Training for it all: what 36 studies say about combining cardio and weights

The shift that is changing gyms: training for everything

Walk into any gym and you'll see people who no longer pick a side. Some used to only run and now lift weights; others used to live on squats and now finish with 20 minutes on the bike. And they are not doing it because it is trendy, but because they have found out something they were told for years would not work.

In 2018, around 600 people took part in the first edition of Hyrox, a competition that mixes running with strength exercises. In 2025, that figure passed 550,000 participants a year, spread across more than 80 races in 30 countries. That's not a small detail, it's proof that the idea of training for everything has stopped being a thing for elite athletes and has become what the regular person at the gym wants to do with their body.

Science has given this a formal name: concurrent training. And it has spent years building evidence that combining strength and cardio does not hold you back, and in many cases gives you better results than doing only one of the two. In May 2025, a team of researchers at the University of South Florida published a wide-ranging review on this subject. They pulled together 36 studies with 1,564 people and compared what happens when you do only cardio, only weights, or both together. The results are clear and worth understanding properly.

36 studies and 1,564 people: what this review says about strength, cardio and body composition

The meta-analysis was led by Kworweinski Lafontant and published in the Journal of the International Society of Sports Nutrition. The researchers searched three databases (PubMed, SportDiscus and Web of Science) for every controlled clinical trial published between January 1980 and January 2023 that compared three types of training in healthy adults: strength training alone, aerobic training alone, or the two combined.

Of the 36 studies included, 31 had enough data for the statistical analysis. The main question was direct: when it comes to losing body fat, gaining or holding on to muscle and changing your body composition, which approach wins?

Before looking at the numbers, there is something important to understand. Reviews like this one don't look at a single study, they pool data from many studies and work out a general trend. That means not every study says exactly the same thing, but the direction of the whole is what matters. And in this case, the direction was consistent.

Losing fat: where cardio and the combination beat weights alone

When the researchers analyzed the studies that ran for 10 weeks or more, they found two significant results on fat loss.

First: the people who did only cardio lost on average 1.06 kilos more fat than those who did only weights. The difference was statistically significant, with a 95% confidence interval between 0.24 and 1.88 kilos.

Second: the people who combined strength and cardio also lost more fat than those who did only weights. The difference was 1.09 kilos in favor of the combined group, with a confidence interval between 0.27 and 1.91 kilos.

These numbers may look small, but they need context, because we're talking about an average across people of different ages, fitness levels and training protocols. The fact that the trend holds across so many studies is what gives the result its weight.

One figure surprises a lot of people: there were no significant differences in body fat percentage between the three approaches. That seems to contradict the above, but there is a logical explanation. Body fat percentage depends on two variables: how much fat you carry and how much muscle you carry, and if you lose fat but gain muscle, the percentage can barely move even though your body has changed a lot. And that is exactly where the most interesting finding in the study comes in.

The argument that changes the conversation: protecting your muscle

The group that did only cardio lost more total weight than the one that lifted: 1.82 kilos on average. But part of that weight was not fat. It was muscle.

The people who did only aerobic exercise held on to 0.88 kilos less fat-free mass than those who lifted. Put another way: cardio helps you lose weight, but part of what you lose is the tissue you most want to keep.

This isn't a technical detail, it's the difference between losing 5 kilos and looking better, or losing 5 kilos and looking the same but smaller. Muscle is what gives your body its shape, what keeps your metabolism active and what protects you as you age. Losing it is not a minor side effect.

This is where combined training shows its real advantage. Lafontant's data show that adding strength to cardio did not slow fat loss across the pooled data. Zero interference, and it did help hold on to muscle. In other words: combining gives you the best of both worlds. You lose fat as if you were doing cardio, but you keep muscle as if you were lifting.

The researchers put it clearly: "Resistance training neither improved nor prevented fat loss when it was incorporated into concurrent training." Translated: adding weights to your cardio routine does not make you lose less fat. It makes you lose the same fat and keep more muscle.

Does the length of the program matter? The 10 week threshold

An important finding of the meta-analysis is that the length of the program makes a real difference: in studies that ran for less than 10 weeks, there were no significant differences between the three training approaches. Your body needs time to show measurable changes in body composition, and the first weeks are mostly neurological adaptation and habit.

From 10 weeks on is when the differences start to appear. That has a direct practical implication: if you have spent 4 or 6 weeks combining strength and cardio and you see no change in the mirror, do not quit. The data say the real changes come later. Patience isn't an abstract virtue here, it's a variable that decides whether your plan works or not.

There is another conclusion from the study worth mentioning: when the researchers compared studies where total work volume was matched between groups, the differences between approaches disappeared. In other words, if you do the same total amount of effort, it does not matter how you split it up. What changes the outcome is not so much the type of exercise as the total amount you do and how many weeks you keep it going.

Men and women: does cardio affect your strength gains differently?

One of the most widespread fears about combining strength and cardio is what researchers call the interference effect: the idea that doing cardio blocks strength gains. It's a fear that has kept a lot of people away from cardio for years, but put to the test, that fear turns out to be overblown.

In February 2025, a study published in the Scandinavian Journal of Medicine and Science in Sports tested this idea with 96 people (56 men and 40 women) over 12 weeks. The researchers, led by Feuerbacher, split the participants into three groups: one did HIIT and strength on the same muscle groups, another separated the HIIT (lower body) from the strength work (upper body), and a third did strength only.

The result was clear: no sex-based differences were seen in any of the measurements. Not in maximal strength (squat and bench press 1RM), not in explosive power, not in muscle hypertrophy. Men and women responded to concurrent training the same way.

But the most important part was the study's overall conclusion: concurrent training did not harm explosive strength, maximal strength or muscle hypertrophy, whether the same muscle groups were worked or different ones. Squat 1RM improved significantly in every group that included lower-body strength work. The cross-sectional area of the vastus lateralis (the muscle at the front of the thigh) actually grew more in the group that combined HIIT and strength on the same muscle group than in the strength-only group.

What does this mean in practice? Whether you are a man or a woman, you can combine strength and cardio without fearing for your strength gains. The 2025 evidence found no measurable negative effect. And if you were worried that doing HIIT on your legs would hurt your squat, the data say no: your strength and your muscle grow just the same.

If you are just starting: why progression matters more than the perfect structure

If you have never combined strength and cardio, there is something practical experience confirms over and over: you do not need to find the perfect structure before you start. You need to start and adjust as you go.

The body of someone who has not trained for a while needs to adapt to any new stimulus. If you give it two very different stimuli at once (heavy lifting and hard cardio) and at high volume, they will compete for the same recovery resources. The result is excessive fatigue, a plateau or an injury.

The practical takeaway: if you are starting out, bring the combination in gradually. Begin with modest volumes in both (for example, 2 short strength sessions and 1 of moderate cardio) and build up over the weeks. Your body will adapt and its capacity to handle both stimuli will improve. There is no rush. What matters is that you start with both, even in small doses.

If you only do cardio: what the data say you are missing

If you have spent months or years on the treadmill, the bike or the elliptical and nothing else, Lafontant's results are especially relevant to you. Cardio is excellent for heart health, for mood and for burning calories. Nobody argues with that. But when it comes to changing the shape of your body, it has a ceiling.

The most relevant figure: the cardio-only group kept less of its fat-free mass than the weights group did. Those 0.88 kilos of difference in fat-free mass compared with the weights group may look like little, but stacked up over years they add up to a real functional loss. Less muscle means a slower metabolism, less strength for daily tasks, less bone density and a body that ages faster.

From the age of 30 on, the body loses muscle mass naturally unless it gets a strength stimulus, and that process, called sarcopenia, picks up speed after 50. Cardio doesn't slow it down, weights do. So if you only do cardio and you're past 35, you aren't doing anything wrong, you're just missing the other half of the plan.

Adding two strength sessions a week takes away nothing that cardio gives you. The data from this meta-analysis confirm it: combined training gives results that match or beat cardio alone for fat loss, and beat it for keeping muscle. You are not sacrificing anything. You are adding.

If you only lift: what the data say you are missing

The other end of the spectrum has clear data too. If you live on squats and bench press but do no cardio at all, Lafontant's numbers show that the strength-only group lost less fat than the combined group in programs longer than 10 weeks. The difference was 1.09 kilos. Not huge, but significant.

Beyond the body composition numbers, there is a health argument the meta-analysis does not measure but the general evidence backs strongly: the heart needs aerobic work. Cardiovascular fitness is one of the strongest predictors of death from any cause. You can be the strongest person in your gym, but if you are out of breath after two flights of stairs, your heart is not getting what it needs.

The fear of losing gains by doing cardio is real but out of proportion. Feuerbacher's study with 96 people over 12 weeks found no significant difference in maximal strength or hypertrophy between those who combined and those who only lifted. Two or three moderate cardio sessions a week are not going to wreck your strength progress. They are going to improve your recovery between sets, your work capacity and your long-term heart health.

How to organize your week if you want to train for everything

There is one finding in Lafontant's meta-analysis that makes planning much simpler: there were no significant differences between doing strength and cardio on the same day or on separate days. In other words, what works is combining, and how you split it up matters far less.

That said, there are details worth knowing. A semi-systematic review published in January 2026 in Frontiers in Sports and Active Living, which analyzed 42 studies in humans and in animals published between 1980 and 2024, confirmed that when you do cardio and strength on the same day, it pays to separate the sessions by at least 3 hours. The reason is biological: aerobic and strength exercise switch on different metabolic pathways in your muscles, and when they overlap in time they compete with each other and each signal arrives muffled. Separate them by at least 3 hours and each signal has room to do its job without interference.

In practice, the simplest structure for someone with 4 days available is to alternate: one strength day, then a cardio day, rest, and repeat. That way every session starts with a fresh body and no leftovers from the previous stimulus.

If you only have 3 days, give 2 to strength (full body) and 1 to cardio. Or, if endurance is your priority, do 2 of cardio and 1 of strength. The key is that both show up in your week regularly.

If you would rather combine them in the same session, put first whatever matters most to you. If your main goal is strength, start with weights and finish with 15 to 20 minutes of moderate cardio. If your goal is endurance, do it the other way around. Performance always drops in whatever you do second, so give priority to what you most want to improve.

Cardio intensity matters more than you think

Not all cardio interferes with strength in the same way. That same 2026 review in Frontiers in Sports and Active Living found something interesting about HIIT: when it was combined with strength work on the same muscle group, maximal strength and hypertrophy were unaffected. But it did detect that doing HIIT right before lifting reduced jump power and the quality of the strength session that came immediately after. In other words: HIIT does not ruin your long-term adaptations, but it can make your strength session worse on the same day.

The review also pointed out that starting with strength and doing the cardio afterward is more favorable for neuromuscular adaptations, improving relative strength and explosive power. If your main goal is building strength, that order (weights first, cardio second) keeps the impact on the quality of your strength work to a minimum.

In practice this comes down to something simple. If you do both on the same day, start with what matters most. If strength is your priority, begin with weights and finish with 15 to 20 minutes of moderate cardio. And if you can split them across different days, each session performs at its best because it does not have to compete with the other.

Why does this matter more as the years go by?

There is an argument for combining that does not appear in Lafontant's meta-analysis but that the general evidence backs strongly: age changes the rules of the game. From the age of 30, the body starts losing muscle mass naturally unless it gets a proper strength stimulus. This process, called sarcopenia, speeds up after 50 and keeps shaving muscle mass off decade after decade if you do nothing about it.

Cardio on its own does not stop sarcopenia. What stops it is strength training. And what protects your heart in the long run is cardio. If you are over 35 and you only do one of the two, it is not that you are doing something wrong. It is that you are missing half the plan your body needs to age well.

Combining strength and cardio in middle-aged and older people brings benefits that go well beyond looks. More muscle means more capacity for daily tasks, less risk of falls, better bone density and a more active metabolism. Better cardiovascular fitness means less risk of heart disease, better blood pressure control, better metabolic health and more energy. It is not about choosing which one matters more to you. It is about realizing that you need both.

Eating when you combine: the basics you cannot ignore

Combining strength and cardio asks more of your body than doing only one of the two. You do not need a complicated diet, but you do need to cover the basics. And the basics start with protein.

If you train strength and endurance several times a week, your body needs more protein than if you did not train. Consensus recommendations in sports nutrition put intake between 1.4 and 2.0 grams per kilo of body weight per day when the goal is keeping or gaining muscle while training. If you weigh 75 kilos, that is between 105 and 150 grams of protein a day. It is not an impossible amount, but it takes attention. Chicken, fish, eggs, legumes, dairy, tofu: the source matters less than the total.

Total calories matter too. If your goal is losing fat, you need a moderate calorie deficit, but not one so aggressive that it compromises your performance or your recovery. A deficit of 300 to 500 calories a day is usually enough to lose fat without losing muscle, especially when you combine both types of training. If your goal is improving performance without losing weight, eat to hold your current weight and make sure protein is covered.

Hydration and sleep are the other half of the equation that many people ignore. Training more means recovering more. If you do not sleep 7 to 8 hours, everything you do at the gym pays off less. This is not generic advice. It is a variable that directly affects strength adaptations and cardiovascular capacity.

Which order should the two go in across your week? Strength and cardio in the same week: the structure that works best according to the evidence.

Training for everything is not an athlete thing. It is the smart way to be fit

The idea of the hybrid athlete may sound like social media marketing, but what sits behind it is common sense backed by data. You do not need to compete in Hyrox to benefit from combining strength and cardio. You just need to accept that your body was built for both and that depriving it of one has consequences.

The 36 studies in Lafontant's meta-analysis, the 96 participants in Feuerbacher's and the 42 studies in the 2026 Frontiers in Sports and Active Living review all point the same way: combining strength and endurance gives better results than picking a side. You lose more fat, you keep more muscle, and you build a body that works well for real life.

That means climbing stairs without gasping, carrying the grocery bags without trouble, having energy at the end of the day and feeling capable in any physical situation life puts in front of you. That is training for everything. And the data say it works.

What you can change this very week

You do not need a 12-week plan to start. If you only do cardio, add 2 strength sessions this week. They do not have to be long: 30 to 40 minutes on machines or with bodyweight, working the main muscle groups. They will not cost you your cardiovascular base. They will help you keep your muscle and improve how your body responds to training.

If you only lift, add 2 moderate cardio sessions. Twenty to 30 minutes on the bike, treadmill or elliptical at a pace that still lets you hold a conversation with some effort. They will not cost you strength. They will improve your recovery capacity, your heart health and your general performance.

If you already combine but with no order to it, try separating the stimuli into different days for a month. Strength one day, cardio the next. Compare how you feel and how you progress against the weeks when you mixed everything into every session.

The data are clear. The trend is real. And it does not require changing your life, just dropping the habit of picking a side.

At Gym Triple X you have a weight room and a cardio area to do this without complicating your life. The team is ready to guide you if you do not know where to start or if you need to adjust what you are already doing. Training for everything is not a passing fad. It is common sense backed by 36 studies, 1,564 people and a message that runs through all of them: your body works better when you give it the two stimuli it needs.

If you made it this far, the topic hits close to home. When that happens, it sometimes pays to stop improvising and talk to a personal trainer on the Costa del Sol. Not forever, just to start properly.