We all want to feel stronger, be faster, and go longer. To get there, we need endurance—and as you might expect, building endurance is a slow and steady process, not a race.
Endurance training is all about increasing a little something called ‘mitochondrial density.’ Mitochondria, organelles that power your cells, are responsible for converting energy and supporting oxygen exchange between tissues (which our muscles need to work harder). “When the number of mitochondria in your cells goes up, your muscles can go harder for longer, regardless of the endurance event,” explains Derek Mikulski, CSCS, founder of ActivMotion Bar.
So, you wanna increase your mitochondria? Here’s exactly how to do it.
1. Train at sub-maximal intensity
“To increase mitochondrial density, science shows that training at sub-maximal intensities over prolonged periods of time is best,” says Mikulski. That means working at roughly 60-70 percent (but never exceeding 85 percent) of your max heart rate during training.
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2. Don’t forget to strength train
Whether you’re running, biking, or swimming, keeping your muscles strong for long activities will lower your risk of injury and provide you with a more stable, athletic posture. “Try to sprinkle in two days of strength training throughout each week, focusing on the core, legs, and upper body each strength day,” says Mikulski.
3. Mix it up
We know, you love going to that Pilates or dance class three days a week. But switching up your routine is key for building endurance. In order for your body to change, it can’t get too comfortable with your fitness routine.
“Make sure your workout is constantly changing so that you can build up stamina, opposed to getting used to a cycle,” says Dr. David Greuner, cardiovascular surgeon of NYC Surgical Associates. “This way, your muscles are constantly learning new ways to move and change.”
4. Go little by little
Running isn’t everyone’s cup of tea, but have you given it a proper shot? It’s essential to start of small, running a few minutes with a few walk breaks in between each sprint. “Each day add in an extra minute of running and one less minute of walking,” says Dr. Greuner. “Soon you’ll be able to run a full 30 minutes, or longer. This kind of slow increase in time can be applied to almost all cardio and even all working out.”
5. Aim For Time Over intensity
Remember what we said about sub-maximal intensity? Endurance is built by consistent duration rather than short and intense efforts. “The longer you go for by necessity, the less intense the effort will have to be,” says Albert Matheny, MS, RD, CSCS, co-founder of SoHo Strength Lab and advisor to Promix Nutrition.
“You can’t sprint at top speed for an hour but you can jog for an hour. The time builds the physical endurance,” says Matheny. “It is built by movement efficiency and physiological changes. Both types of change take time and repetition,” says Matheny.
6. Track Your Progress
There are plenty of ways to do this: apps, accountability partners, calendars, or even an old-fashioned notebook. “This way, you’ll always remember where you’re at, and can actually see your progress—which will keep your motivational endurance up, too,” says Mansour.