Should Skinny Guys Do Cardio? Balancing Cardio and Muscle

By Pete Sullivan · Published September 9, 2026

Yes, skinny guys should do cardio, and the pooled research does not show that adding cardio automatically destroys muscle gains. The directly measurable practical issue this article covers is the energy you use during cardio, which is something you can plan around.

Here is the short version. Do some cardio for your heart and your health, and separate it in time from your lifting where you can. Eat back the calories you burn, then judge the result by the scale and the weights rather than by fear.

What the research actually found

The important thing is that “gains” is not one outcome. Researchers measure at least three separate things, and the evidence treats them differently.

Muscle size (hypertrophy). This is simply how big the muscle gets. An updated systematic review and meta-analysis in Sports Medicine pooled the studies on combining aerobic and strength training. It did not detect a statistically significant reduction in muscle size compared with strength training alone.

Maximal strength. This is the most weight you can move for a single rep, and the same review did not detect a significant reduction there either.

Explosive strength. This is power, meaning how fast you can produce force, as in jumping or sprinting. This is the outcome that took a measurable hit. The review reported that explosive strength gains were attenuated, meaning reduced rather than erased.

One caution matters here, and most articles skip it. A result that is not statistically significant is not proof that the effect is zero. It only means the pooled evidence did not show a drop, which is a weaker claim. So the fair reading is that the popular fear is not supported, not that cardio has been proven safe for every outcome.

Whether that measured cost matters to you depends on your own goals. If you train to add size and get stronger, the affected outcome is not the one you are after. If you play a sport built on jumping or sprinting, it may well be.

The two things that decide how much it matters

Two variables came up repeatedly, and they are the ones worth acting on.

Separation in time, not order. In the Sports Medicine review, the loss of explosive strength was larger when the aerobic and strength work shared a session than when the sessions were at least 3 hours apart.

A second 2021 meta-analysis in the same journal looked at lower-body maximal strength and found a sharper version of the same pattern in its trained group. There the effect was stronger within a single session than when the two were split up, and the authors advise trained people to leave more than 2 hours between them.

Order is a different question, and it is unsettled. The first review reported no evidence for an order-specific effect. It described the cost to explosive strength as coming from training the two close together, whichever came first.

So “always lift first” is a gym rule, not a finding. The cited reviews support separating the sessions where that is practical, but they do not establish an ideal cardio dose for a shared session, and neither does this article.

How trained you already are. The second review split people by training status, and the split matters. Untrained participants showed no significant negative effect. Moderately trained participants showed no significant negative effect. Only the already-trained group showed a small significant negative effect on lower-body strength, and the timing result above belongs to that group.

Read those definitions before you place yourself in one. They are about activity history and nothing else. In that review, untrained meant sedentary, or no regular physical activity for at least 3 months before the study. Moderately trained meant active in a casual way, but not following a set training programme over that same window. Trained meant athletes, or people who had followed a set programme for at least 3 months.

Note what that does and does not mean. Being new to lifting does not put you in the untrained group by itself. If you are new to weights but run regularly, you match the moderately trained description instead. Body size was not part of the grouping, and neither was being skinny, so neither one tells you which group fits you.

Both reviews come with limits worth naming. The Petré review notes that most included studies lasted under 12 weeks, sample sizes were often small, and women were underrepresented. The Schumann review reports modest average study quality and inconsistent reporting that prevented some moderator analyses. Neither review studied underweight or hard-to-gain men as a distinct group. Treat these findings as general direction, not as a dose calculated for you.

The part nobody mentions: the calories

For a skinny guy, this is the practical cost, and it has nothing to do with interference.

Gaining weight runs on a calorie surplus. Cardio spends calories, so if you add a session and do not add food, you have quietly cut your surplus. That is arithmetic rather than physiology, and it is easy to blame on cardio ruining gains.

The CDC publishes rough estimates for a 154-pound person. Running or jogging at 5 mph uses about 295 calories in 30 minutes. Cycling faster than 10 mph is about the same. Walking at 3.5 mph is closer to 140 calories per 30 minutes. The same page notes that heavier people burn more and lighter people burn less, so treat these as ballpark figures rather than your numbers.

On those estimates, three half-hour runs a week comes to roughly 900 calories to replace across the week. That sits on top of your existing target, not inside it. Run yours through the calorie surplus calculator, then add the cardio on top. If eating that much already feels hard, the tactics in how to eat more without feeling sick are worth trying before you cut the cardio.

So how much cardio should you do?

There is no single amount that is right for everyone, and the research does not provide one for this reader. General adult guidance from the CDC is 150 minutes of moderate-intensity activity a week, or 75 minutes of vigorous, plus at least 2 days of muscle-strengthening work covering all the major muscle groups. If your lifting already hits all those muscle groups twice a week, it is covering that second part.

The CDC also notes that some activity is better than none, and that you can break the weekly total into smaller chunks.

This article cannot determine the right starting amount from body size alone. Use the published targets as the general destination, then monitor whether the plan fits your food intake, existing activity and lifting schedule.

The layout below is one gradual starting example, not a prescription, and neither cited review tested this exact schedule. It keeps most sessions off lifting days, which is the separation the reviews point at.

Be clear about its size. Two or three sessions of 20 to 30 minutes comes to roughly 40 to 90 minutes a week. That sits below the general target of 150 moderate minutes, unless you get aerobic activity elsewhere, such as walking to work. Treat it as a start you can build up from, toward the general guideline, as your food, training and recovery allow.

• Lift 3 days a week, following something like the at-home muscle plan or a full-body gym routine.
• Add 2 or 3 easy cardio sessions of 20 to 30 minutes, on non-lifting days where possible.
• Keep most of it easy. Walking, cycling and steady jogging all count.
• Add the burned calories back as food.
• Weigh yourself weekly and adjust from what actually happens.

A simple review checklist

This is not a diagnostic tool, and none of it is a sign of anything on its own. It is a set of questions about your own plan that only you can answer. Run through it when you want to know whether the current setup is working:

• Is your weekly weight trend moving? Compare weekly averages over time rather than single days.
• Is the cardio making your planned food intake harder to complete? You know whether you are hitting your target.
• Are you completing your scheduled lifting sessions and the progress you planned?
• Is the total workload something you can keep doing?

If the weight trend is not moving, the food side is worth checking first, because a surplus is what the plan depends on. That is a starting point rather than a rule, and it will not be the answer for everyone.

If eating more is truly not possible right now, cutting back to 1 or 2 easy sessions and checking again is a reasonable adjustment to try. If your lifts are stuck for reasons that have nothing to do with cardio, work through the six reasons you are lifting but not growing. Anything that feels like a health problem, or any symptom that worries you, belongs with a doctor rather than a website.

The bottom line

Cardio is not the enemy of your bulk. The Schumann review did not detect a significant reduction in muscle size or maximal strength, but it did find explosive strength attenuated, especially when cardio and lifting shared a session, without finding an order-specific effect. The Petré review separately found a small significant negative effect on lower-body maximal strength in already-trained people, which is why training history and session spacing matter. Failing to replace the energy used during added cardio is one common practical reason a planned surplus quietly disappears.

Keep the cardio, separate it from your lifts where you can, and feed it. For more on turning a surplus into muscle, start at the training hub, and if the scale has never moved for you, why you cannot gain weight is the place to begin.

Frequently asked questions

Will cardio cancel out my muscle gains?

The pooled research does not show that. An updated meta-analysis did not detect a statistically significant reduction in muscle size or maximal strength when aerobic training was added to strength training. Explosive strength was the outcome that was attenuated, and more so when both were trained in the same session. A result that is not significant is not proof of no effect, but it is a long way from the claim that cardio cancels your gains.

How much cardio should a hardgainer do?

No single number fits everyone, and the research does not supply one for this reader. The general adult guidance from the CDC is 150 minutes of moderate activity a week, or 75 minutes of vigorous, plus at least 2 days of muscle-strengthening work. The example below starts at 40 to 90 moderate minutes a week and does not claim to satisfy the full guideline. The CDC says some activity is better than none, so it can be used as a gradual starting point while you work toward the general target.

Should I do cardio before or after lifting?

The evidence does not settle the order. The pooled analysis in the Schumann review reported no evidence for an order-specific effect, and described the explosive strength cost as arising from training the two in close proximity regardless of order. What the reviews do point at is separation in time rather than sequence, so if you can put them in different sessions, do that.

Do I have to eat back the calories I burn?

If you want the scale to keep moving, plan for it. Gaining weight depends on a calorie surplus, so a session you add is energy you have to replace on top of your existing target. Adding a 300-calorie run without adding food shrinks the surplus you were relying on, and that is one common reason a planned surplus quietly disappears.

Sources

1. Schumann M et al., Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis, Sports Medicine (2021): Pooled analysis did not detect a statistically significant interference effect on muscle hypertrophy or maximal strength compared with strength training alone, reported attenuated explosive strength, found that attenuation more pronounced within the same session than when sessions were separated by at least 3 hours, and reported no evidence for an order-specific effect.
2. Petré H et al., Development of Maximal Dynamic Strength During Concurrent Resistance and Endurance Training in Untrained, Moderately Trained, and Trained Individuals: A Systematic Review and Meta-analysis, Sports Medicine (2021): Found a small significant negative effect on lower-body maximal dynamic strength in already trained participants only, with no significant negative effect in untrained or moderately trained participants, and reported the interference in trained participants was stronger within the same session than when separated, with the authors advising trained individuals separate the two by more than 2 hours.
3. CDC, Adult Activity: An Overview: Adults are advised to get 150 minutes of moderate-intensity physical activity a week, or 75 minutes of vigorous-intensity activity, plus at least 2 days of muscle-strengthening activity covering all major muscle groups, and that some activity is better than none.
4. CDC, Physical Activity and Your Weight and Health: Published estimates of the calories a 154-pound person uses in 30 minutes of common activities, including running or jogging at 5 mph and cycling faster than 10 mph, with the stated caveat that heavier people burn more and lighter people burn less.
5. MedlinePlus, Obesity: States that taking in more calories than your body uses can lead to obesity, because the body stores unused calories as fat, which is the energy-balance premise behind gaining weight on a calorie surplus.
6. CDC, Benefits of Physical Activity: States that getting at least 150 minutes a week of moderate physical activity can put you at a lower risk for heart disease and stroke, and that physical activity has immediate and long-term benefits, helping you feel better, function better and sleep better.