Fitness and exercise are more popular now than they have ever been. This is not surprising, given all the benefits of physical activity, such as weight loss, better mental health, and a lower risk of chronic diseases. However, with the growing popularity of (primarily) indoor workouts like weightlifting, CrossFit, Pilates, and yoga, there is growing room for doing harm to our bodies.

I recently got in touch with health and fitness experts from around the U.S. to find out what they consider some of the most common exercise mistakes. Whether you’re a seasoned pro or a total fitness newbie, chances are you’re making one of them. Take a look at their solutions for help on correcting some of these fitness mistakes:

1. Poor form on simple abdominal crunches

According to Tami Peavy, owner of Practical Therapy4U, keeping your hands behind your head or straight at your side during common ab crunches places an unsafe amount of torque on your neck. This can lead to neck pain, migraines, disc bulging and shoulder pain.

Instead, Tami recommends the “Reverse Crunch.” She explains, “Lying on your back, put your hands under your lower back for support. Bend your knees and keep your feet flat on the floor. Now, lift your knees into your chest, contracting your stomach muscles as you lift. Repeat this 10 times for two sets.” It makes for an effective, low-stress alternative!

2. Static stretching before a workout

Stretching is a good thing, right? It certainly has its place, but it can also be damaging, says Pilatesology co-founder Alisa Wyatt. “Stretching is great after a workout, but if you do it when your muscles aren’t warmed up, then it gives you what I call ‘old rubber band’ muscles. This is when your muscles stretch to the point of weakness and stay that way while you work out, which reduces your strength and power, as well as sets you up for injury.”

Instead of kicking off your workout with a cold stretch, she recommends a warm-up that gets your blood moving, your joints lubricated, and helps increase your flexibility all at the same time.

3. Too much running, too hard

Running is one of the most popular forms of exercise, with minimal cost and benefits that include a stronger heart, lungs, and core. But too much of a good thing is still too much.

“Because of its repetitive nature, running has the potential to cause overuse type injuries to the feet, lower extremities, legs, and spine,” says Joel K. Jezequel from NY Sports Med. He recommends steady increases in distance (about 10% per week, optimally), addressing muscle strength/length imbalances, and getting sufficient rest between runs.

4. Too much sitting

From long hours sitting in front of the computer, to driving in our cars and lounging on the couch at the end of a long day, the last thing most of us need is more time spent sitting—especially during our workouts.

“Sitting down to train the shoulders, biceps and back are traditional ways to work those muscles, but it decreases the work for the legs and the core,” explains fitness expert Keli Roberts. “Training in a standing position allows the legs and the core to play a role and is a much better and functional approach to exercise.” She also points out the strong association between extensive time spent sitting and increased mortality risk, according to research from the Pennington Biomedical Research Center.

5. Generating movement from the joints, rather than the muscles

One of the many downsides of poor form is placing too much pressure on the joints, rather than the muscles. This issue, according to CABARRET creatrix Nicole LaBonde, often stems from “bending and unbending at the joint, rather than thinking of lengthening or contracting (the) muscles.” In order to correct this problem, she will often force students to perform movements in slow motion, keeping the muscles engaged and the joints stress-free.

6. Choosing the wrong workout routine

“The biggest mistake I see people make is doing things they hate,” says Jeanette DePatie, author of The Fat Chick Works Out! “Into every life comes the decision to watch Game of Thrones or do your fitness routine. If you hate your exercise routine, I guarantee, ‘winter is coming.’ I often say exercise is like sex; if you’re not having fun, you’re not doing it right!”

7. Not enough intensity during workout time

It goes without saying, but the goal of most exercise routines is to burn calories and lose weight. And it turns out that most of us are doing it wrong. According to personal trainer and fitness author Clint Fuqua, “EPOC (excess post-exercise oxygen consumption) is the real trick to burning off unwanted fat, increasing stamina for all activities, and being able to enjoy that extra slice of pie with no regrets.” If you’re looking to trigger this long-term post-workout burn, Fuqua recommends pushing hard for 30-40 minutes, rather than hanging around the gym for an hour or more, barely breaking a sweat.

8. Listening too much to the internet, magazines, and books

If you’ve done much research into diet and exercise trends, you’ve probably noticed that the “experts” rarely seem to agree on what’s the best way to lose weight and get healthy. While some are adamantly advising low-carb, high-fat diets, others are all-in on keeping fats down and protein high. The answer may be simpler than you think. Certified strength and conditioning coach Henry Halse says, “You will have much more success if you simply tune out all the background noise and focus on what you know works for you! My dad once gave me the diet advice ‘everything in moderation.’ His mother actually told him that. She didn’t read it in a book, magazine, or Google. It’s something that she knew instinctively. To be honest, researchers are now finding that ‘everything in moderation’ may actually be the most beneficial approach to eating.”

9. Not rehydrating enough during/after workouts

Did you know that dehydration can have negative effects on everything from your mental sharpness to power, endurance, and much more? David Parish, director of Biofreeze Human Performance Center, warns that dehydration “is one of the biggest contributors to stalled healing, yet it is one of the most preventable conditions out there.”

He recommends monitoring your sweat loss and making sure to rehydrate with three cups of water for every pound of water weight you lose. He also warns against alcohol, caffeine, and certain supplements, all of which can contribute to dehydration.

10. Ignoring bone and joint health

While most of us focus on fitness and muscle strength as the foundation of our exercise, that might be the wrong approach. “An exercise routine that places too much stress on the muscles without caring for joint and bone health often leads to serious pain in supporting areas of the body, such as the lower back, knees, and ankles,” says Dr. Steven Kozmary, owner of Kozmary Center for Pain Management.

To avoid these issues, he advises receiving proper nutrition and stretching, and avoiding exercises that place undue stress on crucial joints.

11. Thinking you need a gym membership to get in shape

Think you can’t get a good workout unless you have a pricey gym membership? You’re wrong, says Jen DeCurtins, Premier Protein Ambassador and author of Ultimate Plank Fitness. She points out that “not having access to a gym doesn’t mean you can’t strength train! There are so many workouts you can do at home with your own bodyweight or a set of dumbbells.”

These types of calisthenic workouts are easy to find and can have serious health benefits.

12. Working too hard without resting

Dayna Kurtz, owner of Fitness That Fits You, knows all too well the negative effects that come from over-working. “In a city like New York,” she says, “there is tremendous pressure to look fit. As a result, many clients are inclined to overdo their workouts–hitting the gym multiple times a day, or working the same muscle groups on consecutive days. Muscles need time to rest and repair after strength training.”

She points out that inadequate rest can drastically increase the likelihood of injury and is an essential part of a good fitness regimen.

13. Not lengthening and stretching muscles

Another misstep that’s become all too common is ignoring the need to lengthen and extend your muscles. “What many weightlifters also don’t know is that lengthening muscles (stretching) will help build strength and prevent injury,” says Joey Thurman, a personal trainer and creator of The Lifestyle Renovation. “Tight muscles will not be able to produce the force needed to lift weights to their fullest potential, and therefore will not develop as quickly as they could.”

Overall, there are many exercise mistakes that we’re all prone to making. By being aware of these mistakes and taking steps to avoid them, we can all enjoy safer, more effective workouts.