What is Fitness?

Fitness isn't what most people think it is. We explain the real world of fitness, how you measure and track it, and what it means for you living a healthier life.

What is Fitness?
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"I want to be fit." I hear that so often. Yet, I'm not sure what they mean, and, quite often, they don't know what they mean either.

Do they want to podium for a 10k, complete their first marathon, bench 225 pounds, or enable themselves to be able and cognitively intact when they're 90? Or do they just want to increase their cardiovascular fitness as measured by something linked to health and lifespan, like VO2 max?

People talk a lot about "fitness", as do we here at Simplavida. Depending on the context, it can mean one or more of many things, like metabolic fitness, strength, power, aerobics, or balance. The concept of being fit will mean different things to different people, depending on your goals, age, history, and so on. What does the concept of fitness mean to you?

As we say in our Mission Statement. "... no bro science and no magic, just a focus on simplicity and consistency across all domains of human health and wellness, from the physical, to the mental, to the social and financial. They are all linked, but that doesn't mean it has to be complicated. So, Simplavida."

Exercise is by far the best mechanism we have available to us to achieve a longer, healthier, and more capable life. It is free medicine, and nothing else even comes close. But, your concept of fitness may affect your ability to achieve your goals.

When we talk about fitness, we are more often than not referring to cardiorespiratory fitness (CRF). Your VO2 max, or the amount of oxygen you can deliver and use in your peripheral tissues during exercise, is a strong predictor of mortality. As a growing body of work shows, independent of everything else, simply having a higher VO2 max is associated with a longer and healthier life.

Time to clarify some terms. People tend to use various words interchangeably when it comes to aerobic fitness, as well as tossing in fitness jargon. They will talk about "cardio", "cardiovascular fitness", and "cardiorespiratory fitness", as well as "VO2 max". It's worth knowing the differences.

Cardio: A generic term used mostly by non-medical sorts to describe any sort of aerobic exercise. But at its root is the Greek word "kardia", which has to do with the heart. So, cardio, formally is anything that affects the action and health of the heart. Exercise does that, as do many other others, including sex.

Vascular: This also comes from the Greek, specifically the word "vasculum," meaning a small vessel. In medicine "vascular" refers to the complex system of blood vessels within the body, including arteries, veins, and capillaries. Collectively they transport blood throughout the body.

Cardiovascular: Combining the previous two terms, this refers to the integrated action of the heart and blood vessels: Cardio + vascular. So cardiovascular fitness is then the capacity of that system to do what it evolved to do, both in steady state and when responding to sudden needs.

Cardiorespiratory: We are now combining cardio (the heart) with respiration (the act of breathing), so this is an even broader perspective on the various systems working together that keep us alive. So cardiorespiratory fitness (CRF) includes cardiovascular fitness and thus refers to the health of the heart, lungs, and circulatory system in delivering oxygen to the body's tissues during sustained physical activity. CRF reflects the integrated ability to transport oxygen from the atmosphere to the mitochondria to perform physical work. It quantifies the functional capacity of an individual and is dependent on a linked chain of complex processes that include lung function and diffusion of oxygen into the blood vessels. It also includes right (venous) and left (arterial) side cardiac function, the ability of the blood vessels to efficiently transport blood from the heart, and the ability of our muscle cells to receive and use (mitochondria) the oxygen and nutrients delivered by the blood. CRF is, therefore, directly related to the integrated function of numerous systems, and it is thus considered a reflection of total body health. This complex integrated physiology is reflected in our VO2 max.

VO2 max: If you think of your body as a car, then VO2 max is a measure of its engine efficiency crossed with the fuel system capacity. In this metaphor, just as a car can go faster and further if it burns fuel more efficiently, the human body functions better if it can do more with the oxygen (fuel) it consumes. That is the essence of VO2 max. And it also tells you why it is measured in mL/kg/min: how much oxygen you process per kilogram of body weight per minute. That's your fuel efficiency.

But fitness doesn't stop at the cardiorespiratory system. Strength and power are important, and become even more so with aging, given natural declines in both, as well as in balance, which leads to falls and frailty cascades. In upcoming posts, we will write more about balance and other often ignored abilities we need to maintain to age well.

Compared to those in the top 5% of VO2 max, those in the lower 25% are 5 times more likely to die in 10 years.

We are working on apps and services to assist you in this pursuit of higher levels of cardiorespiratory fitness. But while technology is great, however, it gets you nowhere without goals. And our goal should start with living a well-intentioned and capable life.

In the next section, for premium subscribers, we go into this in much more detail. What measures are the most important ones for overall fitness? Which ones are manipulable? What do they affect? We will dive deeper into the concept of fitness, the measures of fitness, what drives them, and how our goals can help us achieve fitness.

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