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If you want to get faster and go longer, you need to improve your mitochondria. These tiny powerhouses inside your muscle cells are what turn oxygen into usable energy. The more mitochondria you have and the better they work, the more energy you can produce during exercise. This means better endurance performance and the ability to maintain higher speeds for longer periods.
But not all training improves your mitochondria in the same way. Different types of training favor different adaptations. In this two-part series, we’ll break down what actually works to improve your mitochondria and how you can measure if they’re limiting your performance.
What Are the Two Types of Mitochondrial Improvements?
When we talk about improving mitochondria, we’re really talking about two separate things:
1. Mitochondrial Density and Capillary Density
This is about having more mitochondria in your muscles and more blood vessels delivering oxygen to them. Think of it like building more factories and more roads to deliver supplies.
2. Mitochondrial Function
This is about how efficiently your existing mitochondria can extract and use oxygen. Think of it like training your factory workers to be more productive.
Both are critical for endurance performance, and both require different types of training to improve.
How Do I Increase Mitochondrial and Capillary Density?
If you want to build more mitochondria and more capillaries, you need to do one thing: accumulate training volume and load. This means putting in the miles or hours at varying intensities.
When you train for extended periods (weeks, months, years), your body responds by building more mitochondria to meet the sustained energy demand. At the same time, your body grows new capillaries (small blood vessels) around your muscle fibers to deliver more oxygen-rich blood to these new mitochondria.
This adaptation doesn’t happen overnight. It requires consistent training over weeks and months. The key factors are:
- Frequency: Training most days of the week
- Duration: Longer training sessions (60+ minutes)
- Consistency: Maintaining this training load over time
We generally think of our long, steady runs or rides being most beneficial to mitochondrial density, but higher intensity training can also help to accumulate training load, which will then contribute to building more mitochondria over time. However, while easier, longer sessions might not feel as exciting as hard interval workouts, they also help to accumulate more training volume and load, while accumulating less fatigue. This lower fatigue accumulation helps us stay consistent over time and create fundamental changes in your muscles that build your aerobic foundation. Research has shown a strong relationship between training load and mitochondrial adaptations, making consistent training over time essential for endurance athletes.
How Do I Improve Mitochondrial Function?
Having lots of mitochondria and capillaries is great, but they also need to work efficiently. This is where quality, pointed, high-intensity training comes in.
Mitochondrial function refers to how much oxygen your mitochondria can extract and use to produce energy. When you do high-intensity work, you create a strong signal for your mitochondria to use oxygen from the blood and use it to generate ATP (the energy currency your muscles use).
High-intensity training improves:
- Oxygen extraction capability: Your muscles become better at pulling oxygen out of the blood
- Enzyme activity: The chemical reactions inside mitochondria speed up
To improve mitochondrial function, incorporate workouts that push you into higher intensity zones. This includes:
- High intensity interval training: Interval training close to your maximal aerobic power/speed
- Sprint interval training: Bouts of all-out efforts followed by full rest
The important thing to understand is that both types of training (easy and hard) are necessary. Volume and overall training load build the infrastructure (more mitochondria and capillaries), while intensity makes that infrastructure work better (improved oxygen extraction and utilization).
Measuring Your Mitochondrial Improvements
Now here’s where it gets really interesting. You don’t have to guess whether your training is working or which type of mitochondrial improvement you need most. You can actually use Moxy Monitor to assess whether your mitochondria are what’s holding you back.
Your body has different systems that can limit your performance:
1. Oxygen delivery: Can your heart and blood vessels deliver enough oxygen to your muscles?
2. Oxygen extraction/mitochondrial capacity: Can your muscles extract and use the oxygen that’s being delivered?
3. Breathing: Can you adequately exchange oxygen and carbon dioxide with the environment?
Using a simple assessment protocol with your Moxy Monitor, you can identify which system is limiting your performance and train accordingly. This takes the guesswork out of your training and helps you focus your efforts where they’ll make the biggest difference.
Coming up in Part 2: Learn how to perform a 3-1 limiter assessment to discover whether your mitochondria are holding you back from your best performance.
What's Your Next Step?
Whether you're stuck at a performance plateau or want to maximize your training efficiency, discovering your true limitation is the first step toward breakthrough results. Your body has been trying to tell you what it needs – now you have a way to listen.
The 3-1 limiter assessment takes ~30 minutes but could transform how you train forever. Want a more detailed guide to completing your first limiter assessment? Download the Training and Racing with Moxy eBook below!
