Your body’s biggest limit might just be your anaerobic threshold.

“The anaerobic threshold is the exercise intensity at which the demands of exercise can no longer be met by the aerobic system with oxygen,” explains SGX L2 coach Chris Anne Beardslee-Myers. “When the threshold is exceeded, fatigue will quickly start to set in.” Your breathing gets faster, your heart pounds harder, and your muscles start burning. Your body will give out; it’s a physiological inevitability. 

The solution: move your threshold. Performing sprints—pushing past your cardio threshold for short bouts, again and again—you force your body’s aerobic system to adapt and your threshold to increase. As a result, you’ll be able to work harder, longer both in training and on the Spartan course, she says. 

More WODs This Week: 4 Timed Running Intervals to Better Performance Overall

The Top HIIT Sprint Workout to Boost Your Cardio Threshold

Warm Up

This sprint workout, courtesy of Chris Anne, will help you make it happen. To warm up, spend at least 10 minutes performing activation exercises such as bodyweight squats, leg swings, arm circles, side lunges, and ankle circles. Then find a shallow hill that’s about 100 meters long and get ready to push your limits.

Related: The No-Equipment-Needed Workout to Build Muscle and Burn Fat

Hill Sprints

Starting at the bottom of the incline, sprint to the top with max effort. Once you reach the top, immediately perform 10 burpees with excellent form. Take 30 seconds to jog or walk down the hill, allowing you to catch your breath. (If you need more, take up to 60, but try to cap it there.) At the end of 30 seconds, sprint back up the hill and repeat for a total of 10 rounds. That’s 100 burpees!

Related: Sandbag Burpees: 10 Minutes to Build Muscle and Burn Fat On the Go

Rest for 3 minutes.

Next, perform the following exercises, holding each for 2 to 3 seconds. 

Slow Mt. Climbers/Lizards

Get into a plank on your hands. Slowly bring one knee toward the chest without rounding the back or losing the plank position. Return your foot to the floor and repeat on the other side. Fom here, bring your foot up next to your hand, hold for 3 to 5 breaths, and then open the knee out to the side away from your body. Hold this position for 3 to 5 breaths, then repeat on the other side, and return to a plank position. That’s one rep. Do 10.

Related: The 15-Minute Plyobox Bodyweight Workout to Up-Level Your Lifting Game

Up Dog/Down Dog

Standing up, place your hands on the floor in front of you to get into down dog. With your heels on the ground, straighten your legs and push your hips up toward the ceiling. Hold for 3 to 5 breaths, then shift your body weight forward. Press your hips down, your chest up, and your shoulders back and down. Hold for 3 to 5 reps, then press through your hands to return to down dog. That’s one rep, do 10.

Related: 4 Essential Bodyweight Exercises You've Probably Never Tried

Slow Negative Push-up/Push-back 

Get in a push-up position and slowly lower your chest toward the floor over a count of 3 to 5 seconds. At the bottom of the push-up, press through your chest and shoulders to press your hips back between your thighs. Hold for 3 to 5 seconds and then return to a push-up position. That’s one rep. Do 5.

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