Excelling at Spartan racing means excelling at both running and dynamic strength work (and at a whole lot of other things too). But while many of us train our bodies in a fairly well-rounded way, it's not unusual for fatigue to set in as the race goes on. Your endurance begins to fumble between obstacles, your body starts to break down, and your form falls apart. Correct running form is crucial to making it to that finish line, and can make or break your injury-free status. Here's everything you need to know to have correct running form.

How to Have Correct Running Form in 3 Easy Steps

Jay Dicharry is one of the premier running biomechanics experts in the country, working with top professional athletes out of his lab in Bend, Ore. The physical therapist, author of Running Rewired, tries to help runners correct their running form and get faster — something we all want. Here, Dicharry offers three things that you can do right now to start running better.

1. Fix Your Posture

Most runners (and non-runners) have “horrible posture alignment,” Dicharry says, which throws off everything. If you’re arching your lower back, it locks up the extension in your hips and hamstrings, forcing you to stretch out and overstride when you run. In turn, this reduces your running economy and increases the risk of injury.

Related: 4 Reasons Your Muscles Cramp Up (and What to Do About It)

Many people have a slouch in the upper back and shoulders. But when you think about “running tall” or standing up straight, you tend to just stick out your chest in a kind of overextended, military-style posture. In reality, this just causes a lower-back arch, which isn’t good. Instead, to have proper alignment, keep your ribs pulled down, your shoulder blades depressed and retracted, and your spine neutral.

Quick Test:

Dicharry has a quick test to see where your posture is at (and a few cues to fix it). Stand straight and feel the position of where your weight falls in the middle of your foot. Rock forward and feel it, and rock back again. Then, put one hand on your sternum and one on your ribs, and focus on dropping down your rib cage without slouching. (This helps to relax your shoulders.) Drop your hands to your sides and turn your hands so your thumbs point out, then turn them in; this will help bring your shoulders down.

Now that you feel good posture alignment, practice it.

“The more time you spend practicing bad posture, the more normal it’ll feel,” Dicharry says.

This might even mean stopping every half mile when you’re running and taking a few seconds to correct your posture.

2. Control Your Rotational Forces

Most of the work you do in the gym or while training tends to be in two directions: front and back, or left and right. But when we run, we have to contend with rotational forces, which move in more than two planes. Your torso rotates slightly as you run, and you offset it by moving your opposite arm forward with your stride.

“When we run, we have to stabilize a ton of rotational forces,” Dicharry says.

If you can’t control those rotational forces, then your form will start to break down, and you’ll have too much side-to-side movement instead of forward. (And you definitely want the majority of your momentum when running to push you forward.)

Related: 6 Ways to Start a Running Routine That Sticks

The only way to get your body prepared for rotational forces, however, is to train it with rotational forces. That means doing rotational work on your foot muscles, your hips, and your spine.

For example, when training your foot muscles (which are often overlooked), try this exercise: anchor a band to a table or another heavy object and then stand perpendicular to it, so that the band is at your side and stretches across the front of your body. Stand on one foot, holding the band in front of you with both hands, and rotate away from the anchor point and back. Turn around and repeat this while standing on the other foot. This exercise forces your foot to stabilize itself as you rotate, and requires you to push off from your big toe, which is important in running.

3. Control, Control, Control

In order to run fast, you have to apply a lot of power to the ground as quickly as possible. While general gym work and functional fitness training is good for your overall health, it doesn’t necessarily help you do that. What you need to work on is moving under control and then exploding.

Many of us have strong quads, and yet we also do gym work (like squats) that loads our quads but doesn’t help us apply power in a controlled and explosive way. If we move from being quad-dominant to being more glute-dominant, then it can help us stop overstriding and shift the muscular load.

Try this exercise: Stand holding a long dowel behind your back lengthwise, so that it touches your head, your mid-back, and your tailbone. Stand facing a box, with your toes against it. Now try to squat. Your knees won’t be able to go forward because of the box, and in order to keep your back neutral with the dowel, you’ll have to shift the effort to your glutes and hamstrings.

Related: These 3 Explosive Fitness Tests Will Expose Your Athletic Weaknesses

Deadlifts are also good, Dicharry explains, because they often force us into a neutral posture, as long as you hold neutral between reps and don’t extend out at the top.

“Make sure you control your body,” he says.

Now that you have a plan to correct running form, make sure you pace yourself. You hit peak soreness about 48 hours after a hard workout, which means that you don’t want to do a strength workout and then a sprint running workout two days apart. Instead, a common spacing is: Monday/Thursday, or Wednesday/Saturday.

“You can’t do high-intensity 100% of the time, but you can maintain good posture and body awareness 100% of the time," he says.