A top personal trainer shares 3 common mistakes people make when trying to build muscle

Harley Pasternak strength trains for 20 minutes, six days a week.

Harley Pasternak The celebrity trainer Harley Pasternak says common gym mistakes can hold back muscle gains.

Progressive overload is key to building and maintaining muscle.

Pasternak said that giving muscles enough time to recover between workouts is essential.

Harley Pasternak has spent 30 years helping people build strength and muscle.

In that time, the 51-year-old Los Angeles-based personal trainer, who has worked with Kim Kardashian , Rihanna, and Robert Pattinson, has seen people making the same mistakes, which keep them from making the gains they want to see.

Progressive overload , which means challenging your muscles more and more over time, whether through heavier weights or more reps, is crucial to building muscle , but there's more to it than just that, Pasternak told Business Insider.

Rest and a thoughtful workout plan are also important if you want to build muscle, he said.

For Pasternak, that means strength training for 20 minutes , six days a week, and focusing on two muscles per workout.

Pasternak shared the common mistakes he sees people make.

Worrying about looking 'bulky' Pasternak said he often sees women holding back when lifting weights because they are worried about looking "bulky." "It's very difficult to put on muscle," he said.

Building muscle requires eating more food than you burn, also known as a calorie surplus.

Regardless of how it changes your body shape, lifting weights also carries many health benefits, including reducing the risk of osteoporosis .

Doing full-body workouts Pasternak isn't a fan of full-body workouts if people want to build muscle.