This article is sponsored by our partner, MitoQ.

Hard truth: Building endurance, both cardiovascular and muscular, is a long game. But while you can’t cut too many corners, there are ways to ensure you’re adding to your endurance efficiently so your training doesn’t feel like a time suck. Use this expert guidance to build endurance for OCR as expediently as possible—and sidestep injuries at the same time.

1. Start Smart

Whatever you do, don’t jump right into a 10-mile training run. “It’s always a good idea to have a solid base level of fitness before training for a specific feat,” says Greg Justice, an exercise physiologist, and owner of AYC Health & Fitness in Kansas City. Make sure you can crank out a few shorter workouts each week, then add more. 

A good rule of thumb from there: Ramp up gradually. Typical long-distance-running wisdom is to add no more than 10 percent to your mileage weekly. Studies have shown that this number is a bit arbitrary and some people can add mileage more quickly without winding up injured—but going the distance little by little is still the safest bet.

2. Go Long

You’ve got to put in the time—whether that’s long runs on the weekends or tons of reps with light weights to build muscular endurance. These sessions ensure you’re targeting not only on the right muscles but the right muscle fibers, too. “When you’re training for endurance, you’re activating slow-twitch muscle fibers that are more efficient at using oxygen,” says Justice. “This helps generate more fuel for continuous muscle contractions over a long period.” 

The more you can make your training mimic your ultimate goal, the better. “Training on a specific race course or doing obstacles that you’re going to see on race day will prepare your slow-twitch muscle fibers for the demands ahead,” says Justice.

That said, you can’t go hard every day. Alternate long or intense workouts with sessions that are shorter or easier. To keep your muscles fresh and help them bounce back faster between tough outings, supporting the mitochondria (which generate energy for your cells) with a CoQ10 supplement can help; MitoQ is one great option—it’s been shown to penetrate mitochondria hundreds of times more effectively than regular CoQ10 supplements.

3. Speed Things Up

When gearing up for a long-distance race or training your muscles to work longer, the sustained, moderate-effort session is key. But that doesn’t mean there’s no place for picking up the pace. Adding speed sessions can build endurance quickly. Just 10 speed workouts spread over 40 days led to improved running economy (read: use less oxygen), found a study in the journal Physiological Reports. 

Start by adding a tempo or threshold run weekly. This type of run, in which you hold a faster pace for a few miles, helps up your endurance because it improves lactate threshold (how long you can maintain an effort before wearing out). “The body begins to adapt to the demands you place on it and you’re able to work harder and more efficiently,” says Justice.

4. Get Stronger

You can’t only do cardio. “When you work toward muscular endurance, you’re training your muscles to perform longer before fatigue sets in,” says Justice. Target muscles you need to fire up when you’re getting fatigued. For instance, training your glutes and abs will help you stay strong in the late stages of a long race.

Working in HIIT or plyometrics can pump up your endurance too. A 20-minute HIIT workout can have similar effects on your muscles as a long, steady-state workout, according to a recent study in the American Journal of Physiology. Similarly, after just six weeks of plyo training, middle- and long-distance runners significantly improved their times in a 2.4 km run, a 2014 study in the Journal of Strength and Conditioning Research found; study authors think the improved neuromuscular and anaerobic capacity from plyo moves strengthen endurance, too.

5. Give your body a break

Recovery is especially essential following long, grueling endurance workouts. After a tough session, try contrast shower therapy, suggests Justice: Simply alternate between hot and cold water. “The theory is that constricting and dilating blood vessels helps flush out waste products in the tissues,” he explains—meaning your muscles will bounce back faster.

 Ironically, the more endurance you gain, the more crucial recovery becomes. “The closer you get to your goal, the more you need to focus on it,” says Gunnar Peterson, celebrity trainer and director of strength and endurance for the NBA’s Los Angeles Lakers. “To continue to see improvement, you have to dial in nutrition and focus on recovery.” One way he primes his muscles for recovery is with MitoQ. “It helps muscles on a cellular level and make sure that foundation is laid for your next workout.” 

6. Don’t Be Afraid to Dial It Back

We’re all for “go big or go home.” But easy there, Tiger. “Overtraining is a common mistake with endurance athletes,” says Justice. Signs you might need to take a step back: extreme fatigue, chronic muscle aches or joint pain, frequent sickness, insomnia, or decreased performance. If you notice any of these symptoms, says Justice, “It’s time to reconsider your training regimen.” Otherwise, you risk getting sidelined with an injury.

It’s true: Sometimes less is more.