Interval training is a high-intensity work-out which uses extreme bursts of energy. This gives you the ability to use a lot of energy in one session because the duration is shorter so the intensity can be higher.
Basically, interval training a mix of stop and start exercises which gets your heart racing and then slows, allowing you to catch a breath and get ready to go again. It means you have to work twice as hard for a few minutes with rest periods in between your interval sets.
Researchers have found that these short blasts of exercise are as good as hours of training. This is great news as in our current time-poor society it's important to pack as much punch into your sessions as you can.
Exert hard busts of energy and try 10-second sprints with a five-second break in between to really get your heart racing and work the butt. It's also great for increasing your fitness levels. And the best bit is it burns kilojoules fast.
The stars have been using this method for years it's their secret to staying thin. We spoke to Reese Witherspoon's personal trainer, Michael George, who's famous for whipping stars into shape.
George said he regularly pushes the lean-legged star through interval training outdoors as Reese doesn't like to work out in the gym. Her interval training mainly includes spurts of running and hiking and he also mixes in strength-training exercises like squats and lunges.
Australian personal trainer Joel Costello says interval training rapidly increases your heart rate and metabolism for up to an hour after training.
"This is known as the 'caloric after-burn' and is a great way to burn extra body fat without actually doing any extra exercise," Costello says.
"Short bouts of exercise also allow you to have time to do different types of training at one time."
Resistance training combined with high-intensity cardio sessions improves metabolism and body function, increases lean muscle mass, leaving you feeling "strong, vital and invigorated and turns you into a fat burning machine," Costello says.
"I push all my clients up hills and with interval training, either on a bike [standing in the seat and sprinting up hill] or running on the treadmill on an incline for one minute and then walk up the incline for another minute. Sprints up a hill in the park are also an ideal fat-burning solution," Costello says.
It's also known that short bouts of exercise won't lead to severe hunger pangs after exercising.
"When doing long duration cardio exercise your body will instantly crave a lot of food you will feel ravished and eat anything you can find interval training won't have the same effect, Costello says.