What Is the BOLT Score Test?
The BOLT Score stands for Body Oxygen Level Test. It was developed by Patrick McKeown, author of The Oxygen Advantage. The test measures your body’s tolerance to carbon dioxide (CO2), which reflects how efficiently you use oxygen. The idea is simple: a higher BOLT score usually means better respiratory function, endurance, and overall wellness.
Here’s how you do it:
- Sit down calmly and breathe normally through your nose.
- Take a small, normal breath in and out through your nose.
- After the exhale, pinch your nose and start the timer.
- Hold your breath until you feel the first definite urge to breathe.
Let go of your nose and resume breathing normally. That number of seconds? That’s your BOLT score.
Important: Don’t hold until you’re gasping for air. It’s not a max breath-hold test. It’s about sensitivity.
The BOLT Score Test for runners and everyday people alike is an easy, at-home test of your breathing efficiency. It doesn’t require exertion, but it offers powerful insight into your body’s current state. It’s especially useful if you’re curious about your breathing capacity or dealing with issues like shortness of breath, asthma, or anxiety.
Even if you’re just starting a new fitness journey, this test is a perfect benchmark to track improvements in CO2 tolerance over time.
Why Does Your BOLT Score Matter?
Here’s the thing about your breathing: the better your body tolerates carbon dioxide, the better you can deliver oxygen to your muscles and brain.
When I first did the BOLT test, my score was 14 seconds. I was shocked. I run four times a week. I thought I was fit. But that low number told me my breathing was shallow and inefficient. After just two weeks of nasal breathing and light breath holds, my score went up to 22. I could feel the difference on my runs.
Your BOLT Score correlates with:
- Nasal breathing efficiency
- Oxygen delivery to tissues
- Cardiovascular endurance
- Recovery speed
- Anxiety and stress levels
Think of it this way: if your breath is unsteady at rest, how can you expect it to be smooth when you’re running hills or swimming laps?
What is a good BOLT Score depends on your goals, but generally, anything above 25 seconds is considered solid for athletes. Some endurance athletes aim for 40+ seconds, indicating strong breath control and stress resilience.
If your BOLT score is low, don’t panic. It doesn’t mean you’re unhealthy; it means your breathing habits might need some attention. Over time, your CO2 tolerance can improve through specific breathing exercises to increase your BOLT score.
How Does the BOLT Score Work Scientifically?
Let’s break it down. Your breathing is governed by CO2, not oxygen. When CO2 builds up, your brain tells your body to breathe. The BOLT score measures how long you can delay that response, indicating your CO2 tolerance.
Higher tolerance = less frequent, deeper breaths = more oxygen delivery.
It’s like tuning your body’s fuel efficiency. Instead of revving the engine with every breath, you learn to run on steady, controlled power. That’s why free divers, elite runners, and yogis often have high BOLT scores.
Here’s an analogy: Think of CO2 tolerance like your body’s braking system. A low BOLT score means you’re slamming on the brakes too early. A high score means you’re cruising comfortably.
What’s fascinating is how this test relates to oxygen advantage breathing techniques. These methods aim to reduce over-breathing and promote more efficient gas exchange in the lungs. When you breathe less but better, you unlock natural endurance without overexertion.
Does the BOLT Score measure fitness? Not directly like a treadmill test would, but it gives insights into your breathing capacity, respiratory control, and how well your body utilizes oxygen. Especially at rest. And for endurance sports, those factors can be game-changers.
For a deeper dive into how CO₂ tolerance enhances both athletic performance and mental resilience, see this article on CO₂ tolerance and its impact on athletic and mental performance.
What Is a Good Score?
| BOLT Score (Seconds) | Interpretation |
|---|---|
| < 10 | Very low. Likely over-breathing and poor CO₂ tolerance. Breathing retraining is recommended. |
| 10–20 | Below average. You may experience breathlessness during moderate activity. Improvement is very possible. |
| 20–30 | Good baseline. Indicates decent breathing efficiency and aerobic fitness. Great for recreational athletes. |
| 30–40 | High CO₂ tolerance. Suggests strong breath control, calm under pressure, and solid endurance capacity. |
| 40+ | Excellent. Common among elite endurance athletes, free divers, and those with highly efficient breathing patterns. |
So, how to improve your BOLT Score breathing? Start by recognizing where you fall in this chart and what it says about your respiratory health. If you’re in the lower brackets, that doesn’t mean you’re unfit. It just highlights that your breathing might be a limiting factor in performance.
Athletes aiming for a VO2 max increase often forget that improving carbon dioxide tolerance is a foundational step. Better breath control reduces the rate of perceived effort. It can even help manage exercise-induced asthma symptoms.
For a breakdown of oxygen capacity benchmarks, explore our VO2 max chart for men to see how aerobic metrics compare.
Many beginner runners ask, “Is my BOLT Score too low?” If it’s under 20, that might explain why you feel winded quickly. But the good news? This is something you can actively train and change.
How Can You Improve Your BOLT Score?
Improving your BOLT score isn’t about doing more cardio. It’s about retraining how you breathe. Here are a few proven methods:
- Nasal breathing throughout the day and during workouts
- Breath holds (especially after exhaling lightly)
- Reduced breathing exercises to reset your respiratory center
Start small. Try breathing through your nose during a brisk walk. Or do light breath holds while sitting at your desk. After a week or two, test your score again. Most people see progress in days.
A tip from my coaching journal: One client went from 11 seconds to 27 in under a month, simply by walking daily with their mouth closed. The change in their resting heart rate and energy levels was dramatic.
Want to know how to increase CO2 tolerance even more? Integrate low-intensity breath holds during warmups. After a gentle exhale, hold for 5 to 15 seconds, then breathe calmly. Repeat 3 to 5 times. This resets your CO2 sensors and builds tolerance safely.
Apps and wearables are catching up, but the BOLT Score Test still beats most digital tools. It’s body-led, not device-led. That simplicity keeps it honest.
Think of your lungs like a balloon. Over time, gentle stretches help it expand and recoil more efficiently. Breath training works the same way. You stretch and strengthen your respiratory control with intention.
How to Increase Your BOLT Score
If your BOLT score is lower than you’d like, don’t worry. It’s absolutely trainable. Many people improve their score significantly with just a few minutes of targeted practice each day. The key is consistency, not intensity.
Here are some science-backed strategies to help you raise your BOLT score:
1. Nasal Breathing (All Day, Every Day) Your nose is your breathing superpower. Breathe through your nose while working, walking, and especially when exercising. It slows your breath, reduces over-breathing, and supports nitric oxide production for better oxygen delivery.
2. Light Breath Holds After Exhalation A few times a day, exhale gently, then pinch your nose and hold your breath for 5–15 seconds. Resume nasal breathing afterward. This trains your CO2 tolerance safely. Never push to extreme discomfort.
3. Reduced Breathing Exercises Try breathing slightly less than normal until you feel a light air hunger. Hold that gentle discomfort for 1–2 minutes, then return to regular breathing. This resets your brain’s sensitivity to carbon dioxide.
4. Improve Posture and Core Stability Slouched posture impairs diaphragm movement. Practice standing and sitting tall with engaged core muscles. Try breathing into your lower ribs and belly instead of shallow chest breaths.
Posture and core training pair powerfully with mindful cooldowns. Check out this cooling down after running guide that includes breath-focused recovery techniques.
5. Mouth Taping During Sleep Using special mouth tape can encourage nasal breathing overnight. This has helped many people improve snoring, sleep quality, and their morning BOLT score.
Over time, these habits help reprogram your brain’s automatic breathing pattern. It takes patience, but the rewards are huge: improved endurance, reduced anxiety, better sleep, and faster recovery.
One of the most powerful things about the BOLT score is that it gives you real-time feedback. You can test weekly and see improvement, which makes the process feel rewarding and motivating. Ask yourself: if your breath improved 10% each week, how would your workouts and focus change?
So if you’ve been wondering how to improve your BOLT score breathing, the answer lies in retraining your baseline habits. Breathe light. Breathe slow. Breathe through your nose.
To strengthen your base breath control, explore our detailed Zone 2 running pace guide and learn how easy aerobic efforts can boost CO₂ tolerance.
Is the BOLT Score a Fitness Test or a Health Tool?
It’s both. That’s the beauty of it.
You might use the BOLT Score Test to measure endurance readiness, but it also helps with:
- Asthma and allergies
- Sleep quality (especially snoring or sleep apnea)
- Anxiety regulation
- Post-COVID breath recovery
The test is safe, free, and can be done anywhere. It’s one of the most underused wellness metrics out there.
Breath training for better performance is gaining traction in elite sports, but everyday people benefit too. I’ve seen office workers, yoga beginners, and even retired athletes use it to reconnect with their bodies and feel more grounded.
Have you ever noticed your breathing during a stressful meeting or before a big race? The test gives you a baseline. You can check in with yourself anytime, not just during workouts.
So, is it a health tool or a performance gauge? It’s your daily check-in. Your breath, your signal.
What If Your Score Is Really Low?
Don’t worry. A low score isn’t a failure, it’s just feedback.
Your body might be stuck in a pattern of over-breathing. Maybe from stress, poor posture, or years of shallow breathing. That can change.
Start slow. Focus on quiet, light, and nasal breathing. You don’t need to overhaul your fitness routine. You just need to breathe a little better every day.
Let’s be honest, it’s not glamorous. But the results? Better runs. Better sleep. Better calm.
Test your breathing capacity at home regularly. If you’re training, record your BOLT score alongside your pace or heart rate. It’s a hidden metric with visible benefits.
Use it as a recovery marker after illness. Or as a breath-focused meditation tool. One of my clients recovering from a chest infection used the BOLT score to rebuild confidence in her breathing, step by step.
Remember, change happens in small, consistent steps. And this one only takes a few seconds.
Next Steps: Make Breath Training a Daily Habit
Now that you understand your BOLT Score and what it means, it’s time to put that knowledge into action.
Start your day with a breath awareness check-in. Sit for two minutes. Breathe in and out through your nose. Keep it light and quiet. This builds awareness and sets the tone for your respiratory system.
You can also use nasal breathing for endurance athletes during warmups, cooldowns, or even sleep. Tape your mouth at night (using specialized mouth tape) to encourage nasal breathing overnight—a proven way to raise your BOLT score and improve sleep quality.
Track your progress weekly. Pair your BOLT test with heart rate data, sleep scores, or even journaling how you feel. Over time, you’ll notice trends that show real, meaningful improvement.
Your breath is always with you. Use it. Train it. Trust it.
And if you’re looking to deepen your practice, consider learning about the Oxygen Advantage breathing technique, which combines science-backed breath holds and nasal training methods to optimize performance.
Because here’s the truth: no matter your sport, your health condition, or your age, better breathing changes everything.
