3 personal trainers share tips they wish they'd known when they started working out

• Three personal trainers said beginners often make similar mistakes that cost them time and progress.
• Going to the gym with a plan can help keep you on track, as well as motivate you.

It can take a long time to fine-tune your workout routine. Over time, you learn which exercises work best for you, how to create a routine that suits your goals, and — hopefully — you're constantly checking in on your form to prevent injuries. But wouldn't it be nice if we could start our journey with exercise already having all the answers?

One way to cut down the trial-and-error period is to talk to an expert, the personal trainer Chrissy Signore told Insider. She said that after years of exercising and working as a personal trainer, she's learned so much she wishes she'd known when she first started. Now she shares these tips with her clients.

Like Signore, the personal trainer Stefanie Tsengas and the celebrity trainer Harley Pasternak told Insider they made many mistakes when they began working out that they wish they could go back and fix. They said they also give beginners the advice they wish they had when they first started.

These personal trainers told Insider that making a plan and properly warming up are essential at the start of a new exercise routine, among other tips.

Make a plan with flexible goals

All three trainers agreed that a mistake many beginners make is going to the gym without making a proper workout plan. Your plan should include strategic exercises that work toward longer-term goals, Pasternak said.

Not only will a plan help you make progress toward your goals in the long run, it will also help you feel accomplished and motivated, as exercise physiologist Tom Holland previously told Insider.

While setting goals for yourself is important, Signore also said it is important to be flexible with these goals and change them as you progress. You may think you want to lose 10 pounds, she said, but gaining muscle through exercise might mean fat loss doesn't show up on the scale the way you thought.

Less is actually more

Another common mistake the personal trainers see in beginners — and even did themselves — is trying to do too much.

"I have clients who think they have to work out and lift six to seven days a week on top of doing like an hour of cardio. They overdo it with volume, volume, volume," Tsengas said.

She also said that many of the people that come to her looking to lose weight have the same strategy that she had when she started working out, which is to "overtrain and undereat." This approach can actually have the opposite effect, she said, because it slows your metabolism and pushes your body to hold onto more fat.

Losing weight too quickly — more than about two pounds a week, according to Signore — can also put you at a greater risk of gaining it back.

Pasternak said it's about working smarter, not harder. He said that results come from staying consistent with a long-term plan. And in terms of workout length, he said that his sessions can last anywhere from 15 to 45 minutes, but never longer.

Warm-ups and focusing on mobility will help prevent injury and make your workouts more effective

Tsengas said that one of the biggest mistakes she made when she first started was not warming up or working on mobility. Even at 26, she said she's had consistent injuries that could have been prevented by properly warming up.

Signore said that moving the muscles you're going to work out for a few minutes before you begin your workout and going through the full range of motion without weight can make your routine more effective. After your workout, she said it's also important to stretch.

"The stretch at the end is gonna help your blood flow, which is gonna help with your muscle recovery. It's gonna help with less muscle aching after and reducing injury, because all of those muscles are so tight," she said.

Work on your supporting muscles

Although he admitted that as a teenager, he probably wouldn't have been interested in this advice, Pasternak said that exercising more supportive muscles is important for beginners — specifically the posterior chain, which are all the muscles on the back of your body, like the glutes, triceps, and lats.

Strengthening these muscles will help with your posture, prevent injury, and support the muscles on the front of your body to make them look better, he said.

The 4-0-1 method can help improve your power and muscle imbalances

One tip Signore said she wished she knew when she was starting out was the 4-0-1 method.

She said to aim for four seconds as you lengthen the muscle during any strength-training movement. At the end of that movement, try not to pause, and then contract the muscle for one second.

When you slow down the extension of the muscle, you put more strain on it, she said, as well as strengthen the supporting muscles around it. Then contracting that muscle quickly will help make it more powerful overall.

Develop a deeper 'why' for your exercise

While the trainers said that their goal when they started was primarily aesthetic, it's important to develop a deeper "why" if you want exercise to be a long-term part of your life.

Tsengas said that while looking good is still important to her, she also prides herself on her physical performance and believes that exercise is essential for her mental health.

Signore said her reason for exercising changed after working with a personal trainer.

"I went into the gym with the goal of 'I need to lose 10 pounds,' and I came out of it after working with a personal trainer with the feeling of, 'No, I need to create this sustainable, healthy life,'" she said.

Your goal will ultimately be personal, she said, but developing a deeper reason for why you exercise will ensure it's something you'll stick with for life.