High-Intensity Interval Training

Looking for a way to add variety to your exercise plan while taking your fitness to the next level? High-intensity interval training (HIIT) is a cardio respiratory training technique that alternates brief speed and recovery intervals to increase the overall intensity of your workout. HIIT is used by athletes and everyday exercise enthusiasts to reach performance goals and enhance fitness and well-being.

How does it work?

Most endurance workouts, such as walking, running, or stair-climbing—are performed at a moderate intensity, or an exertion level of 5-6 on a scale of 0-10. High-intensity intervals are done at an exertion level of 7 or higher, and are typically sustained for 30 seconds to 3 minutes, although they can be as short as 8-10 seconds or as long as 5 minutes; the higher the intensity, the shorter the speed interval. Recovery intervals are equal to or longer than the speed intervals.
High-intensity interval training is done at a submaximal level; around 80-95% of maximal aerobic capacity. Sprint interval training (SIT) is a type of high-intensity interval training that pushes beyond this level to 100% or more of maximal aerobic capacity, or an exertion level of 10.

What are the benefits of HIIT?

The payoffs of pushing yourself with HIIT are plentiful, and include:

  • Significantly increased aerobic and anaerobic fitness
  • Decreased fasting insulin and increased insulin sensitivity
  • Reduced abdominal and subcutaneous (just under the skin) fat

The surprising thing about HIIT is that it involves such a small total amount of exercise. By including HIIT in your exercise plan, you can realize remarkable results in a short amount of time, which is good news for busy people.

Is HIIT safe?

High-intensity exercise of any type brings with it a higher risk of musculoskeletal injury and cardiac events (if at increased cardiac risk).  But along with healthy subjects, HIIT has been studied as a training method for people with heart disease and congestive heart failure. Under clinical supervision, subjects were able to tolerate high-intensity intervals without negative effects. Most importantly, they experienced bigger improvements in cardiovascular function compared to those undergoing continuous moderate-intensity training.

The bottom line? Check with your health care provider before adding it to your exercise plan.

How can I get started with HIIT?

Choose an aerobic exercise—like stationary bicycling. Warm up for 5 minutes, and perform just a few alternating speed and recovery intervals; 3-4 of each should be plenty and will give you a feel for it; finish with an easy cool down. Here’s a beginning HIIT example:

Time Interval Exertion Level (0-10)
5 min. Warm-up 3–4
1 min. Speed 7–9
2 min. Recovery 5–6
1 min. Speed 7–9
2 min Recovery 5–6
1 min. Speed 7–9
2 min Recovery 5–6
1 min. Speed 7–9
5 min Cool-down 3–4
22 min. Total Time (add more intervals for greater fitness & weight loss)
(4 min. total speed- beginner HIIT program)

HIIT protocols vary widely. There’s no one best single way to structure them. Experiment with shorter and longer speed and recovery intervals to find what works best for you. Gradually work up to 8-10 or more speed intervals, depending on your fitness goals. Keep in mind that the most common mistake made with interval training is making the recovery intervals too short. Perform HIIT workouts 2-4 a week at most to reduce your risk of injury. This high-intensity training method is best used periodically for up to 6 weeks or so to enhance regular training, not necessarily as a year-round fitness strategy.

For best results, work with a certified fitness professional to create a personalized HIIT training plan. HIIT requires a big, sweaty effort, but if you stick with it, chances are you’ll be rewarded with impressive results.

Additional Resources

High-Intensity Interval Training Is Time-Efficient and Effective, Study Suggests

Mar. 12, 2010 — The usual excuse of “lack of time” for not doing enough exercise is blown away by new research published in The Journal of Physiology.

The study, from scientists at Canada’s McMaster University, adds to the growing evidence for the benefits of short term high-intensity interval training (HIT) as a time-efficient but safe alternative to traditional types of moderate long term exercise. Astonishingly, it is possible to get more by doing less!

“We have shown that interval training does not have to be ‘all out’ in order to be effective,” says Professor Martin Gibala. “Doing 10 one-minute sprints on a standard stationary bike with about one minute of rest in between, three times a week, works as well in improving muscle as many hours of conventional long-term biking less strenuously.” HIT means doing a number of short bursts of intense exercise with short recovery breaks in between. The authors have already shown with young healthy college students that this produces the same physical benefits as conventional long duration endurance training despite taking much less time (and amazingly, actually doing less exercise!) However, their previous work used a relatively extreme set-up that involved “all out” pedaling on a specialized laboratory bicycle. The new study used a standard stationary bicycle and a workload which was still above most people’s comfort zone -about 95% of maximal heart rate — but only about half of what can be achieved when people sprint at an all-out pace.

This less extreme HIT method may work well for people (the older, less fit, and slightly overweight among us) whose doctors might have worries about them exercising “all-out.” We have known for years that repeated moderate long-term exercise tunes up fuel and oxygen delivery to muscles and aids the removal of waste products. Exercise also improves the way muscles use the oxygen to burn the fuel in mitochondria, the microscopic power station of cells. Running or cycling for hours a week widens the network of vessels supplying muscle cells and also boosts the numbers of mitochondria in them so that a person can carry out activities of daily living more effectively and without strain, and crucially with less risk of a heart attack, stroke or diabetes.

But the traditional approach to exercise is time consuming. Martin Gibala and his team have shown that the same results can be obtained in far less time with brief spurts of higher-intensity exercise. To achieve the study’s equivalent results by endurance training you’d need to complete over 10 hours of continuous moderate bicycling exercise over a two-week period. The “secret” to why HIT is so effective is unclear. However, the study by Gibala and co-workers also provides insight into the molecular signals that regulate muscle adaptation to interval training. It appears that HIT stimulates many of the same cellular pathways that are responsible for the beneficial effects we associate with endurance training. The upside of doing more exercise is well-known, but a big question for most people thinking of getting fit is: “How much time out of my busy life do I need to spend to get the perks?”

Martin Gibala says “no time to exercise” is not an excuse now that HIT can be tailored for the average adult. “While still a demanding form of training,” Gibala adds, “the exercise protocol we used should be possible to do by the general public and you don’t need more than an average exercise bike.” As the evidence for HIT continues to grow, a new frontier in the fitness field emerges.

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High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: review & meta-analysis

1School of Human Movement Studies, The University of Queensland, St Lucia, Brisbane, Queensland, Australia

2Department of Circulation and Medical Imaging, Faculty of Medicine, Center of Exercise Medicine at Norwegian University of Science & Technology Norway.

Published Online First 21 October 2013

Abstract

Background/Aim Cardiorespiratory fitness (CRF) is a strong determinant of morbidity and mortality. In athletes and the general population, it is established that high-intensity interval training (HIIT) is superior to moderate-intensity continuous training (MICT) in improving CRF. This is a systematic review and meta-analysis to quantify the efficacy and safety of HIIT compared to MICT in individuals with chronic cardiometabolic lifestyle diseases.

Methods The included studies were required to have a population sample of chronic disease, where poor lifestyle is considered as a main contributor to the disease. The procedural quality of the studies was assessed by use of a modified Physiotherapy Evidence Base Database (PEDro) scale. A meta-analysis compared the mean difference (MD) of preintervention versus postintervention CRF (VO2peak) between HIIT and MICT.

Results 10 studies with 273 patients were included in the meta-analysis. Participants had coronary artery disease, heart failure, hypertension, metabolic syndrome and obesity. There was a significantly higher increase in the VO2 peak after HIIT compared to MICT, equivalent to 9.1%.

Conclusions HIIT significantly increases Cardiorespiratory fitness (CRF) by almost double that of MICT (moderate-intensity continuous training) in patients with lifestyle-induced chronic diseases.

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