Here's the ultimate 'lazy girl' workout!

Achieving physical fitness doesn't always have to mean spending hours in the gym lifting heavy weights.

A Low-Intensity Sustained State (LISS) cardio exercise can be as essential at keeping you fit as a high-intensity workout.

Personal training experts told Daily Mail Online that walking, swimming, cycling and jogging for up to an hour can quiet your mind while strengthening your heart.

They suggest adding a light workout to your regular routine as it can still help build muscle on your days off from heavy lifting.

While the fitness trend dubbed the 'lazy girl workout' doesn't build strength or muscle as high-intensity exercises do, light workouts do have overall health benefits that are equally as important.

Low-Intensity Sustained State is any form of low-intensity cardio exercise performed for a prolonged period of time - usually for up to an hour.

This type of exercise keeps your heart rate consistent throughout the workout, promoting cardiovascular endurance.

Exercises can range from a light two-mile jog to swimming laps in the pool or going for an hour-long walk with your dog.

This is the opposite of High-Intensity Interval Training (HIIT) that focuses on quick bursts of cardio followed by a rest period.

While many gym fanatics are focused on these high-intensity workouts to build muscle, personal trainer and owner of New York Personal Training Rui Li told Daily Mail Online that you need both in your routine.

"There are a lot of trainers who knock LISS, but if you're focusing on dropping body fat you want a combination of the two," she said.

Training at a lower intensity allows more oxygen to be available to your body and fat needs oxygen in order to be broken down.

That's why Rui suggests LISS on rest and recovery days.

Rui said: "If you are trying to improve overall cardiovascular endurance you will need steady state cardio, but there is always place for high-intensity."

Weightlifters, for example, may have issues catching their breath between sets.

Rui recommends throwing in a couple of days of two-mile runs or rowing to boost their heart's endurance and help them recover from strenuous exercise quicker.

However, ignoring high-intensity workouts will leave you at a plateau and unable to build strength and muscle.

A person first needs strong core and hip muscles before they can engage in highly repetitive workouts, according to Rui.

"No amount of steady state cardio is going to improve that tremendously, so you have to make sure you have strong glutes, hip flexors and deep abdominal in order to sustain those low-intensity workouts," she said.

Kevin Richardson, owner and founder of Naturally Intense Training, suggests LISS may be more of an exercise for your mental health than physical health.

"People go on long walks for the mind and to relax in general," he told Daily Mail Online.

He said: "Physiologically, you can't have adaption from low-intensity because the human body responds when it's doing something it hasn't done before."

If you want to see results, Kevin said you can't have your cake and eat it too.

"I've been doing this for 26 years and every once in a while it's a trend to do as little as possible, but the laws of physics don't allow for us to get a change in body type that way," he said.

Both trainers agree that deciding your workout depends on your fitness goals and doing only low-intensity exercises won't get you an incredibly toned body.

However, pairing it with high-intensity workouts could be the recipe for great health.

This article was first published on Daily Mail and is republished here with permission.