The Role of Cardio in Gym Training: When and How Much?

21 May 2025

Cardio is one of the most debated topics in fitness. Some gym-goers swear by an hour of cardio daily, while others avoid it like the plague, fearing it will eat away their muscle gains. So, where's the balance? When should you do cardio, and how much is enough?

If you’re looking to build muscle, lose fat, or improve overall fitness, understanding the role of cardio in gym training is crucial. In this guide, we’ll break it all down in a no-nonsense, practical way.

What Is Cardio and Why Is It Important?

Cardiovascular exercise, or simply "cardio," refers to any activity that increases your heart rate and improves the efficiency of your cardiovascular system. Running, cycling, swimming, and even brisk walking count as cardio.

So, why bother with cardio? Here’s why:

- Improves Heart Health – Your heart is a muscle too! Just like biceps need dumbbells, your heart needs cardio to stay strong.
- Aids Fat Loss – Regular cardio helps burn calories, making it easier to shed excess fat.
- Boosts Endurance – If you find yourself gasping for air after climbing stairs, incorporating some cardio into your routine will help.
- Enhances Recovery – Light cardio can help flush out lactic acid and improve blood flow, speeding up muscle recovery.
- Supports Mental Health – Ever heard of a “runner’s high”? Cardio releases endorphins, which can reduce stress and improve mood.

Clearly, cardio isn’t the enemy. But how do you make it work for your goals?

When Should You Do Cardio?

The timing of cardio in relation to strength training can impact your results. Let’s look at different approaches:

1. Cardio Before Weights

Doing cardio before lifting can be beneficial in some scenarios:
- If Your Goal is Endurance: If you’re training for a marathon or a sport that requires stamina, cardio before weights makes sense.
- As a Warm-Up: A short 5–10 minute session (think jogging or cycling) can increase blood flow and loosen up muscles for a better lifting session.

However, if your primary goal is strength or muscle growth, doing intense cardio before weights can drain your energy and reduce your lifting performance.

2. Cardio After Weights

For most gym-goers, this is the best approach. Why?
- Your Lifting Performance Won’t Suffer – Strength training requires maximum effort, and hitting the weights when fresh leads to better results.
- Higher Fat Burn – Lifting depletes glycogen stores, so when you do cardio afterward, your body is more likely to burn fat for energy.
- Less Risk of Fatigue – Post-lifting cardio means you won’t be too tired to push through your heavy sets.

3. Cardio on Separate Days

This is a solid strategy if your primary goal is to either build muscle or maximize endurance. Keeping cardio and weight training on different days allows you to focus on each without compromising performance.

For instance, you could lift on Monday, Wednesday, and Friday while dedicating Tuesday and Thursday to cardio.

4. Fasted Cardio (Morning Sessions)

Some people swear by fasted cardio (doing cardio on an empty stomach). It’s believed to enhance fat burning since there’s minimal glycogen available for energy.

However, fasted cardio isn’t a magic bullet. While it may help with fat loss, it can also lead to muscle breakdown if not done carefully. If you’re opting for this approach, keep it moderate and ensure you fuel up after.

How Much Cardio Do You Really Need?

The amount of cardio you should do depends on your fitness goals. Let’s break it down:

1. If You Want to Lose Fat

- Aim for 3–5 sessions per week of 30–45 minutes.
- A mix of steady-state cardio (like jogging) and high-intensity interval training (HIIT) works best.
- Don't go overboard—excessive cardio combined with a calorie deficit can lead to muscle loss.

2. If You Want to Build Muscle

- Keep cardio to a minimum—2–3 sessions per week for 20–30 minutes.
- Stick to low-intensity cardio (like incline walking or cycling) to avoid muscle depletion.
- Prioritize weight training and ensure you’re eating enough to support muscle growth.

3. If You Want to Maintain Overall Fitness

- 3–4 cardio sessions per week for 30 minutes is great for maintaining heart health and stamina.
- You can mix it up with steady-state cardio and some interval training.

Choosing the Right Type of Cardio

Not all cardio is created equal. Let's compare the most popular types:

1. Steady-State Cardio

- A consistent, moderate-intensity pace (e.g., jogging, cycling, swimming).
- Great for endurance and fat-burning.
- Less taxing on muscles, making it ideal for recovery days.

2. High-Intensity Interval Training (HIIT)

- Short bursts of intense effort followed by rest (e.g., sprinting for 30 seconds, walking for 60 seconds).
- Burns more calories in a short time and increases metabolism after you’re done.
- Can be taxing on recovery, so avoid excessive HIIT if you lift heavy often.

3. Low-Impact Cardio

- Activities like walking, elliptical training, or swimming.
- Easy on joints and great for active recovery.
- Perfect if you're new to cardio or recovering from an injury.

Mistakes to Avoid with Cardio

To make the most of your cardio sessions, steer clear of these common mistakes:

1. Doing Too Much Cardio

More isn’t always better. Excessive cardio can lead to muscle loss, joint stress, and even hormonal imbalances. Balance is key.

2. Ignoring Strength Training

Cardio is great for heart health and fat loss, but don’t neglect weights! Strength training is essential for muscle retention, metabolism, and overall body composition.

3. Relying on Cardio Alone for Fat Loss

Fat loss boils down to a calorie deficit. If you’re not watching your diet, no amount of cardio will give you the results you want.

4. Skipping Warm-Ups and Cool-Downs

Jumping straight into high-intensity cardio can shock your body. A warm-up readies your muscles, and a cool-down prevents dizziness and stiffness.

Final Thoughts

Cardio has a place in every gym routine, but how much you need depends on your goals. If you’re focused on fat loss, incorporate 3–5 sessions per week. If muscle building is your priority, keep it limited to 2–3 short sessions.

The key is balance—too much cardio can hinder muscle growth, and too little can affect heart health. Find the right mix that suits your lifestyle and fitness objectives.

At the end of the day, cardio should complement, not sabotage, your workout routine. So lace up your sneakers, hit the treadmill, and make cardio work for you!