Cardio: The Good, the Bad, and the Balanced Truth

Cardiovascular exercise (aka “cardio”) is one of the most commonly prescribed activities in the fitness world—and one of the most misunderstood. People either fall in love with it, swearing by their morning runs, or dread it entirely, clinging to the weight rack for dear life. Like most things in health and fitness, the truth isn’t black or white. So, let’s explore the good, the bad, and the balanced approach to cardio.

The Bad: Cardio Isn’t King for Weight Loss or Body Composition

Let’s start by busting a myth: cardio is not the most effective tool for fat loss. While cardio does burn calories, it’s not efficient when compared to dietary changes or strength training. You can spend an hour on the treadmill and burn 400 calories, then unknowingly eat it back with one post-workout smoothie.

What’s worse, excessive cardio without resistance training can lead to muscle loss. This is important because the more muscle you have, the more calories you burn at rest. Translation: trading muscle for endless cardio might leave you lighter on the scale but not leaner, stronger, or metabolically healthier.

The Good: Cardio Is Phenomenal for Your Health

Now before you throw your running shoes in the trash—cardio still matters. A lot.

Cardiovascular exercise is strongly associated with reduced all-cause morbidity and mortality. Simply put: people who do cardio regularly live longer, healthier lives. It reduces your risk of heart disease, stroke, type 2 diabetes, and even some forms of cancer. It improves blood pressure, helps regulate blood sugar, enhances brain function, and boosts your mood through endorphins.

In fact, one of the strongest predictors of long-term health and mortality is VO₂ max—a direct reflection of your cardiovascular fitness.

What Is VO₂ Max and Why Does It Matter?

VO₂ max stands for maximal oxygen uptake, or the greatest amount of oxygen your body can use during intense exercise. It’s considered one of the best indicators of aerobic endurance.

A higher VO₂ max means your heart, lungs, and muscles are more efficient at delivering and using oxygen. It’s like upgrading your car’s engine—your body just runs better.

Low VO₂ max, on the other hand, is associated with a higher risk of disease and earlier death, even in people who appear healthy otherwise. This is why cardio shouldn't be dismissed—it’s a health tool, not just a fat loss tool.

How Long Does It Take to Improve Your Cardio?

Cardiovascular fitness isn’t built overnight, but the body responds relatively quickly to aerobic training. Most people can expect to see measurable improvements in cardio fitness—such as lowered resting heart rate, improved stamina, or increased VO₂ max—within 2 to 4 weeks of consistent effort.

If you’re starting from a lower baseline, the improvements can be even more noticeable in the beginning. Consistency is key.

Is Walking Considered Cardio?

Absolutely. Walking—especially at a brisk pace that elevates your heart rate—is a legitimate form of cardiovascular exercise.

While it’s on the lower end of intensity compared to jogging or cycling, walking still engages the oxidative energy system and contributes to improved heart and lung function, better mood, and lower stress. For beginners or those recovering from injury, walking is a perfect entry point into cardio training.

Cardio Uses All Three Energy Systems

What many people don’t realize is that cardio isn’t just “slow and steady.” It engages all three of the body’s energy systems depending on the intensity and duration of activity:

1. Phosphagen System (ATP-PC):

   • Fuels very short bursts of high-intensity effort (sprints, jumps, explosive movements under 10 seconds).

   • You use this when starting a sprint, jumping into a pool, or pushing hard on a hill climb.

2. Glycolytic System (Anaerobic):

   • Supports moderate-to-high intensity activity for 30 seconds to 2 minutes.

   • Think interval training, fast-paced circuits, or hard cycling sprints.

3. Oxidative System (Aerobic):

   • Dominates during longer, lower-intensity efforts like jogging, hiking, or walking.

   • It’s the primary system during steady-state cardio.

By varying the type, duration, and intensity of your cardio, you can train all three energy systems—making your body more efficient, resilient, and metabolically flexible.

What’s the “Right” Dose of Cardio?

The sweet spot depends on your goals, but general guidelines recommend:

• 150 minutes per week of moderate-intensity cardio (e.g., brisk walking, light cycling)

• OR 75 minutes per week of vigorous-intensity cardio (e.g., running, swimming)

• OR a mix of both

Ideally, aim to include a variety of cardio intensities and durations throughout the week. Combine this with strength training for a complete fitness routine.

The Bottom Line

Cardio isn’t a magic bullet for weight loss—but it is magic for your health.

Use it as a complement to strength training and healthy nutrition, not a replacement. Train all three energy systems for a more capable, durable body. And remember, the goal isn't to run yourself into the ground—it’s to build a well-rounded foundation of fitness that supports your energy, longevity, and lifestyle.