Not a fan of cardio? Jennifer Aniston's simple 15-15-15 workout is the way to get it done quickly

The 15-15-15 workout goes by so quickly, you more or less break a sweat and then you're finished. At least that's what it feels like. This is the workout for anyone who'd rather be doing anything else than cardio exercise.

Plenty of evidence suggests that heading out in your running shoes, jumping on the bike, or getting 10,000 steps in at home is the way to better health. Recent research even suggests that having good aerobic fitness, which comes from cardio exercise, is more important than BMI for long-term health and longevity.

But, it's not everyone's favourite - and, while the benefits are undeniable, the good news is you don't have to do it for long to reap them. No one knows this better than Jennifer Aniston. In an interview with InStyle, the health-conscious A-lister said she started following the 15-15-15 workout after an injury meant she could only do a Pilates workout and while she "absolutely love[s]" this exercise, she was "missing that kind of sweat when you just go for it."

"I'm going back to my 15-15-15, which is a 15-minute spin, elliptical, run. And then just old school: I can chase myself around a gym," she said.

Want to give it a go for yourself? As woman&home's digital health editor and fitness instructor, I've unpicked all you need to know about the workout with the help of a certified personal trainer.

The 15-15-15 workout: What is it?

As described by Jennifer Aniston, the 15-15-15 workout is a 15-minute spin, a 15-minute session on the elliptical (also known as the cross trainer), and a 15-minute run on the treadmill. Overall, the workout is 45 minutes long and the exercises are done back to back.

There are no time or distance goals to aim for, making it a great cardio exercise for beginners looking to improve their aerobic fitness, boost endurance, and potentially lose weight, given the calorie-burning potential of these exercises.

Sarah Campus, personal trainer, cardio and strength specialist, and founder of LDN MUMS FITNESS, suggests dividing the 15-minute sessions up like so: "Plan your intensity levels ahead of your workout. Begin at a steady state or moderate intensity, then onto the second 15 mins, look to maintain or increase intensity, and same with the third 15 mins, but use the final minute to cool down and stretch at the end," she says.

I tried the 15-15-15 workout

To see what it was all about, I tried the 15-15-15 workout for myself, three times over the past week. I don't mind cardio exercise and I enjoy running outdoors - but even I could see the benefits of this quick session.

Overall, the time efficiency was what I loved most about the workout. As you only spend 15 minutes on each machine, the time passes very quickly - especially so if you have other distractions, like music or a podcast in your headphones, as I do - and I found that I wasn't fighting the same feelings of boredom as I do during a standard treadmill workout sometimes.

On busier days, I appreciated that I could break up these intervals. For example, on my second day of the 15-15-15, I wanted to do a dumbbell workout so I added my 15 minutes of treadmill work as a warm-up and 15 minutes on the bike at the end, to cool down and stretch out my legs. I skipped the elliptical and took a brisk 20-minute walk outdoors to clear my mind after work.

However, it does get repetitive. While you're not doing endless cardio and you are getting more cardio into a routine, I couldn't see myself sticking to the routine in the long term. I would get bored doing it for more than a few weeks. To prevent this, I'd set myself a challenge - how far could I run/cycle in that 15 minutes? How many steps could I get in on the elliptical? I'd also switch out one of these exercises for another cardio workout sometimes - like a Stairmaster workout or stint on the rowing machine - when it got too repetitive.

Benefits of the 15-15-15 workout

1. Boost cardiovascular health

The 15-15-15 is designed to get the heart pumping with more oxygen circulating around the body, boosting cardiovascular fitness.

Between the indoor bike, the treadmill, and the elliptical machine, almost every set of muscles in the body is covered - including the upper body and core - as well, making this a full-body workout.

The NHS recommends that every adult does 150 minutes of moderate-intensity exercise per week for cardiovascular fitness. That's 150 minutes of exercise at 50 to 60% of your maximum heart rate (220 minutes minus your age). If you follow the 15-15-15 workout, you'd only have to do it three times to meet the requirements for the week.

2. The 15-15-15 workout is time efficient

Being only 45 minutes long in total, the 15-15-15 workout is very time efficient. Campus agrees this is one of the main benefits of the workout. "It feels less like traditional cardio. It has more variety with shorter segments, making it feel dynamic and less like you're doing endless cardio, which can be boring and monotonous for some."

Plus, the fact it's time efficient means it's easy to stick to. "Consistency and sustainability are the most important thing and a varied and manageable routine is more likely to become a habit," she says.

To work out if you're in the right heart rate zone, you can use the monitors on the machines - or invest in one of the best fitness trackers, which will likely be more reliable as these take a continuous heart rate throughout your workout.

3. The indoor bike and cross trainer are light on the joints

One of the most common complaints of cardio exercise is how it impacts joints in the knees, hips, and ankles. With the 15-15-15 workout, only one of the three exercises involves loading your joints.

The indoor bike and cross trainer are light on the bones and joints, making them a good option for those who experience discomfort in this area, says Campus. "Women can lose up to 20% bone density as they go through menopause, so doing this lower impact workout gives women the benefits without putting their bodies through too much stress," she adds. "It can also support your mental health without risking impact injuries."

4. Versatile

While the traditional 15-15-15 workout involves doing the exercises back to back, there's no reason why you can't do these over the day. This is what's known as exercise snacking and it has some benefits for heart health, physical function, and mental health, per research linked to UNSW Sydney.

Also, as noted, you can swap out different cardio machines and exercises to suit your schedule and mood. For example, walking briskly for 15 minutes is just as good as 15 minutes of steady running on the treadmill.

"The 15-15-15 workout can boost endorphins without you feeling overwhelmed," says Campus. "You can still enjoy the mental health benefits of cardio, such as [improved energy], mood, and stress relief without feeling stuck in a repetitive activity."

Sarah Campus

Sarah Campus is a highly qualified women's PT and Nutrition Coach. She is a runner, mum of 3, and the founder of holistic wellness platform LDN MUMS FITNESS.

She is a Level 2 and Level 3 NASM qualified Personal Trainer and Gym Instructor, and has completed programmes in Exercise and Nutrition, Exercise Referral/GP Referral, Exercise Ante and Post Natal, Exercise for Older Adults, Bootcamps and Circuits, Advanced Fitness Testing, Free Weights, Indoor Group Cycling.