Why Muscle Is Your Health Insurance | Dr. Daniel Berzins on Building Muscle for Longevity

One of the most common questions I get is:

“If I’m going to do both cardio and strength training, can I do them on the same day? And if so—what should come first?”

The short answer: Yes, you can combine them.
The long answer? Yes—but the order matters more than most people realize.

This post will walk you through:

• Why strength training should come first

• How cardio can support fat loss and improve your metabolic health

• What “Zone 2” cardio is—and why it works

• The best time of day to exercise for consistency and hormonal balance

Why You Should Strength Train Before Doing Cardio

Your muscles rely on a molecule called ATP (adenosine triphosphate) for fuel—especially during strength training. ATP is the energy currency of your mitochondria, and it’s in highest supply at the beginning of your workout.

Starting with resistance training ensures:

• You have the energy to lift effectively

• You can perform better (heavier weights, better form, more reps)

• You lower your risk of injury due to muscle fatigue

If you burn through your ATP with 30 minutes of cardio before lifting, you’ll likely experience:

• Decreased performance

• Weaker lifts

• Increased fatigue and higher injury risk

Strength training also triggers muscle breakdown, which is necessary for muscle growth and repair. When done first, it optimizes the use of your body’s fuel reserves and sets the stage for a more effective cardio session after.

Bottom line: Lift weights first, then do cardio.

What Type of Cardio Works Best?

There’s a common misconception that you need to do hours of cardio to lose weight or improve your health. But excessive cardio—especially without resistance training—can lead to muscle loss, metabolic slowdowns, and frustration.

Instead, what you want is a strategic balance.

Resistance training builds muscle, which is critical for:

• Increasing resting metabolic rate

• Improving insulin sensitivity

• Long-term fat loss

• Stronger bones and injury prevention

Cardio, when done intentionally, enhances cardiovascular health, improves endurance, and supports fat metabolism. The key is choosing the right type of cardio and doing it in the right way.

The Power of Zone 2 Cardio

Zone 2 is a specific heart rate range where your body primarily uses fat as its energy source. This low-to-moderate-intensity zone is incredibly efficient for improving mitochondrial health and insulin sensitivity.

There’s extensive literature supporting the use of Zone 2 training, especially for people managing metabolic dysfunction or insulin resistance. Experts like Dr. Iñigo San-Millán, a leading researcher in this space, highlight its benefits even for elite athletes.

How to Estimate Your Zone 2 Heart Rate

One common method is:
180 minus your age = approximate Zone 2 heart rate.

For example, if you’re 50 years old, your target Zone 2 heart rate is around 130 beats per minute.

But since everyone’s cardiorespiratory fitness is different, that number can vary. That’s why we also use the Talk Test to personalize it.

The Talk Test

• You should be able to speak in full sentences, but it should feel labored.

• You wouldn’t want to talk much, but you could if needed.

• You definitely wouldn’t be able to sing at this pace.

If it feels too easy, you’re below Zone 2. If you’re completely breathless, you’ve gone beyond it.

Zone 2 cardio can include brisk walking, incline treadmill walking, light cycling, swimming, rowing, or using the stair stepper—done at a steady pace for a sustained period.

Aim to spend about 80% of your cardio time in Zone 2.
The other 20% can include higher intensity work, but keep it brief.

When Is the Best Time to Exercise?

While the best time to work out is the time you’ll actually stick with, there are some hormonal and practical advantages to morning workouts.

In the morning:

• Cortisol is naturally higher, which gives you more energy to train

• Your schedule is less likely to be interrupted

• It supports healthy circadian rhythms and consistent habits

Exercising in the morning can help set the tone for your day, improve mood, and make it more likely you’ll stay consistent long-term.

Final Thoughts

The ideal fitness routine for most people blends strength training and cardio—structured in a way that honors how your body builds muscle, burns fat, and adapts over time.

To summarize:

• Strength training should come first to preserve ATP and reduce injury risk.

• Follow with strategic cardio—preferably Zone 2—for optimal fat metabolism and endurance.

• Focus on consistency, and aim to work out when your body feels best and your schedule allows.

• Remember: building muscle is non-negotiable if you want to improve insulin sensitivity and metabolic health.

Whether your goal is weight loss, performance, or long-term health—this balance between resistance training and cardio is one of the most effective and sustainable ways to get there.