The decision to exercise is always a smart one. Research confirms that anytime you work up a good sweat, you reap physical and mental rewards. But while you don't need fancy equipment or a personal coach to get in a workout, you do need to do your exercises correctly if you want to avoid injury and make the most of your efforts.

There are a surprising number of exercises that seem simple but are actually harder than they look. And if you're going to all the trouble of putting on your workout clothes and lacing up your sneakers, you might as well make your sweat count. Here are nine exercises that you're probably doing incorrectly (and tips from the pros on how to get them right).

1. Stretching

Man and woman stretchingMost people don't realize it, but you need to get limber before you stretch. (Photo: Jacob Lund/Shutterstock)

Wait, what? How is it possible to get stretching wrong? Many people either skip the stretches altogether, or attempt some quick knee jerks or toe touches on cold muscles to "limber up" before a workout. Both of these options are a recipe for disaster. Stretching should be an integral part of your workout, beginning with dynamic stretches — such as arm circles or leg swings — to ease your muscles into motion, and ending with static stretches — such as sitting toe touches — to lengthen a muscle before or after your workout.

One stretch that many folks get wrong is the hamstring stretch (you know the one where you bend from the waist and try to touch your toes.) Rachel Straub, co-author of "Weight Training Without Injury: Over 350 Step-by-Step Pictures Including What Not to Do!" told us "If you are not capable of bending over without rounding your back, you should not be doing this at all!" Instead, she recommends lying on your back while stretching the hamstrings to avoid injury.

Here's how to get all of your stretches right:

Don't:

  • Bounce
  • Stretch without warming up
  • Stretch an injured muscle
  • Be overly aggressive with your stretches

Do:

  • Start with dynamic stretches (high knees, arm circles, hip circles, leg swings, etc.)
  • Alternate stretches day-to-day
  • Gently move through stretches

2. Lunges

Woman doing lunges If your front knee extends beyond your toes, you could be putting yourself at risk for injury. (Photo: Veles Studio/Shutterstock)

Lunges are a fantastic exercise for your glutes and hamstrings. But they are also incredibly easy to get wrong. And bad form on a lunge doesn't just look sloppy, it could also lead to injury. So this is one exercise that you're better off skipping unless you know how to do it correctly. Here are some tips from Anastasiya Gorshkova, fitness instructor and host of a popular YouTube fitness series, on how to do a proper lunge:

Don't:

  • Lean forward or back
  • Lunge too far forward
  • Turn your foot inward
  • Externally rotate the back knee

Do:

  • Keep your body straight the whole time
  • Move your knees in a straight line
  • Try different lunge variations

3. Crunches

woman doing crunch or situp When doing crunches or situps, be sure to keep your lower back straight. (Photo: Uber Images/Shutterstock)

"If you are doing situps, you shouldn't be," said Straub. She explained that situps exacerbate postural problems by rounding your back. "Also, situps place high loads on the lumbar spine and can lead to disc herniation," she added.

You don't need to forgo crunches and situps altogether, but they shouldn't be the only part of your core routine. Mix them in with moves such as the Pilates hundred or yoga's boat pose to build strength and reduce your risk for injury.

This video goes over the proper technique for situps and crunches:


4. Pullups

Men doing pull ups To get a pullup right you need to concentrate on control and form. (Photo: bikeriderlondon/Shutterstock)

According to Straub, a common error when attempting pullups is to pull the weight behind your head, which can lead to rotator cuff issues. If you're not ready for controlled pullups or chinups with good form — and let's face it, most of us aren't — see if you're gym has a lat pulldown machine. These are great for building strength while you're working toward the pullup goal. Here's how to get those pullups right:

Don't:

  • Swing your lower body to create momentum
  • Jump to get yourself to a higher level
  • Cheat by going only halfway up or down

Do:

  • Keep your movements slow and controlled
  • Lift with your palms facing you (for chinups) or away from you (for pullups)
  • Aim to complete the full range of motion

5. Planks

woman doing a plank exercise When planking, lower your hips and look straight ahead. (Photo: George Rudy/Shutterstock)

It seems like everyone is planking these days, but that doesn't mean they're doing them correctly. Planks can build core strength and relieve lower back pain, but when done incorrectly, they can exacerbate these problems. Here are some tips from Gorshkova to help you nail your next plank:

Don't:

  • Arch your back
  • Lower your hips
  • Look up or straight ahead
  • Reach your butt to the sky
  • Tilt your hips
  • Position your hands too far apart

Do:

  • Lock your pelvis to your abdomen by squeezing your glutes
  • Focus on your breathing
  • Try different plank variations

6. Pushups

Woman doing push ups You can vary your pushup workout by changing your hand position. (Photo: Stas Tolstnev/Shutterstock)

Similar to planks, it's easy to lose proper form when doing pushups. This exercise is tough, and many people like to cheat it by slouching or only bending the arms a little bit. But these shortcuts won't get you anywhere when it comes to building strength. The key is to keep your body locked by squeezing your glutes and engaging your core. Here are Gorshkova do's and dont's to help you get the most out of your pushups:

Don't:

  • Perform half a pushup (not going low or high enough)
  • Hold your breath
  • Hold your chin too close to your chest
  • Place your hands too far forward

Do:

  • Keep your elbows closer to your body
  • Keep your body in a straight line from your shoulders to your heels
  • Make sure you are completing full reps
  • Keep your head in line
  • Try easier pushup variations to build up your strength

7. Squats

Woman doing squats Don't let your knees cave inward when you are performing squats. (Photo: Olena Yakobchuk/Shutterstock)

Squats are a great exercise for building strength and stability, but they are also oh-so-easy to do incorrectly. Many people perform squats like they're trying to bump the floor with their butts, but what you should be doing is trying to find an imaginary chair for your butt to sit in. Your weight should be on your heels, helping you engage your glutes and hamstrings, not on your knees where it is bound to cause injury. These tips from Straub explain what not to do when working on squats and how to make the exercise work for you:

Don't:

  • Place your feet too close together
  • Lean too far forward
  • Allow your knees to cave in toward one another
  • Use too much weight

Do:

  • Keep your back straight and your core engaged
  • Look straight ahead
  • Try different squat variations

8. Bicep curls

Woman doing a bicep curl Bicep curls seem simple, but they can be deceptively difficult to get right. (Photo: Uber images/Shutterstock)

On its own, the bicep muscle really can't lift as much weight as it can when it works in conjunction with the rest of the body. So the biggest mistake that people make with this exercise is to try to lift a heavier weight than their bicep alone can handle. This requires tapping into other muscles (like the legs and lower back,) defeating the whole purpose of the exercise. Here's what to watch for when doing your bicep curls:

Don't:

  • Swing the weight or your body
  • Bend at the wrist
  • Flare your elbows

Do:

  • Lock your elbows to your sides
  • Squeeze your bicep as you curl the weight up
  • Control the movement as you lower the weight down
  • Aim to complete the full range of movement

9. Walking

Walkers Think you know how to walk? Think again. (Photo: Rawpixel.com/Shutterstock)

Is it possible to walk incorrectly? Sadly, it is. Sure you can flop yourself around if you're just trying to get from place to place. But if you want to enjoy the health benefits of a good walk, you should pay closer attention to your form. Here are some of the key points to keep in mind. (For more details, check out this post):

Don't:

  • Slouch
  • Pound your feet into the pavement
  • Watch your feet while you walk

Do:

  • Look straight ahead
  • Gently engage your core
  • Relax and enjoy your walk