A Personal Trainer Reveals the 2 Biggest Mistakes Women Make in the Gym

If there's one thing we keep preaching, it's that lifting weights and strength training is important to lose weight, build muscle, make progress, and promote overall health. The problem is, many women are afraid if they lift heavy weights, their muscles will get too big and bulky, Jim said.

"Muscle is attractive; too much body fat can cause health implications and increase disease risk," he told POPSUGAR. In fact, he explained that men and women start losing an average of 8 percent muscle mass each decade after age 40 if they don't weight train.

And instead of being too "bulky," lifting heavy weights will give you sexy muscle definition that you won't get with cardio alone. "Most women don't have enough testosterone production in their body to put on huge muscle gains and 'get big,'" personal trainer and holistic health coach Lauren Clare, NASM, told POPSUGAR. Testosterone is one of the primary hormones that promotes muscle growth.

To reap the benefits of weight training, Jim recommends women strength train three times a week for progress and two times a week for maintenance, and to focus on full-body workouts.

It's important to find a workout you like so you keep doing it and stay committed to your fitness goals. However, it is possible to have too much of a good thing.

"I see a lot of woman who are just runners or who just lift or just Spin," Jim told POPSUGAR. "It is important to get a variety of exercise disciplines in to decrease boredom, work different muscles, improve flexibility, and engage the heart." So if Spinning is your workout of choice, try doing it a couple days a week interspersed with days of weight training instead of just going to Spin class five days a week.

"A well-rounded program includes strength, cardiovascular activities, stretching, balance, and agility, to name a few," he explained.