It is easier to maintain cardiorespiratory fitness with shorter but more intense workouts.

Exercise & Fitness

To exercise in interval-training mode, swim a fast lap, rest, and then swim another fast lap. Image: Thinkstock

It helps build cardiovascular fitness with shorter workouts.

Have you heard about interval training but aren't sure how it works and whether it's right for you? Interval training simply means alternating between short bursts of intense exercise and brief periods of rest (or a different, less-intense activity). The payoff is improved cardiovascular fitness.

"Aerobic or cardiovascular training is designed to develop a healthier heart and circulatory system," says Howard Knuttgen, research associate in physical medicine and rehabilitation at Harvard-affiliated Spaulding Rehabilitation Hospital and a past president of the American College of Sports Medicine. "Some regimen of aerobic training is really essential to good health."

You can give interval training a trial run simply by altering your current workout routine. To get the cardiac boost from interval training, you have to be willing to push yourself close to your limits—at least briefly. Three 20-minute sessions per week could add zest to your exercise experience and enhance cardiovascular fitness.

What is interval training?

Guidelines advise men to strive for 150 minutes of moderate-intensity exercise per week. In practice, that could be 30 minutes of exercise on five days of the week. Brisk walking is a good example of moderate-intensity exercise, but any kind of activity counts as long as it requires some physical effort and raises your heart rate. Guidelines say you can also meet your target with half the amount (75 minutes) of higher-intensity exercise. In this case, the classic example would be jogging or vigorous lap swimming.

That seesaw relationship between exercise intensity and duration is what makes interval training work—but you may need to break a sweat. "High-intensity basically means exercising at a higher intensity or velocity than you could otherwise sustain for five to 10 minutes before becoming exhausted," Knuttgen says. In interval training, "you do high-intensity exercise for a minute, then rest, then repeat."

Some men find pushing their limits invigorating; others find it unpleasant. "A man might think this isn't all that much fun," Knuttgen notes. But remember that you don't necessarily need to stick to interval training all the time. You can, for example, do interval training on one day and switch the next day to longer-duration, moderate-intensity exercise.

Here are a few ways to adapt your normal workout to a session of interval training:

Swimming. Swim one lap as fast as you can. Rest for about the same time as it took you to swim the lap. Repeat.

Walking. Walk as fast as you can for a minute or two. Then walk at a leisurely pace for the same period. Repeat.

Gym machines. Treadmills, elliptical trainers, and stationary cycles often have a built-in interval training function to put you through your paces.

What are the benefits?

Interval training allows you to accomplish the same amount of exercise "work" in less time. That could make workouts easier to fit into a busy day or open a time slot to add some strength training. If you can reduce your moderate 30-minute workout to 15 or 20 minutes of interval training, the cardiovascular benefit should be about the same.

As fitness improves, you should feel better, with greater endurance and more get-up-and-go. However, cardiovascular training doesn't significantly boost muscle strength or power. Knuttgen points out that even elite marathoners don't have unusually strong leg muscles. But their hearts and lungs work together at peak performance.

No matter what type of cardiovascular training you choose, you need to do it regularly to see the improvements. "Three days a week is a good recommendation—more if you can, but not much less and definitely not just once a week," Knuttgen says.

Is it safe?

In an otherwise healthy man, interval training should not present major risks, as long as you don't dive in too fast. "If you haven't done this before, begin slowly," Knuttgen says. "As you find it easier to exercise, you can increase the intensity."

If you have heart disease or high blood pressure, talk to your doctor before starting interval training or any other new exercise program—especially if you've been relatively inactive until that time.

You can reduce the risk of straining a muscle or joint by starting with a gentle warm-up before your workout to loosen your joints and get the blood flowing. Be prepared to "feel the burn" after your challenging new workouts. It's normal to feel sore for a day or two as your muscles recover. A day of time off between workouts is a good general practice.

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Exercise is one of the best ways to boost your heart health and overall wellbeing. But what is the right amount and type of exercise? As with many things, the answer is: it depends. People have different health goals, abilities and limitations, so there is no one-size-fits-all answer. At the end of the day, you have to choose the right exercise for you. This can be daunting with all the options out there, so here are some comparisons of different types of exercise to help you make the best choice for you.

HIIT refers to short, intense, unsustainable bursts of exercise followed by periods of rest, while steady state cardio refers to a cardio workout using continuous, sustained effort, such as running, cycling or swimming. While some claim HIIT is the new magic exercise program, as with most things, it’s a bit more complicated. Research has found that with regard to calories burned, HIIT isn’t much better than a slightly longer period of steady state cardio. Other research has found that HIIT is safe and effective in people with a range of cardiac and metabolic dysfunctions.1 This research also found that HIIT had better outcomes for aerobic fitness but similar ones for metabolic function when compared to continuous moderate exercise.2

So if you enjoy a challenging, short, intense full body workout, HIIT may be for you. With any exercise, but especially this form, make sure you keep a healthy schedule and listen to your body. Around three to four sessions per week is usually sufficient strain and can be combined with less intense exercise on off days if you desire. But if you prefer a chilled workout, have more time to spend on your exercise or are injury prone, then steady state cardio may be a better choice with similar outcomes. Either way, make sure you are maintaining form and staying within your personal ability levels.

Weight training increases weight endurance, muscle tone and strength, and working with free weights can improve stability. Resistance training also helps to maintain bone density, so it is an important part in any exercise program, especially as we age and our bone density begins to decrease. Some research has shown that resistance training may also be more beneficial in increasing the calories burned due to exercise than steady state aerobic exercise.2

Other research has shown similar outcomes in weight management when either resistance training or aerobic training was used in conjunction with a healthy diet. However, aerobic training appeared to have greater benefit in reducing body fat and improving cardiorespiratory fitness, while resistance training seemed to be better at building muscle.3

So should you focus on aerobic training? Resistance? Both? Research on the effect of aerobic, resistance and combined training on cardiovascular disease risk factors found that in people at risk of cardiovascular disease, a combination of resistance and aerobic training seemed to have better results on the factors measured (which included blood pressure, cardiorespiratory fitness, blood glucose, body composition and strength) than aerobic or resistance training individually.4, 5

Other research suggests that a combination of resistance and aerobic training is one of the best options to assist in managing diabetes.6 Combination exercises appear to help maintain blood glucose control and modulate other cardiovascular risk factors.

If you want to find the best exercise for you, trying a range of different exercises and working out what you enjoy most, as well as trying to incorporate a range of activities, seems to work best. You may also want to consider the following factors.

1. Do you enjoy the exercise? This is one of the main elements that determines if someone will continue to do exercise, so choose something you enjoy rather than the “right” kind of exercise. Also choose something that incorporates some form of aerobic element as well as weight bearing/resistance.
2. Can your body handle the exercise? For example, HIIT may not be the best for someone just starting to exercise or recovering from a heart issue.
3. Is it easily accessible and does it fit your schedule and time limitations? Avoiding potential road blocks in your exercise program is easier than overcoming them. One reason programs like F45 have become so popular is that less time is required and they are more available.
4. Will being held accountable help? For those who might need some extra support, joining an exercise group or getting a personal trainer could be just the motivation needed to stick to their exercise program.

1. Kessler HS, Sisson SB, Short KR. The Potential for High-Intensity Interval Training to Reduce Cardiometabolic Disease Risk. Sports Medicine June 2012 1;42(6), pp 489-509.
2. Milanovic Z, Sporis G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for V02max Improvements: A Systematic Review and Meta-Analysis of controlled Trials. Sports Med. October 2015, 45(10) :1469-81.
3. Said MA, Abdelmoneem M, Almaqhawi A, Hamid Kotob AA, Alibrahim MC, Bougmiza I (2018) Multidisciplinary Approach to Obesity: Aerobic or Resistance Physical Exercise. J Exerc Sci Fit December 2018, 16(3), pp 118-123.
4. Greer BK, Sirithienthad P, Moffatt RJ, Marcello RT, Panton LB (2015) EPOC Comparison Between Isocaloric Bouts of Steady-State Aerobic, Intermittent Aerobic, and Resistance Training. Res Q Exerc Sport June 2015, 86(2), pp 190-195.
5. Schroeder EC, Franke WD, Sharp RL, Lee DC (2019) Comparative Effectiveness of Aerobic, Resistance, and Combined Training on Cardiovascular Disease Risk Factors: A Randomized Controlled Trial, PLoS One January 2019, 7;14(1).
6. Armstrong MJ, Colberg SR, Sigal RJ (2015) Moving Beyond Cardio: The Value of Resistance Training, Balance Training and Other Forms of Exercise in the Management of Diabetes. Diabetes Spectrum February 2015, 28(1), pp 14-23.

Susan Tyfield is an evidence-based chiropractor who utilises a wide range of treatment techniques and rehabilitation in her sessions. She has been practicing for over 13 years, having achieved board certification both in South Africa, where she had her own private practice, and in Australia, where she has practiced since 2011. She has special interests in sports and performing arts healthcare as well as chronic pain management. She practices out of Waterloo and Darlinghurst, Sydney NSW.

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