Looking to shake up your strength-training routine? Consider giving peripheral heart action (PHA) training a try. This form of resistance training can make your workouts more efficient, helping you boost your strength and endurance and burn more calories in less time.

And don't worry — the concept isn't complicated! Here's how PHA training works, why it's great, plus a sample circuit to get you started.

Peripheral heart action or PHA training is a type of circuit training that alternates working your upper and lower body. It's much like traditional circuit training, where you move quickly from one exercise set to another. But instead of doing, say, an upper-back exercise followed by a biceps exercise or a squat followed by a leg press, you'd switch between upper-body exercises — like seated rows — and lower-body exercises — like lunges.

Often, PHA training involves switching between exercises that work big muscle groups.

"We tend to do it with compound movements, like squatting and deadlifting, then pressing and rowing," Noam Tamir, CSCS, founder and CEO of TS Fitness in New York, tells LIVESTRONG.com.

This form of training speeds up circulation of your blood from your heart peripherally — aka to your extremities — which ultimately burns more calories and may contribute to gains in lean muscle mass, according to the National Academy of Sports Medicine (NASM).

What's more, PHA training is versatile and highly customizable.

"It's a little like interval training. You can do it for different lengths of time with different rep ranges, as long as you're not taking too much rest in between sets," Tamir says. You can adapt the concept to different fitness goals, too. "You can take a little more rest if you're looking to maximize strength or a little less rest if you're looking to maximize endurance."

In other words, this approach to strength training has something to offer almost everyone.

PHA training has the edge over standard resistance circuits in a bunch of important ways. Here's what you'll get when you alternate upper- and lower-body moves.

PHA training involves moving from one resistance exercise to the next relatively quickly, so your heart rate stays elevated while you work your muscles. This essentially gives you two types of exercise in one — strength and cardio — making it a great option if you don't have much time for working out.

"It's a great bang for your exercise buck," Tamir says. "You're gaining strength, but your heart rate will also be going up quite a bit, so it's also a calorie-burning exercise."

Spending your whole sweat session focusing on either your upper or lower body is a recipe for feeling exhausted fast. But when you switch back and forth, different muscle groups get more of a break (even while you're staying active), Tamir explains. As a result, you can actually go longer and harder.

PHA training keeps your heart rate up, making it an effective calorie-burner. Alternating between upper- and lower-body movements can speed up circulation, which is thought to help decrease body fat and increase lean muscle mass, according to the NASM. "You'll also get that afterburn more efficiently than if you were doing straight cardio," Tamir says, referring to the process where your body continues to burn calories even after you've finished your workout.

PHA training can improve your cardiovascular endurance and your overall ability to carry out everyday activities. "It's great for heart health and for building overall functional strength for things like carrying groceries, carrying your kids, pushing heavy doors open or going swimming on vacation," Tamir says.

In fact, PHA training has been shown to improve aerobic capacity more effectively than intense cardio exercises like high-intensity interval training (HIIT), according to a November 2014 study in the ​European Journal of Applied Physiology​. The benefit is thought to come from PHA training's ability to enhance circulation, which may increase metabolism at the cellular level.

Most healthy people can perform PHA training, according to the NASM. As long as you stick with the basic concept of alternating between upper- and lower-body movements, you can switch up the exercises, weights, reps and sets and rest periods for your fitness level and goals.

"We build people up, starting with certain exercises for three to four weeks and then graduating to something more advanced," Tamir says.

PHA training can be incorporated in place of traditional circuit or strength-training workouts. "You can do it three or four times per week, depending on your [fitness level], how quickly you recover and what you're doing on your off days," Tamir explains. "You generally want to give your muscles about 48 hours to recover."

He recommends doing activities that aren't strength-focused on the other days, such as running, walking, cycling or doing yoga or Pilates.

Want to give PHA training a shot? This circuit workout, designed by Tamir, is made for moderate fitness levels. It requires a set of dumbbells, a kettlebell and an exercise bench. Always get the green light from your doctor before trying a new activity if you're new to exercise.

Perform four rounds, taking 45 to 60 seconds rest between each exercise.

Perform three rounds, taking 30 to 45 seconds rest in between each exercise.

Perform three rounds, taking 15 to 20 seconds rest in between each exercise.