For many people in the gym, cardio is either seen as punishment or avoided completely. Some believe it will harm their gains or burn muscle, while others use it excessively, hoping it will magically accelerate fat loss. The truth sits somewhere in the middle: cardio is a very powerful tool when used correctly. It improves health, supports training performance, and can even help with body composition — but like anything in training, it has to be applied correctly and consistently.
Let’s take a look at what cardio actually does and how to use it depending on your goals.
What Cardio Actually Improves
Cardiovascular training does a lot more than just burn calories. It helps creating a wide range of physiological adaptations that can benefit both health and performance.
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Cardiovascular Health
Cardio strengthens the heart and improves circulation. Over time, this leads to better blood flow, lower resting heart rate, and improved oxygen delivery throughout the body. These adaptations are one of the main reasons regular cardiovascular exercise is strongly associated with a lower risk of heart disease and improved long-term health and well-being.
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VO₂ Max and Aerobic Capacity
Cardio improves your VO₂ max, which is basically your body’s ability to utilize oxygen as you exercise. A higher VO₂ max means your body can produce energy more efficiently, especially during prolonged or repeated efforts. At the end of the day, this means better work capacity and improved endurance.
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Reduced Fatigue During Workouts
Better aerobic conditioning can make resistance training feel less exhausting. When your cardiovascular system is more efficient, you recover faster between sets and accumulate less fatigue during training sessions. That leads to more productive workouts and better long-term progression.
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Improved Metabolic Health
Cardio improves insulin sensitivity and overall metabolic function. This can help your body regulate blood sugar more effectively and make it easier to improve body composition over time. It also contributes to better nutrient partitioning — your body uses whatever you eat way more efficiently.
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Increased Recovery and Blood Flow
Low to moderate intensity cardio can improve recovery by increasing circulation and promoting nutrient delivery to tissues. This is why light cardio is a great pick on rest days to support active recovery.
Choosing the Right Type of Cardio
Not all cardio serves the same purpose. The type, intensity, and duration should always support your primary goal. A simple way to gauge intensity is by using the percentage of your maximum heart rate (HRmax).
A rough estimate of HRmax is: 220 – age (This is not 100% perfect, but good enough for practical use.)
Low-Intensity Cardio (LISS) ~50–65% of max heart rate
Examples: walking, cycling, and incline treadmill, light rowing.
Primary fuel: mostly fat oxidation, with some carbohydrate use.
Benefits:
- Supports recovery
- Low fatigue cost
- Easy to maintain consistently
This type is ideal for general health, recovery days, and maintaining energy expenditure.
Moderate Intensity Cardio ~65–80% of max heart rate
Examples: steady-state running, rowing (more intense), longer bike sessions.
Fuel mix: both carbohydrates and fats contribute significantly.
Benefits:
- Improves aerobic capacity
- Builds endurance
- Moderately increases cardiovascular fitness
High-Intensity Cardio (HIT) ~80–95% of max heart rate
Examples: sprints, intervals, circuits.
Primary fuel: carbohydrates (muscle glycogen).
Benefits:
- Strong stimulus for VO₂ max
- Time efficient
However, it also creates much more fatigue and should be used strategically, especially if muscle growth is the main goal.
Timing Cardio Around Resistance Training
When combining cardio and strength training, timing is key! If your main goal is muscle growth or strength, it’s generally best to:
- Perform cardio after lifting, or
- Separate cardio and lifting sessions by several hours.
High-intensity cardio before strength training will reduce performance and take away from your ability to produce force during your workout. Low-intensity cardio, such as walking, usually doesn’t create this issue.
Something to keep in mind: Just because low-intensity cardio uses a higher percentage of fat as fuel doesn’t automatically mean it leads to greater fat loss.
Fat loss ultimately depends on total energy balance over time, not which fuel source is used during a single workout.
How Much Cardio Do You Actually Need?
For most people, a moderate amount of cardio provides significant benefits without interfering with strength training.
A good starting point for many individuals is:
- 2–4 cardio sessions per week
- Mostly low to moderate intensity
- 20–40 minutes per session
From there, volume can be adjusted to support individual goals. Fat loss phases may require more cardio, while muscle-building phases often benefit from a smaller amount used mostly for health and recovery.
The Takeaway
Cardio isn’t the enemy of muscle growth. When used intelligently, it can improve health, support recovery, and even make your strength training more productive. Just like anything else, the key here is balance. Use cardio as a tool — not as punishment and not as something to avoid completely. Because the goal isn’t just to build muscle. It’s to build a body that performs well and stays healthy in the long run.
