You look down.

Many people stare at their feet because they’re trying to see what’s going on down there. Just  put some trust in your coordination and set your eyes on the horizon straight in front of you.

Your arms cross your body.

While your right arm making its way over toward your left side with each step (or vice versa) isn’t such a bad thing on its own, it’s an indicator that your torso isn’t stable. A solid trunk brings balance and stability to the whole body—plus it protects your inner organs.

Your breathing is off.

Breathing correctly can help you run better and farther. Coupled breathing—when you breathe in a certain rhythm as you run—especially helps build running efficiency, according to one study. Researchers found this type of breathing enhanced airflow and runners felt less tired than those not paying attention to their breathing. One thing you don’t have to worry about is whether those inhales and exhales are coming from your nose or mouth.

You lift your knees too high.

Ideally, the knees should always be at less than a 45-degree angle.

You can't think of anything else but how heavy your legs feel.

If you’re thinking about how hard each step is, you’ll likely tire faster. Pump up the volume on your headphones, watch TV on the treadmill, or run with a friend. It’ll take your mind off how heavy your legs feel and keep you from giving up.

Running is your only workout.

It’s true that running is a solid workout, but it’s no excuse to skimp on strength training. Building up glute and hip muscles will help maintain your form.

You lean too far forward.

Many people follow a nine-hour workday spent sitting at a desk by popping up and going for a run. If you do that, you may end up with tight hip flexors, which makes you lean forward as you run. To fix it, incorporate hip flexor stretches into your dynamic warm-up.

Your knees touch.

It happens frequently among female runners. The root of the problem is bad glute stabilization. Once the glute muscles collapse, the thighbone rotates in and the knees collapse. Eventually, this can lead to problems with the IT band and knees.

You drink too much water.

If you overhydrate, you’ll feel bloated. Yet if you don’t drink enough, you risk dehydration, which can lead to lightheadedness or illness during your run.

You overstride.

Your foot hits the ground way ahead of your hips, almost like a gazelle. Overstriding sends a huge shock up the leg with each step—and it’s a common tendency for new runners. To fix it, try taking shorter steps and landing under your centre of mass, she says. One study showed about 85 strides per minute is golden.