Concurrent training is the practice of combining endurance exercise (like running, cycling, or swimming) and resistance exercise (like weightlifting) within the same training program. That program might blend both types into a single workout session or alternate them on different days across a weekly schedule. It’s the default approach for most people who want to be both strong and fit, but the way you structure it matters more than most exercisers realize.
Why Combining Both Types Works
The appeal of concurrent training is straightforward: you get benefits that neither strength training nor cardio can deliver on its own. In a study comparing concurrent training to high-intensity interval training (HIIT) alone and resistance training alone, the combined approach produced significantly greater fat loss (9 kg lost vs. 6.7 kg for HIIT and 6.0 kg for resistance training) and a 12% improvement in estimated cardiorespiratory fitness, roughly double what resistance training alone achieved. These weren’t small differences. The effect sizes were large across body composition, walking endurance, and aerobic capacity.
For the general population, concurrent training is arguably the most practical approach. You build muscle, improve cardiovascular health, and lose fat simultaneously rather than choosing one goal at the expense of another.
The Interference Effect
The tradeoff is something researchers call the interference effect: when endurance and strength training are combined, each can partially blunt the other’s results. A large meta-analysis found that strength development had an average effect size of 1.76 with strength training alone but dropped to 1.44 with concurrent training. Power development took a bigger hit, falling from 0.91 to 0.55. Muscle growth also decreased, going from an effect size of 1.23 to 0.85.
In plain terms, you’ll still get stronger and build muscle with concurrent training, but somewhat less than if you only lifted weights. The same is true on the endurance side, though to a lesser degree for most people.
The interference isn’t random. Two factors consistently predict how much your strength gains suffer: the frequency and duration of your endurance sessions. The more often and longer you do cardio, the more it chips away at hypertrophy, strength, and power. Interestingly, the type of cardio matters too. Running causes more interference with muscle growth than cycling, likely because the repeated impact and eccentric muscle contractions in running create more muscle damage. Swimming appears to cause even less interference than cycling, generating a smaller inflammatory response.
How Your Training Experience Changes Results
If you’re relatively new to exercise, the interference effect is mostly an academic concern. Novices respond robustly to almost any training stimulus, showing significant gains in muscle size, strength, and aerobic fitness even with moderate training loads. Your body has so much room to adapt that the competing signals from cardio and lifting don’t meaningfully cancel each other out.
As you become more advanced, the picture shifts. Trained athletes experience smaller returns from the same effort and need higher training volumes and intensities to keep improving. At that level, the interference effect becomes more relevant because every marginal gain matters, and the fatigue from one type of training can directly limit performance in the other. Advanced athletes also face elevated injury risk from the accumulated training load, which makes programming and recovery even more important.
Structuring Your Program
The biggest lever you can pull is recovery time between sessions. To maximize strength and muscle adaptations, aim for 3 to 6 hours between your endurance and resistance sessions when training on the same day. If your primary goal is endurance, spacing sessions by 24 hours is better. In some cases, separating the two modalities by a full 2 days produces the highest level of adaptation in both areas.
One nuance worth noting: when resistance training comes before endurance training on the same day, the recovery window may need to be longer than 48 hours, particularly for women, who may experience greater fatigue from the combined demand.
Beyond session spacing, a few practical guidelines consistently emerge from the research:
- Limit endurance frequency. Keep cardio sessions to no more than 3 days per week if your priority is minimizing interference with strength gains.
- Choose low-impact cardio. Cycling causes less interference than running. Swimming may be even gentler. If you don’t need to train running specifically, a stationary bike is the safer choice for preserving muscle growth.
- Fuel recovery with protein. Consuming 20 to 40 grams of protein shortly after a session supports muscle protein synthesis and helps offset the competing demands of concurrent training. This is especially important when sessions are close together.
Exercise Order Within a Session
A common question is whether you should lift before or after cardio when doing both in one session. The research here is less definitive than you might expect. Some studies show a slight advantage to doing resistance work first, since fatigue from prior cardio can reduce the weight you’re able to lift. But at least one study found that concurrent training improved lower-body strength and lean mass comparably to resistance-only training regardless of exercise order.
The practical takeaway: put whichever type of training is more important to your goals first, when you’re freshest. If you’re primarily trying to get stronger, lift first. If you’re training for a race, do your endurance work first. When both matter equally, starting with resistance training is a reasonable default since strength and power are more sensitive to fatigue than aerobic work.
Nutrition for Concurrent Training
Concurrent training places higher total demands on your body than either modality alone, which makes nutrition more consequential. The general framework that supports combined training is a diet with at least 50% of calories from carbohydrates, 10 to 15% from protein, and 30 to 35% from fat. Carbohydrate intake is especially important because both endurance exercise and resistance training rely heavily on glycogen stores, and chronically low carbohydrate availability amplifies the interference effect by keeping your body in an energy-depleted state.
Post-workout protein deserves specific attention. A randomized, double-blind trial found that consuming 40 grams of whey protein after concurrent training sessions increased adaptations compared to a calorie-matched placebo in previously untrained adults. The protein group saw greater improvements in both strength and body composition. If you’re doing concurrent training, a protein shake or a protein-rich meal within a short window after your session is one of the simplest things you can do to support your results.