Around 31% of the world’s adult population does not get sufficient exercise, and approximately 3.2 million deaths worldwide each year could be prevented with exercise. The prevalence of foods high in sugar and fat, coupled with a busy schedule means it's easier than ever for people to forgo exercising. But even a couple minutes of exercise each day can do wonders and protect your health. Moreover, if you do it right, you could garner the same health benefits as an hour-long cardio session.
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What is HIIT
In this respect, high intensity interval training (HIIT) has been gathering a lot of steam among fitness enthusiasts. HIIT pairs quick bouts of high-energy exercise with low-effort rest intervals. Basically, high intensity means anywhere from 80% to maximum capacity for 30 seconds. For example, a dead sprint would be considered maximum capacity.
Traditionally, long continuous endurance training (ET), exercising for around an hour, has been seen as the most effective way to achieve health benefits. The scientific literature, however, suggests that HIIT could be just as good as ET and if the two are paired it could provide a lot of progress. It's no wonder that some of the best athletes in the world use it. Actually, they've been using it for years. As early as 1912, the Finnish Olympic long-distance runner Hannes Kolehmainen was using interval training in his workouts.
HIIT Health Benefits
Helgerud et al. showed in 2007 showed that 4 repetitions of 4-minute runs at 90%–95% of heart rate maximum (HRmax) followed by 3 minutes of active recovery at 70% HRmax performed 3 days per week for 8 weeks resulted in a 10% greater improvement in stroke volume than did long, slow distance training 3 days per week for 8 weeks.
VO2max is considered the body’s upper limit for consuming, distributing and using oxygen for energy production. Daussin et al. (2008) measured VO2max responses among men and women who participated in an 8-week HIIT program and a continuous cardiovascular training program. VO2max increases were higher in the HIIT program (15%) than they were in the continuous training program (9%).
Exercising increases the mitochondria (a cell's battery; the biological "power house" as often labeled) density. As this density increases, so does the available energy allowing, for instance, a runner to run longer and at higher intensity. For a long time, it was thought a significant increase can only be achieved though endurance training. Burgomaster et al. (2008) showed, however, that a HIIT program consisting of four to six 30-second maximal cycling sprints (followed by 4.5-minute recovery bouts) 3 days per week provided similar increases in levels of oxidative enzymes as those who performed 40–60 minutes of steady cycling at 65% VO2max 5 days per week. More mitochondrial oxidative enzymes means fat and carbohydrates are broken down more effectively as fuel.
A well 'oiled' vascular system is essential for healthy insulin response, blood pressure regulation, prevention of atherosclerosis, proper cardiac performance and the delivery of oxygen and other vital substances around the body. One of the main factors that contribute to vasodilation is nitric oxide (NO). Cocks et al. (2013) found that six weeks of SIT led to a 36% increase in endothelial nitric oxide synthase (eNOS) while ET over the same time period only led to a 16% increase.
Insulin resistance plays a large role in the formation of type 2 diabetes, and is also associated with other problems such as obesity and coronary heart disease. Unsurprisingly, insulin resistance increases following periods of physical inactivity. Whyte et al. (2010) invited 10 overweight/ obese sedentary men to participate in a study where they had to perform six sessions of 4-6 intervals of 30 second Wingate springs. After two weeks of this type of HIIT intervention, insulin sensitivity greatly improved.
Why HIIT can be just as good as hours of endurance training
Researchers at Stockholm’s Karolinska Institutet published a paper this week detailing the cellular mechanisms involved in the positive benefits of HIIT. Apparently, HIIT triggers the triggers the breakdown of calcium channels as a result of enhanced free radical production.
Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules.These can cause damage when they react with important cellular components such as DNA, or the cell membrane, causing the cells to function poorly or even terminate them. To prevent free radical damage the body has a defense system of antioxidants.
In this particular case, the free radicals are a good thing. Our muscles aren't static and in order to improve protection against stress, then they need some stress to respond to. A shower or short-burst of free radicals, thus, is essentially beneficial. In fact, strong antioxidants actually prevent some of the muscle adaptation to training. Diseases resulting from free radicals occur during long-term oxidation of the cells.
"Our study shows that antioxidants remove the effect on the calcium channels, which might explain why they can weaken muscular response to endurance training and they also show that the calcium channels aren’t affected by the three minutes of high-intensity interval exercise in elite endurance athletes, who have built up more effective antioxidative systems," said Hakan Westerblad, a professor of physiology and pharmacology.
The paper concludes:
"Elite endurance athletes have long appreciated the role of high-intensity interval exercise as part of a comprehensive training program. Recent evidence suggests that V in young healthy persons of average fitness V intense interval exercise is a time-efficient strategy to stimulate a number of skeletal muscle adaptations that are comparable to traditional endurance training. However, fundamental questions remain regarding the minimum volume of exercise necessary to improve physiological well-being in various populations, the effectiveness of alternative (less extreme) interval-training strategies, and the precise nature and magnitude of adaptations that can be elicited and maintained over the long-term. A comprehensive evaluation of the physiological adaptations induced by different interval-training strategies in a wide range of populations will permit evidence-based recommendations that may provide an alternative to current exercise prescriptions for time-pressed individuals."
Some beginner HIIT workouts
Walking: Repeat 10 times (30 minute workout) total
- Work Interval: 2 minutes, Walk at 90% effort / 5.0-5.5 mph on the treadmill
- Rest Interval: 1 minute, Walk at 60% effort / 4.0-4.5 mph on the treadmill
Running: Repeat as many times as possible in 10 minutes
- Work Interval: 100m sprint
- Rest Interval: 200m easy jog
Swimming: Repeat 10 times (1000m total)
- Work Interval: 50m freestyle sprint
- Rest Interval: 50m easy breast stroke
Cycling: Repeat 15 times (30 minutes total)
- Work Interval: 90 seconds max effort pedaling
- Rest Interval: 30 seconds easy pedaling
Rowing: Repeat 8 times (4000m row) total
- Work Interval: 500m, 90% effort
- Rest Interval: 500m, 60% effort
Bodyweight: Repeat 5 times
- Work Interval: 10 Burpees + 10 Jump Squats + 10 Push Ups
- Rest Interval: 30 seconds stretching
Weightlifting: Repeat 5 times
- Work Interval: 10 Back Squats + 10 Barbell Rows
- Rest Interval: 30 seconds plank