VO₂max: Why It’s Not Just About Cardio

When most people hear VO₂max, they immediately think of endurance athletes runners pounding out miles or cyclists pushing through long intervals. Traditionally, VO₂max (the maximum amount of oxygen your body can use during intense exercise) has been seen as a marker of aerobic fitness, determined almost entirely by cardiovascular training. This has become a HOT topic now with a recent 60 minutes interview with Dr. Peter Attia, where he made some big claims about VO2max, especially around longevity.

 

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But here’s the truth: VO₂max isn’t just about how much cardio you do. Resistance training, when structured intelligently, can meaningfully improve VO₂max and overall metabolic health. To understand why, we need to unpack what VO₂max really measures, what influences it, and how strength-based approaches can enhance it in ways that pure endurance training can’t. We are going to see that VO2max is much more than just the aerobic training that most people associate with this concept.

What VO₂max Really Measures

VO₂max represents the peak rate at which your body can transport and utilize oxygen during exercise. It’s a product of two major systems working together:

1. Central factors – how efficiently your heart, lungs, and blood vessels deliver oxygen to your muscles.

2. Peripheral factors – how effectively your muscles extract and use that oxygen to produce energy.

Think of it this way: your heart and lungs deliver the “fuel,” but your muscles are the “engine.” Both sides matter equally. Traditional aerobic training, like running or cycling, mainly improves the central components by strengthening the heart and increasing blood volume. But muscles also adapt profoundly to how they use oxygen, and that’s where resistance training can make a real difference.

The Role of Muscle in VO₂max

Skeletal muscle isn’t just for movement — it’s a metabolic powerhouse. Muscles determine how much oxygen you can use by influencing:

• Capillary density: more tiny blood vessels mean better oxygen delivery.

• Mitochondrial content: mitochondria are your cells’ energy factories, converting oxygen into usable fuel.

• Enzymatic efficiency: enzymes involved in oxidative metabolism improve with training that challenges endurance and strength together.

• Fiber type recruitment: strength training can enhance Type IIa “hybrid” fibers, which bridge the gap between fast, powerful contractions and sustained aerobic work.

Resistance training especially when performed with minimal rest, higher volume, and multi-joint movements taps into these exact adaptations. Studies have shown that circuit-style resistance training, high-intensity functional training (HIFT), and loaded movement-based exercise (like Ultimate Sandbag or kettlebell complexes) can improve VO₂max almost as effectively as traditional endurance training.

Research Backs It Up

In a 2019 meta-analysis published in the Journal of Sports Medicine, researchers found that resistance training improved VO₂max in both untrained and trained populations. Interestingly, when the workouts included compound lifts, shorter rest intervals, and moderate to high intensity (around 60–80% of 1RM), the aerobic improvements were comparable to steady-state cardio programs.

Other studies echo this. For example, another study (PMID: 33924785 ) “With regard to cardiorespiratory fitness, circuit training had a favorable effect on VO2max , maximum aerobic speed or power , and aerobic performance after training. Concerning strength outcome, the circuit training increased the strength of the upper and lower extremities.”

And more recently, sandbag resistance protocols and kettlebell circuits have demonstrated acute increases in oxygen consumption equivalent to 70–80% of VO₂max values. This shows that functional resistance work can challenge the cardiorespiratory system just as much as cardio when intensity and total work are properly managed.

 

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How Resistance Training Enhances VO₂max

Here’s how resistance training achieves cardiovascular benefits that go beyond “lifting heavy”:

• Metabolic demand: Large muscle groups working simultaneously (like in squats, presses, or loaded carries) elevate heart rate and oxygen consumption substantially.

• Peripheral adaptations: Muscles increase capillarization and mitochondrial density, improving local oxygen extraction.

• Improved cardiac output: Repeated bouts of near-maximal effort (like circuit intervals) strengthen the heart’s stroke volume.

• Movement efficiency: Strength training enhances coordination, reducing the energy cost of movement — effectively raising how far or long you can go before fatigue.

• Hormonal and recovery balance: Strength training supports lean muscle retention, insulin sensitivity, and recovery capacity, all of which indirectly sustain aerobic performance.

When combined with aerobic work, resistance training doesn’t just complement it, it amplifies it. Hybrid approaches, such as metabolic resistance training or high-intensity interval lifting, target both the central and peripheral systems, creating a more complete fitness foundation.

The Takeaway: VO₂max is Multifaceted

Your VO₂max isn’t determined by how long you can stay on a treadmill it’s shaped by how well your entire body works together to deliver and use oxygen. Strength training, when structured with purpose and intensity, can dramatically elevate those capacities.

Functional resistance exercises can push both your muscles and cardiovascular system to adapt. You’re training strength, coordination, and endurance simultaneously, which translates to real-world performance and long-term health.

So the next time someone says you need endless miles of cardio to improve your aerobic fitness, remember: VO₂max isn’t just built on the road it’s forged under the bar, through intelligent, full-body movement. This makes longevity, building muscle, and improving VO2max all at the same time with better training.

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