I’m a fan of exercise, but the way it’s commonly prescribed for weight loss (regular, aerobic activity such as running, cycling or rowing) does not actually appear to be very effective for here. Though, of course, it might be good for other things such as protection from chronic diseases such as heart disease and type 2 diabetes, as well as perhaps being good for mood and self-esteem. Of course another thing exercise is good for is that it can help people be fitter and go faster.
In recent times I’ve become quite interested in a form of exercise that is often termed ‘high intensity intermittent exercise’ (HIIE) or ‘high intensity intermittent training’ (HIIT) (I’ll use ‘HIIE’ from her on). This form of exercise basically involved periods of intense, short-duration activity (such as sprinting), interspersed with periods of rest or low-level activity (such as slow jogging). There’s growing evidence that HIIE can, compared to ‘steady state exercise’ (such as running at a continuous pace) boost fitness and even fat loss, and do it in a time-efficient manner too.
In one study, women engaged in either HIIE or steady state cycling for 15 weeks. The steady state exercise involved 40 minutes of continuous exercise. In this study, HIIE came in the form of 8-second cycle sprints interspersed with 12-second rest periods, for a total of 20 minutes. Exercise sessions were performed 3 times a week [1].
Over the course of the study, individuals engaging in HIIE lost a total of 2.5 kg of fat. In contrast, the individuals who engaged in steady state exercise lost no weight at all.
Another interesting study included in the review compared HIIE with steady state exercise in subjects diagnosed with metabolic syndrome [2]. Half the group performed 4 minutes of exercise at 90 per cent maximum capacity followed by 3 minutes of ‘recovery’ exercise for a total of four cycles. The remaining individuals exercised continually at 70 per cent maximum capacity for a similar length of time.
Fitness increased in both groups, but rose by about twice as much in the HIIE group compared to the steady state exercisers. Also, HIIE was significantly more effective in reversing signs of metabolic syndrome.
I was interested to see a recent study regarding HIIE has been published [3]. In this study, 18 trained runner were randomized to one of two training regimes over 7 weeks.
1. regular, steady-state-based training
2. high-intensity intermittent exercise
Each session was made up of the following components:
1 km of warm-up
5 mins of ‘interval training’ where each minute is made up of running for 30 seconds at low intensity, 20 seconds at moderate intensity and 10 seconds at near maximal intensity
2 minutes of rest
This 7 minute block was repeated 3-4 times
The total exercise time for the HIIE runners was reduced by more than half compared to the steady state runners.
At the start and end of the study, all the study participants ran 1500 and 5000 metres time trials.
The steady state runners did not see an improvement in their times over 7 weeks. However, the HIIE saw reductions of 21 and 48 seconds respectively. They also enjoyed reductions in cholesterol (for what that’s worth) and blood pressure which were not seen in the other group.
This study adds to the growing body of evidence which shows that HIIE can be a relatively time-efficient way to derive health and fitness benefits from exercise. As with everything, it’s not for everyone. However, for individuals already used to exercise, employing some HIIE in their regime can often pay significant dividends in less time than traditional training.
References:
1. Trapp EG, et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International Journal of Obesity 2008;32(4):684–691
2. Tjønna AE, et al. Aerobic interval training versus continuous moderate exercise as a treatment for the metabolic syndrome: a pilot study. Circulation 2008;118(4) 346–354
3. Petursson-Gunnarson T, et al. The 10-20-30 training concept improves performance and health profile in moderately trained runners. Journal of Applied Physiology, 3 May 2012
I’m curious to know what kind of intensity the “steady state” training was done at. I’ve been reading up on MAF (Maximum Aerobic Function) training, as espoused by Phil Maffetone and it’s been quite enlightening.
Most people doing “cardio” work, exercise at an intensity that is actually quite anaerobic, thus needing glucose. Building a good aerobic base by exercising longer, and at a lower intensity is supposed to be better for fat burning, and for building endurance.
Dr Mark Cucuzella has some interesting information about it at http://www.freedomsrun.org/Training/TrainingAerobic.aspx
I suspect that either real aerobic exercise, or HIIE will give better results than what Mark Sisson calls “chronic cardio”. I know that when I attended “aerobics” classes that I ended the classes with some serious oxygen debt, implying to me that it was much more anaerobic than aerobic.
When discussing reference 2 DrBriffa mentions 70% intensity. This could be VO2max or heart rate. I couldn’t find the reference 3 online so I’m not sure. There is a formula courtesy of David Swain that equates HR 70% with VO2 max of 52% and a VO2max of 70% with a heart rate of 82%. Either way this exercise shouldn’t feel ridiculously easy or hard.
From long experience both coaching endurance athletes including myself I’d say the following:
The long steady Phil Maffetone approach only works for people training upwards of 10 hours a week with individual sessions that last over 2 hours. Some people respond to this type of training more quickly than others, but my experience is that people training over 15 hours a week can use it quite effectively to improve fitness. The problem is that training at such low intensity does not always condition the muscles, including the heart and lungs for racing at much higher intensity.
The medium intensity approach is generally overused. It is the standard zone for athletes who tend to get stuck at one level and cannot produce any peak performance during the season.
The high intensity training is a key to developing speed. Nobody at the top level ignores these type of sessions, but it is easy to overdo it. Novices need to be careful they don’t strain muscles if they haven’t done fast sprinting / static bike exercise before. More serious athletes need to be conservative with the amount they do. Overdoing it rapidly leads to generalised fatigue, which needs to be handled carefully. Sometimes you can push some more the next day, sometimes you need a more prolonged time of lower intensity exercise.
When starting from a low base I tend to use more moderate intensity exercise. At this stage I find my race performances are normally pretty poor. As I get fitter I do more high intensity work, this leads to fatigue and I often find myself doing more low intensity exercise (slower than when I started back from a low base) between high intensity sessions. Medium intensity definitely falls during this phase. Despite these slow sessions when you are tired, I normally race well after a day or twos rest during these phases.
Interval training is here to stay. The evidence is mounting well in its favor. You are also able to work out in less time than steady state workouts which is a plus.
I love HIIT training – when I’m jogging, I will always slowly jog between 3 lamp-posts, and sprint through one. Makes me feel great and feel much fitter, faster.
I’ve always been told HIIT is training smart, not hard, and great for when people don’t have as much time to exercise.
Isn’t this similar to what, as children, we called Scouts’ pace? I wonder whether the
Boy Scouts (or Girl Guides) still do it.
Fiona, not really. Scout’s pace (as I recall) was alternating jogging and walking. High Intensity Intervals are sprints alternated with resting.
The June issue of the Mayo Clinic Proceedings includes a review of how excessive endurance exercise is thought to cause damage to the heart.
http://www.cbc.ca/news/health/story/2012/06/01/marathon-endurance-heart.html
Dr. James O’Keefe, Clinical Cardiolgist from Saint Luke’s Mid America Heart Institute in Kansas City, Missouri, describes the risks and benefits of extreme endurance exercise, emphasizing the Importance of moderation.
http://www.youtube.com/watch?v=jp_zviTtIQk
I’m still surprised to find this sort of thing being researched, as if we didn’t already know that HIIT is just as beneficial for athletes as it is for regular folks, if for different reasons.
I remember reading an article by Frank Horwill in Peak Performance about 12 years ago where he was lamenting the lack of progress in British runners due to their inhibition to take up more modern running training practices. What practices? Sprint training, HIIT and one other I now can’t remember.
This was over 10 years ago and he thought they were already too late in changing….
I’m also reminded of the study my tutor did with British 800m runners; he got them to do sprint training instead of some of their endurance training and they improved their times. When the study had finished he asked their coaches if they would take on board the improved performances and incorporate them into their programmes. The answer? No, they didn’t see how they would fit into a ‘proper’ running programme!
Makes me wonder….
Cheers
George