blunts the gains from strength training. It is a real phenomenon, but it's smaller and more specific than gym folklore suggests.

An early meta-analysis by Wilson and colleagues (2012), published in the Journal of Strength and Conditioning Research, found that interference depended on the details. It was associated with the type, frequency and duration of the endurance work. Running appeared to interfere more with lower-body strength and muscle gains than cycling did, and higher volumes and frequencies of cardio were more likely to cause problems.

A more recent and larger update by Schumann and colleagues (2022) in Sports Medicine found that concurrent training did not compromise gains in muscle size or maximal strength compared with strength training alone. The one quality that was consistently blunted was explosive strength, the ability to produce force very quickly, and this effect was more pronounced when both types of training were done in the same session.

For most people training for health, body composition and general performance, that's reassuring: you can build strength and muscle while also building your aerobic engine. The trade-offs mainly matter at the extremes, for power athletes chasing every last bit of explosiveness, or endurance athletes carrying very high training volumes.

How to Combine Them Well

Separate the sessions when you can

Since interference is greater when both are done together, putting strength and hard cardio on different days, or at least several hours apart, is the simplest way to reduce it. If they have to share a session, do the one that matters most to your goals first.

Choose lower-impact cardio around leg days

Cycling, rowing and incline walking tend to interfere less with lower-body strength than lots of running does. If you're a runner, that's not a reason to stop running. It's a reason to avoid placing your hardest runs right before or after heavy leg sessions.

Build the aerobic base mostly at easy intensity

Much of your cardio can be done at a conversational pace, which builds aerobic fitness without heavy fatigue. Save one or two harder sessions a week for higher-intensity work, and schedule them away from your heaviest lifting days.

Match the balance to your goal

A marathon runner and a strength athlete shouldn't have the same week. But both benefit from the other quality: runners from two strength sessions a week, lifters from two or three aerobic sessions. The ratio changes; the principle doesn't.

Strength keeps you capable. Aerobic fitness keeps you going. The research is clear that the people who do both come out ahead of the people who pick a side.

A Sample Week That Covers Both

Here's one simple way to arrange a week for someone training four or five days, with the interference research in mind:

• Monday: Full-body strength session (squat or deadlift pattern, a push, a pull, a loaded carry).
• Tuesday: 30 to 45 minutes of easy aerobic work, such as cycling, rowing or an easy run at a conversational pace.
• Wednesday: Rest, or a walk and some mobility work.
• Thursday: Full-body strength session with different variations from Monday.
• Friday or Saturday: One harder aerobic session, such as intervals, placed at least a day away from heavy leg work, plus a longer easy session on the other day if time allows.

That structure hits the WHO's two strength days and gets most people into the recommended aerobic range, while keeping the hardest efforts apart. Adjust the balance towards whichever quality your goal depends on most.

Starting From Zero

If you currently do neither, the combination can sound like a lot. It doesn't have to be. Two full-body strength sessions and two or three 30-minute brisk walks, rides or easy runs each week is a realistic starting point that already covers the core of the WHO recommendations. Build consistency first, then gradually increase the volume or intensity of whichever quality is furthest behind.

If you've been in one camp for years, the fastest wins usually come from adding a small dose of the other. Lifters who add easy cardio often find they recover faster between sets and sessions. Runners who add strength work often find they get injured less. Both are signs that the two qualities work together far better than they compete.

FAQ

Will cardio kill my strength and muscle gains?

For most people, no. An updated meta-analysis by Schumann et al. (2022) found that concurrent aerobic and strength training did not compromise gains in muscle size or maximal strength. Explosive strength was somewhat blunted, mainly when both were done in the same session, so separating them helps.

How much strength training do I need for health benefits?

Momma et al. (2022) found the greatest reduction in mortality risk at around 30 to 60 minutes of muscle-strengthening activity per week. The WHO 2020 guidelines recommend strength training for all major muscle groups on at least two days per week, alongside 150 to 300 minutes of moderate aerobic activity.

Should I do cardio before or after weights?

Prioritise whichever matters most to your goal. If strength is the priority, lift first; if endurance is the priority, do the cardio first. Where possible, separate them by several hours or put them on different days, since interference appears greater when both are done in the same session.

Sources

• Kodama, S., Saito, K., Tanaka, S., et al. (2009). Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: A meta-analysis. JAMA, 301(19), 2024–2035.
• Momma, H., Kawakami, R., Honda, T., & Sawada, S. S. (2022). Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: A systematic review and meta-analysis of cohort studies. British Journal of Sports Medicine, 56(13), 755–763.
• Bull, F. C., Al-Ansari, S. S., Biddle, S., et al. (2020). World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British Journal of Sports Medicine, 54(24), 1451–1462.
• Wilson, J. M., Marin, P. J., Rhea, M. R., et al. (2012). Concurrent training: A meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research, 26(8), 2293–2307.
• Schumann, M., Feuerbacher, J. F., Sünkeler, M., 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, 52(3), 601–612.