VO2 Max. It’s not just about your mitochondria

VO2 max… why is it one of the most vital determinants of health?

We are now obsessed with VO2max. I hear it all the time in the office. But so many people don’t understand why their VO2 max is important, all the factors that go into determining it, and how to improve it. Furthermore, many people think that this is only important for athletes. Your VO2 max predicts your ability to walk stairs and perform other activities of daily living.

VO2 max, or your maximal oxygen uptake, is the highest rate at which your body can consume oxygen during intense, whole-body exercise. It’s measured in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). VO2 max reflects an individual’s aerobic physical fitness and is an essential determinant of their overall health and endurance capacity during prolonged exercise. However, much more goes into determining what your VO2 max can be than just your heart function or muscle tissue.

The significance of VO2 max lies in its comprehensive representation of the cardiovascular, respiratory, and muscular systems’ efficiency in supplying and utilizing oxygen. Essentially, it measures the body’s capacity to oxygenate blood through the lungs, transport it via the heart and blood vessels, and finally use it in muscles to produce energy through aerobic metabolism. And therein lies its significance— a solid VO2 max requires that many systems and processes in your body function optimally.

At its core, your VO2 max is super important because people in the highest quartile of VO2 max have a fivefold lower risk of dying prematurely than someone in the lowest quartile.

Key Points about VO2 Max and Its Significance:

• Benchmark for Cardiovascular Fitness: VO2 max is widely recognized as the gold standard for assessing cardiovascular fitness. Higher values are associated with better cardiovascular health, a longer lifespan/healthspan, and aerobic endurance.
• Predictor of Endurance Performance: For endurance athletes, VO2 max can predict performance, as it reflects the body’s maximum capacity to generate ATP, the energy source for muscle contractions, aerobically. However, VO2 max is not the sole predictor of achieving elite status or performance.
• Health Indicator: Higher VO2 max levels are linked to a lower risk of chronic diseases like heart disease, diabetes, cognitive decline, stroke, and obesity. It’s a valuable marker for overall health and longevity.
• Training Guide: VO2 max can help personalize exercise programs. Understanding one’s VO2 max allows optimizing training intensity to improve fitness levels effectively.

VO2 max is a critical measure of an individual’s aerobic power and overall physical conditioning. It provides valuable insights into the cardiovascular health of the general population, and it helps athletes maximize their performance goals.

Average VO2 max levels

Let’s get some basics out of the way.

Men

• 20s: 45-50 ml/kg/min
• 30s: 42-46 ml/kg/min
• 40s: 39-43 ml/kg/min
• 50s: 36-41 ml/kg/min
• 60s: 32-35 ml/kg/min
• 70s: 30-33 ml/kg/min

Women

• 20s: 35-40 ml/kg/min
• 30s: 33-37 ml/kg/min
• 40s: 31-34 ml/kg/min
• 50s: 28-32 ml/kg/min
• 60s: 26-30 ml/kg/min
• 70s: 24-28 ml/kg/min

It’s important to note that these values are averages and, as discussed later, can vary widely among individuals. People who are more physically active typically have higher VO2 max values than their less active counterparts, regardless of age. Similarly, athletes, especially endurance athletes, can have significantly higher VO2 max values than the general population.

Additionally, while VO2 max naturally declines with age, regular aerobic exercise can slow this decline. Engaging in running, cycling, swimming, or brisk walking can help maintain a higher VO2 max into older age.

What activities does a certain VO2 max enable us to do

Knowing the average VO2 max based on age is only helpful if we also know our VO2 max requirements to complete a few basic tasks. Activities such as stair climbing, jogging, and cycling require different levels of aerobic capacity depending on their intensity and duration. Here’s a general guide to the approximate VO2 max values associated with various physical activities:

Stair Climbing

• VO2 Max Estimate: Above 30-35 ml/kg/min
• Stair climbing can be an intense activity that requires significant aerobic capacity, especially for sustained periods.

Jogging One Mile

• VO2 Max Estimate: 35-40 ml/kg/min
• Jogging a mile comfortably usually requires a moderate level of aerobic fitness.

Cycling 5 Miles

• VO2 Max Estimate: 30-40 ml/kg/min
• The lower end of the range might apply to more leisurely cycling, while higher values align with a more vigorous pace.

Additional Activities for Context:

• Walking at a Moderate Pace (3 mph): VO2 max of 20-30 ml/kg/min could be sufficient for most people to perform this activity comfortably.
• Running 5k (3.1 miles): A VO2 max of 40-50 ml/kg/min is beneficial for completing a 5k run in a reasonable time without excessive fatigue.
• Swimming for 30 minutes: Swimmers might need a VO2 max of around 40-50 ml/kg/min to sustain 30 minutes of continuous swimming, depending on stroke and intensity.

Elite Athletic Performance:

• Marathon Running: Elite marathoners often have a VO2 max well above 60 ml/kg/min, with top performers reaching above 70 ml/kg/min.
• Professional Cycling: Tour de France cyclists can have VO2 max values exceeding 70 ml/kg/min, necessary for sustained high-intensity efforts over long distances.

It’s important to note that VO2 max is not the sole determinant of performance in these activities. Efficiency, technique, muscle strength, psychological factors, and specific training adaptations also play crucial roles. Furthermore, individuals can often participate in and enjoy these activities at VO2 max levels lower than those listed, especially if they pace themselves appropriately and have adapted to the activity through regular training.

Your VO2 max is far more than just a representation of your mitochondrial function. There’s so much more than that.

Let’s follow O, the oxygen molecule, on her complicated journey from the air around us to the heart of a muscle cell’s mitochondria. O’s adventure is a testament to the wonders of the human body and its quest for energy.

Chapter 1: The Great Inhale

Our story begins in the tranquil outdoors, where O whirls around with her fellow air molecules. Suddenly, she’s drawn into a grand vortex—the breath of a human being out for a morning run. O rushes through the nostrils, down the windpipe, and into a branching maze of airways, finally arriving in the expansive landscape of the lungs.

Chapter 2: Crossing into a New Realm

In the lungs, O finds herself in the bustling marketplaces of the alveoli, tiny air sacs where exchanging gases is the day’s trade. She bids farewell to a carbon dioxide molecule, a weary traveler eager to exit into the air. O then crosses the thin barrier of the alveolar wall, plunging into the crimson river of blood in a tiny red blood cell, her new vessel for the next leg of her journey.

Chapter 3: The Mighty River and the Pump

As O is swept into the heart and catapulted through the aorta into the body’s vast arterial network, she needs a reliable mode of transport to navigate the Crimson River safely and effectively. Here, O meets a special ally— H, the hemoglobin molecule.

H is a protein found within red blood cells, renowned among oxygen molecules for its ability to carry them through the bloodstream with care and precision. H introduces himself to O, offering her one of four cozy seats specially designed for oxygen molecules. Grateful for the ride, O nestles into her designated spot.

Together, O and H embark on the arterial highways within their red blood cell vessel.

The Bond

As they journey together, O learns about the special bond she forms with H—a strong yet sensitive bond to the environment. H tells her, “Our connection is vital, but it must also be flexible. As we approach your destination in the muscle tissues, the bond we share will loosen, allowing you to disembark freely and fulfill your destiny.”

O appreciates the wisdom in H’s design. The environment within the muscle cells, rich in carbon dioxide and slightly more acidic, prompts H to gently release O, ensuring that she and her oxygen comrades can move on to power the muscles at precisely the right moment.

Gratitude and Goodbyes

As their path diverges with O’s departure into the muscle cell, she thanks H for the safe passage and the invaluable role he plays in her journey. H, in return, expresses his honor in carrying her and her kind, reminding O that their partnership—however brief—is a cornerstone of life itself.

With a newfound appreciation for the intricacies of her journey, O moves forward, energized and ready for the transformative final chapter in the mitochondria, where her story will contribute to the cycle of life.

Through H, O’s story illuminates the vital role of hemoglobin in transporting oxygen, showcasing the beautifully orchestrated mechanisms within our bodies that sustain life.

Chapter 4: The Land of Muscles

As O travels through smaller roads (arterioles) and into the bustling streets of capillaries within a muscle, she marvels at the energy and activity all around her. Muscle cells contract and relax in a rhythmic dance, powered by the very oxygen she and her kind provide.

Chapter 5: The Leap of Faith

Approaching the thin capillary wall, O senses her moment has come. She takes a leap of faith, leaving behind the bloodstream and diving into the fluid surrounding the muscle cells. Guided by signals and gradients, she navigates towards a muscle cell, slipping through its membrane with ease.

Chapter 6: The Mitochondrial Quest

Inside the muscle cell, O embarks on her final quest to the mitochondria, the cell’s powerhouse. The journey is swift, as she’s eagerly awaited. The mitochondria, like ancient temples, are sites of alchemy where the breath of life is transformed into energy.

Chapter 7: The Transformation

O enters the inner sanctum of the mitochondrion, where a welcoming committee of enzymes and other molecules greets her. In a series of intricate steps, she participates in the final act of her journey—the electron transport chain. Here, O donates her electrons in a cascade of reactions that lead to the creation of ATP, the currency of energy in the body.

Epilogue: The Cycle Continues

Having fulfilled her purpose, O, now a part of a water molecule, exits the mitochondria and eventually the muscle cell itself. She may one day return to the lungs and the air, ready to begin her journey anew, a testament to the cycle of life and the intricate ballet of biology that sustains us all.

O’s adventure from a breath of air to a source of energy in the mitochondria highlights the marvels of physiology and the essential role of oxygen in powering life.

But many humans have diseases that affect our VO2 Max …

So, let’s look at her journey through a different context. Given that most people are sedentary, a majority are overweight, and only 12% are considered metabolically fit, let’s follow that oxygen molecule again and see how our lifestyle and the diseases can affect our VO2 Max.

As O embarks once more on her vital journey from the breath of air to the heart of a muscle cell’s mitochondria, she faces a series of unforeseen challenges—roadblocks caused by various diseases and conditions that threaten to derail her mission. Let’s follow O as she navigates these obstacles, highlighting the resilience and adaptability required to sustain life against the odds.

Chapter 1: The Perilous Inhale

As O prepares to enter the human body, she’s met with the first hurdle: air pollution. Particulate matter and noxious gases from the environment make her passage into the lungs more hazardous, potentially triggering inflammation and reducing gas exchange efficiency in the alveoli. Inflammation can thicken the wall of the tiny air sacs in the lung and make gas exchange much harder. Furthermore, conditions like asthma narrow the airways, turning what should be an open highway into a constricted path filled with obstacles.

Chapter 2: The Marketplaces of the Alveoli

Upon reaching deeper into the lung, O discovers the effects of chronic obstructive pulmonary disease (COPD)—the walls of the air sacs are damaged, and the airways are clogged, making it difficult for her to find her way to the bloodstream. The bustling markets of gas exchange are eerily quiet, as fewer oxygen molecules can make the crucial trade for carbon dioxide.

Chapter 3: The Crimson River’s Perils

Once in the bloodstream, O meets H, the hemoglobin, ready for their journey. However, anemia looms like a specter over their path. With not enough Hs around, O struggles to find a carrier, and the blood’s capacity to transport oxygen diminishes. In cases of iron-deficiency anemia, there’s a shortage of iron, essential for Hemmy’s creation, further impeding their journey.

Chapter 4: Detours and Blockades

As they navigate the arterial highways, atherosclerosis presents a formidable blockade. Fatty deposits narrow the roads, and O and H find themselves rerouted along more tortuous paths, delaying their arrival to the muscle cells. For those with heart disease, the mighty pump works inefficiently, struggling to propel them with the necessary force and vigor.

Chapter 5: The Muscles’ Cry for Help

Reaching the muscles, Ol senses the distress calls of cells weakened by sarcopenia, the loss of muscle mass and function. The landscape is changed, with fewer mitochondria to welcome her. With less muscle present, there is less of a need for oxygen and a decrease in our ability to use oxygen to generate power. In the realm of diabetes, elevated sugar levels in the blood create a sticky web that ensnares O, slowing her progress and complicating her delivery of life-giving energy. Furthermore, diabetes causes small blood vessel disease. This can make it hard for blood to transit the small capillary beds, and fewer capillaries are present due to sedentary behavior.

Chapter 6: The Mitochondrial Maze

Finally, within the muscle cell, O finds that the mitochondria—the temples of energy—are in disarray. Lack of consistent stimulus, insulin resistance, and other conditions like mitochondrial disorders disrupt the normal function of these powerhouses, turning what should be a smooth process of energy production into a labyrinthine puzzle. Each step of the electron transport chain is fraught with inefficiency and dysfunction.

Epilogue: The Journey’s End and Beginning

O’s journey underscores the delicate balance of health and the impact of diseases and conditions on the body’s ability to utilize oxygen. It’s a testament to the resilience of life and the importance of maintaining health—through clean air, nutrition, exercise, and medical care—to ensure that O and her fellow oxygen molecules can complete their vital mission.

O’s adventure, fraught with perils, serves as a vivid narrative for understanding how diseases and conditions can affect the body’s ability to harness oxygen, from the breath of air to the mitochondria’s energy production. It highlights the importance of preventive measures, early intervention, and lifestyle choices in safeguarding this essential journey.

Sedentary behavior, a low VO2 max, loss of muscle mass, and inability to participate in life.

Sedentary behavior, characterized by prolonged physical inactivity or low energy expenditure (e.g., sitting or lying down), has profound implications for health and functional ability, particularly as we age. Two significant consequences of a sedentary lifestyle are a decrease in VO2 max (a measure of aerobic fitness) and the development of sarcopenia (the loss of muscle mass and strength). Both of these conditions frequently accompany one another and can severely impact an individual’s ability to navigate their environment and maintain functional independence and quality of life in older age. Here’s how these factors interconnect:

Impact of Sedentary Behavior on VO2 Max

1. Decline in Aerobic Capacity: VO2 max naturally decreases with age, about 1% per year after the age of 30. Sedentary behavior accelerates this decline by reducing the efficiency of the heart, lungs, and muscles in oxygenating the body and producing energy. This reduction in aerobic capacity compromises the ability to perform even moderate-intensity activities, such as brisk walking or climbing stairs.
2. Reduced Cardiovascular Efficiency: Sedentary lifestyles lead to decreased heart muscle mass and elasticity, lower blood volume, and reduced capillary density, all of which diminish cardiovascular efficiency and further reduce VO2 max.

Sedentary Behavior and Sarcopenia

1. Muscle Atrophy: Physical inactivity is a key driver of muscle loss. Without regular use, muscle fibers diminish in size and number, particularly the type II (fast-twitch) fibers that are crucial for power and strength.
2. Metabolic Decline: Sarcopenia is associated with a decline in metabolic rate, which can lead to increased fat accumulation, insulin resistance, and a higher risk of metabolic syndrome. Metabolic disease, when present, generates significant systemic inflammation, which can potentiate the loss of muscle mass. These conditions can further limit physical activity, creating a vicious cycle of muscle loss and metabolic dysfunction.

Combined Effects on Navigating the Environment

1. Mobility and Stability: Lower VO2 max and sarcopenia together significantly impact mobility. Reduced aerobic capacity limits endurance for walking or standing, while muscle loss affects balance and stability, increasing the risk of falls and injuries.
2. Functional Independence: The ability to perform activities of daily living (ADLs), such as carrying groceries, climbing stairs, or even basic housework, is compromised. This can lead to a decreased quality of life and increased dependence on others.
3. Cognitive Function: There is growing evidence that physical activity, aerobic fitness, and muscle strength positively correlate with cognitive function. Sedentary behavior, by undermining physical health, contributes to cognitive decline.

Strategies for Prevention and Mitigation

1. Regular Aerobic Exercise: Incorporating brisk walking, cycling, swimming, or jogging into daily routines can improve VO2 max and cardiovascular health.
2. Strength Training: Engaging in resistance training exercises 2-3 times a week can combat muscle loss, improve strength, and enhance metabolic health.
3. Lifestyle Changes: Breaking up long periods of sitting with short activity breaks, opting for standing desks, and embracing a more active lifestyle can mitigate the adverse effects of sedentary behavior.
4. Nutritional Support: Adequate protein intake and essential nutrients support muscle maintenance and overall metabolic health.

Addressing the twin challenges of declining VO2 max and sarcopenia can significantly enhance individuals’ ability to navigate their environment and thrive as they age. The interplay between aerobic fitness, muscle health, and functional ability underscores the importance of an integrated approach to physical activity and lifestyle management to preserve independence and quality of life in older age.