The Engine Under the Hood
From Director of Health Alex Maples
When most people think of cardio, they’re thinking about burning calories. And while it does burn calories, that’s just one tiny part of the picture. In fact, if your primary goal is weight or fat loss, cardio may not even be the most effective tool (something we’ll dig into more when talking about body composition).
But here’s the truth: Cardiorespiratory fitness offers a huge return on investment that has nothing to do with calorie burn. From heart health to brain function to how long – and how well – you live, its impact is both broad and profound. It’s not just about burning energy. It’s about building capacity.
CRF and Your Baseline Operating System
Cardiorespiratory Fitness (CRF) is your body's ability to deliver oxygen to muscles during sustained physical activity. It’s a measure of how well your heart, lungs, blood vessels, and muscles all work together as a team. Good cardiorespiratory fitness doesn’t just help you during a workout – it upgrades your default state. Here’s what that means:
Lower Resting Heart Rate & Blood Pressure
With higher CRF, your heart becomes more efficient. It pumps more blood per beat, so it doesn't need to work as hard at rest. This translates to:
Lower resting heart rate (often 50–60 bpm in fit individuals)
Lower blood pressure
Better blood flow to the brain and organs
This improved efficiency makes everyday tasks – climbing stairs, walking, standing for long periods – feel easier. You’re simply operating with a better engine.
More Resilient Nervous System
Higher CRF enhances autonomic balance, improving parasympathetic tone (your “rest and recover” system). That means:
You handle stress better
You recover faster from both workouts and life events
Your heart rate variability (HRV) tends to improve (a marker of adaptability and nervous system health)
Protective Effects of High CRF
Lifespan extension: A 2018 JAMA study found that higher CRF is associated with significantly lower risk of all-cause mortality, with no upper limit of benefit.
Reduced cardiovascular risk: Lower risk of heart disease, stroke, hypertension.
Improved metabolic health: CRF improves insulin sensitivity and blood sugar regulation.
Brain benefits: Better mood, memory, and protection against cognitive decline.
Protective effect across BMI categories: The “fit but fat” phenomenon – CRF can partially offset risks associated with higher body fat.
Consequences of Low CRF
Low CRF doesn’t just make life harder – it makes it shorter.
Increased mortality risk: Low CRF is as deadly as smoking, diabetes, or hypertension.
Fatigue and poor recovery: Less energy for daily life, workouts, or stress resilience.
Higher disease burden: Increased risk of cardiovascular, metabolic, and neurodegenerative diseases.
Faster aging curve: Mitochondrial decline, reduced capacity to handle physical and psychological stress.
How to Improve CRF
First and foremost, Get Moving! While there is more nuance to it than that, movement is the foundation of good CRF. The best part is it doesn’t matter how you do it – you can walk, hike, bike, run, row, paddle, swim, dance, jump rope, or play sports. The list goes on and on. The options for expanding CRF are vast and if you explore enough, you will likely find a few that you enjoy. Movement and expressing what our bodies are capable of can be some of the greatest joys in life, not only can it be fun, it can be really good for us too!
