Squats are to leg day as sheet masks are to #selfcaresunday: essential. As many face mask options as there are in the world, there might be even more variations of the classic booty-building move. There are goblet squats, sumo squats, barbell back squats, jump squats, and loads more. Trust us, squats aren't going anywhere soon—but there’s one variation your routine may be missing.

Enter: The Bulgarian split squat—also referred to as the rear foot elevated split squat or just simply a split squat. “Bulgarian split squats are one of the best movements for developing glute, quad, hamstring, and core strength because it’s a unilateral exercise—meaning that it works and strengthens one leg at a time,” certified personal trainer Quianna Camper, a trainer with RSP Nutrition, tells Health.

Why is unilateral leg training such a big deal? According to physical therapist and certified strength and conditioning specialist Grayson Wickham, founder of Movement Vault, it comes down to compensation. “Most people are not perfectly symmetrical. So their right leg or glute might be stronger than the left, which means when you do a normal squat, the stronger side will compensate," he says. "Single-leg exercises like the split squat can help fix those muscle imbalances by developing that lower-body and core strength symmetrically.” Some research even suggests that unilateral exercises are more effective for building strength than bilateral movements like the standard squat. (Talk about upgrading your leg day).

RELATED: 6 Ways to Upgrade a Basic Squat

Because you need to activate your core during Bulgarian split squats in order to keep your chest upright, Camper says, “they also help you build core strength, and the benefit of that is that it improves your overall balance and stability.” Translation: Add Bulgarian split squats to your routine and you’ll sculpt a peach, strengthen your quads and core, and decrease risk of falling (and therefore injury) as you age.

Ready to feel the booty burn? Below, Wickham and Camper walk you through how to do a Bulgarian split squat, plus a few variations of the super-effective single-leg move.

How to do a Bulgarian split squat

Start standing with your feet hip-width apart, facing away from a box, bench, or chair that is no higher than your knees. Extend your left leg back and put the top of your foot (aka laces down) on the box. If this is uncomfortable on your left ankle, you may want to pad your left ankle with a yoga mat or towel. Then, readjust your right leg so that you're standing 12–24 inches in front of the box, hips squared forward. This is your starting position.

When you’re ready to begin, tuck your tailbone, engage your core, and draw your shoulders back. Keeping your chest up, lower your hips into a front lunge position by bending your right knee and dropping your left knee straight to the ground.

Continue lowering until your right thigh is parallel to the ground—or as low as you can go without feeling something you'd describe as "strain," Wickham says. (If you lack hip mobility, you may start to feel an intense stretch before you get very low, so stop descending and return to start.)

Once at the bottom, drive up through your right heel and straighten your right knee to return to the starting position. That’s one rep. Repeat for 8 to 10 reps before switching legs.

RELATED: 8 Ways to Amp Up Your Bodyweight Workout

To make it easier: Start with a basic split squat

Elevating your rear foot requires a ton of balance and stability, which means it necessitates a prerequisite level of core, glute, and quad strength. That’s why Camper recommends working up to it by first mastering the basic split squat.

“Start by standing in a staggered-stance position, with your feet hip-width apart and right foot about two feet in front of the other. Place your hands on your waist and square your hips forward. Then lower your body until your knee touches the floor, and come up into start position contracting your legs and glutes,” explains Camper. That’s one rep. She suggests doing 12 to 15 reps before switching legs.

To make it harder: Add weights to your Bulgarian split squat

If you have strength-training experience, Camper says you can try adding weight to kick things up a notch. “Just make sure you can do 3 sets of 15 reps on each leg [with your body weight] before playing around with weights," she says.

According to Wickham, there are lots of ways to add weight to a Bulgarian split squat. You could hold a dumbbell in each hand, one weight in front of your chest, or even use a barbell on your back, he says. The added resistance of any of these variations will help you target the glutes.

Whichever weight you grab, be sure to pay extra attention to keeping your shoulders back and down and your chest up, Wickham says. Dumbbells and kettlebells make for easier weighted options; when you're ready to try a barbell split squat, he suggests starting with an empty barbell first and slowly adding weight from there. (Because of the box or bench behind you, bailing with the barbell can be dangerous. “Choose a weight you know you can hit,” advises Wickham.)

RELATED: 4 Exercises Trainers Never Do (And What to Do Instead)

How to add Bulgarian split squats to your routine

Try to incorporate split squats every other time you do leg day, says Camper. “Either do them in place of your back or front squats, or do them first,” she says. While form is always important when you squat, doing split squats with tired muscles can lead to injury if you’re not extra careful, she adds.

Both Camper and Wickham recommend pairing split squats with deadlifts, glute bridges, wall balls, or dumbbell box step-overs—or core exercises like planks, bird dog, or dead bug.

However you add split squats to your workout regime, as long as your form is sound, your booty will thank you.

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Make your workout a healthy (and fun!) everyday habit.

The new year is the perfect time to finally set up that home gym you've been wanting—and when it comes to at-home workouts, a good treadmill is pretty much essential. Rain or shine, a treadmill will make it easy to get your steps in (no excuses!). Whether you're after the latest high-tech features or would be content with a more basic, budget-friendly model, these are the best treadmills in every price range for 2019.

Treadmills under $3,500

• 3G Cardio Elite Runner Treadmill ($3,399; amazon.com). Pricey? Yes. But serious runners will love this treadmill, which is truly gym-quality. Features like an Ortho Flex Shock suspension system, 4.0 HP motor, large 22"x62" running platform, and amazing 10-year warranty make it one of the best out there. Plus, you can get free assembly when you purchase on Amazon right now.

Treadmills under $2,000

• Nautilus T618 Treadmill ($1,229, marked down from $2,199; amazon.com). As far as treadmill discounts go, this is a big one. Not only is the Nautilus T618 40% off on Amazon right now, but you can also get free expert assembly (an $83 value). This model has tons of bells and whistles, including 15% motorized incline, dual backlit LCD display, 20"x60" belt, and Bluetooth connectivity with the Nautilus Trainer 2 app. If you're the competitive type, you can even sync your workout to the RunSocial App to "run" different routes with other users in real time.

• ProForm Pro 2000 Treadmill ($1,219; walmart.com). The ProForm Pro 2000 has a seriously impressive console system. Think: 32 workout settings, 7" backlit display with all your stats, iFit technology, and a built-in EKG heart rate monitor. More than 200 five-star reviews don't hurt either.

Treadmills under $1,000

• Gold's Gym Trainer 720 Treadmill with Power Incline ($599; walmart.com). A Walmart exclusive, this Gold's Gym treadmill offers impressive functionality for the price. There are 18 different one-button workout apps, LED display, a sound system for your music, and a roomy 20"x55" tread belt. Also good? AirStride Cushioning (your joints will thank you), a built-in fan, and incline up to 10%.

• NordicTrack T 6.5 S Treadmill ($599; amazon.com). NordicTrack treadmills are incredibly popular for good reason: They're a trusted brand and a great value. This model is no exception. It's chock-full of features to let you customize your workout experience, including 20 built-in workouts, a console sound system, and access to iFit (plus you'll get a free one-month trial membership). And like the Gold's Gym treadmill, it has a 20"x55" tread belt, which is pretty spacious for the price.

Treadmills under $500

• Confidence Power Trac Pro 735W ($230; amazon.com). It's hard to beat a treadmill under $300, and this affordable model still makes it easy to fit in a serious cardio session. There are 12 built-in workout modes, quick-select speeds, an LED display with your stats, and three manually adjustable incline levels. It can also fold into itself for storage.

• Weslo Crosswalk 5.2t Folding Total Body Workout Treadmill ($269, marked down from $399; walmart.com). If you're after basic treadmill functionality and easy storage, this is the model for you. Reviewers rave about the bonus CrossWalk arms, which let you strengthen your upper body with every step. There are four built-in workout modes, two manual incline positions (1.5% and 6%), and a heart rate monitor. And although the tread belt isn't as big as others on this list, its smaller size means it can be folded vertically so you can store it when it's not in use.

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On Sunday, Nov. 1, 2009, some 40,000 runners sweated their way through the New York City Marathon. To inspire future generations of runners, we’ve assembled some of the most memorable photos from marathons past.

Between the hit of endorphins, the post-flow savasana bliss, and the knowledge that you did your body and mind a solid, working out should make you feel good.

But from time to time, you may find that while chasing that runner's high or back squat PR, you suddenly find yourself keeled over, wanting (or worse, needing) to puke.

This common phenomenon is known as exercise-induced nausea, and it’s a bit like vaginal soreness after a weekend-long sexcapade: annoying but normal, undesirable but treatable, and one of those things that just happens to some women more than others. Here's what you should know about why it's happening, when you should worry, and what you can do about it.

First things first: It doesn't mean you're out of shape

There’s a misconception that getting queasy during or after exercise is an indication of your overall athleticism. But that’s not true. “From beginner exercisers to Olympians or endurance athletes, exercise-induced nausea can affect anyone," Brian Babka, MD, sports medicine specialist and team doctor for Northern Illinois University Athletics, tells Health.

RELATED: 7 High-Intensity Interval Training Mistakes You're Probably Making

"It’s not really related to how conditioned you are,” Dr. Babka says. In fact, a small study published in Appetite in 2001 concluded that training did not decrease exercise-induced nausea.

So if your fitness level isn’t the cause of exercise-induced nausea, what is? Experts say your digestive system is to blame. More specifically, exercise interferes with the the gastrointestinal (GI) tract, which can result in symptoms like nausea, vomiting, and queasiness.

When you boost workout intensity, your gut can suffer

When you’re working out, blood flows to the muscles you're moving and the critical organs that are working—like the heart, lungs, and brain. That means there's less blood being distributed to the digestive organs, which puts a pause on the processes that break down food in your stomach. 

This process is important from a survival standpoint, Michael Richardson MD, a family physician at One Medical Group in Boston, tells Health. "Digesting your food probably comes secondary to running away from a bear," he points out. But in today's world—when we're usually running for fitness or for fun—it mainly becomes an unpleasant side effect.

RELATED: 9 Best Workouts to Do When You Have Your Period

According to Dr. Babka, some workouts command more blood flow away from the GI tract than others. And the more blood that's diverted, the more intense your symptoms will likely be.

“Due to the size of the muscles in the lower body—like the hamstrings and quads—and the overall volume of a leg-day workout, leg day may leave you more prone to this sensation,” he says. High-intensity interval training (HIIT) can also exaggerate this response. 

However, it’s important to recognize that high-intensity workouts or leg day aren't necessarily better (or worse) than other forms of exercise, says Dr. Babka, or that nausea is the sign of a really good workout. High-intensity CrossFitters, endurance athletes, and power lifters may be at higher risk of exercised-induced nausea, he says, but "it's simply a symptom of lack of blood flow—or an indication that you didn’t choose a good pre-workout meal."

Yup, what you eat and drink beforehand matters

“The largest factor in whether or not you’ll experience this nausea is what and when you ate ahead of time,” says Dr. Babka. Jim White, RDN, an exercise physiologist and owner of Jim White Fitness and Nutrition Studios in Virginia, agrees.

“Eating too close to your workout won’t give your digestive system enough time to start breaking it down, but eating too early may result in your feeling hungry and sluggish,” White tells Health. “Everybody is different, but eating one to three hours before working out is the suggested window to prevent abdominal discomfort while still fueling your performance.”

RELATED: All the Gear You Need to Get in Shape in 2019

Foods high in saturated fat—bacon, French fries, and burgers, for example—take longer to process in the stomach, so the delay in digestion can create a “deadweight” feeling. “Fatty and greasy foods also stimulate your body to secrete bile to help digest the fat," says Dr. Richardson. "This bile can add to the gastric pressure and worsen nausea."

White adds that other foods can add to GI distress, "including spicy foods, items containing caffeine, and highly acidic foods.”

So what should should you eat? Focus on lean protein and complex carbs, which will fuel your workout, suggests White. He recommends a slice of whole-grain toast with almond butter, a banana with low-fat Greek yogurt, or a cheese and turkey roll-up.

Dehydration is another possible culprit of exercise-induced nausea, says White. "During exercise, the body loses water through sweating in an effort to cool down," he says. "So not drinking enough water ahead of time can increase the symptoms." The solution is straightforward: Drink water at a steady rate throughout the day.

What if you get nauseous mid-workout? 

If you’re in the middle of a workout and nausea hits, Dr. Richardson says it shouldn’t be ignored. “Often, nausea is our body signaling that we are pushing ourselves too hard or that you’re not resting enough between sets,” he says.

To calm the queasiness, dial back on your intensity and try walking around at a slow or moderate pace. “If you stop exercising too quickly, the nausea may get worse because there will be a massive change in where the blood flow is going in a short period of time,” says Dr. Babka.

That’s one reason many running races have participants walk down a shoot after they cross the finish line, he explains. If you’re in a group fitness class, try walking to the water foundation or taking a step back and walking in place.

The bottom line? Exercise-induced nausea isn't fun. But if it only happens once in a while—and it's not accompanied by more serious symptoms like fever, really bad muscle cramping, chest pain, a complete lack of sweating, or brown urine (which is a sign of the a dangerous condition called rhabdomyolysis)—Dr. Babka says it’s probably not something to be too concerned with.

If you constantly find yourself feeling nauseous, on the other hand, talk to your doctor to rule out more serious medical conditions. Or, try scaling back your workouts: You may be over-training, and your body may be telling you to take it easy. 

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