Exercise Workouts / Category / Emile Du Toit / May 5th 2014
I often find that with these sorts of articles when one compares one exercise modality (or indeed substance) with another it soon becomes a competition, where one option is allegedly horrific and the other amazing and without any potential problems.
Basically, ‘scientific’ studies sometimes become marketing campaigns where integrity is lost and all you end up with is propaganda!
So let me start out by saying that I do not have an agenda that I am trying to force-feed you. Over the years I have been involved in aerobic exercise, strength training, traditional interval training and (much more recently) short-duration high intensity interval training. They all have merit, and if you find something that really works for you that isn’t directly dangerous then it is probably doing you a lot more good than harm.
Don’t knock endurance training; it has helped millions of people worldwide!
Endurance training, although much lengthier, feels a whole lot better than HIIT. You get to cruise along at moderate HR max and if the duration is long enough your body releases natural opioids that make you feel, well … rather great really! With short duration HIIT you just feel bloody tired during as well as afterwards!
Nevertheless, this is a comparison of HIIT with endurance training, so let’s get to it.
High intensity interval training gives a natural boost to human growth hormone (HGH) production, which you don’t get from normal sustained effort endurance exercise. This hormone has been shown to clearly demonstrated to significantly increase muscle growth, boost fat loss and improve insulin sensitivity.
One study showed that 3 minutes of short duration high intensity interval training just once a week improved insulin sensitivity an average of 24%! 1. This means that HIIT is excellent at slowing or even halting the onset of diabetes type 2.
Okay so biology 101 tells us – or should if the course is worth its salt – that there are three types of muscle fibres. We have slow twitch, fast twitch and super-fast twitch muscles.
Traditional endurance aerobic exercise only utilises the slow-twitch muscles and they only involve an aerobic metabolic process (i.e. oxygen is required). In contrast HIIT utilises slow twitch, fast twitch and super-fast twitch muscles. This utilises both aerobic metabolic processes as well as anaerobic metabolic processes (where no oxygen is utilised).
In order to optimally protect the heart, both aerobic and anaerobic metabolic processes are required.
Extended extreme cardio actually sets off inflammatory mechanisms that damage your heart. So while your heart is strengthened by working hard indeed, it is not designed to do this continually and definitely not for an hour or more at a time!
Research tracking 52 600 runners for 3 decades demonstrated that runners lived longer than non-runners. However, those running more than 35 km a week lost that advantage. The best survival rates occurred with athletes who ran at a slow to average pace for a total of 1 to 2.5 hours per week, divided amongst 2 – 3 runs.
There is near unanimous agreement between cardiologists that endurance training significantly increases the risk of atrial fibrillation, an arrhythmia that is estimated to be the cause of one third of all strokes
This is one of the reasons why long distance athletes such as marathon runners sometimes just drop dead. In contras high intensity interval training works in synchronicity with the body’s natural mechanics. There is an ever growing body of research demonstrating that the ideal exercise form for your heart is short bursts of extremely high intensity.3.
There is a wealth of research showing that HIIT increases skeletal muscle oxidative capacity significantly better than endurance exercise does.
It does appear that HIIT helps people to lose more weight at a much quicker rate. 2. 17.
One particular University of New South Wales study examined subjects who spent 20 minutes mixing sprints with jogging, over a 15 week period. These subjects lost 3 times the amount of leg and butt fat than the control group who would jog for 40 minutes.
Another Australian study examined subjects who spent 3 20-minute stints of interval training on a bike every week, for 12 weeks. They concluded that the amount of fat that these subjects lost on their hour per week of interval training was the equivalent of spending 5-7 hours a week jogging!
When compared to endurance exercise on a matched-work basis – basically where the energy expenditure is the same - short duration HIIT outperformed the endurance training on several measures, including the following: 4. 5. 8. 13.
HIIT involves much shorter exercise duration than moderate intensity endurance exercise.
Obviously these figures vary depending on the nature of both training regimes, but one study found short duration HIIT to utilise 10% of the exertion time and 25% of total training time of endurance training.
This is vital as the number one reason given for not exercising is that people don’t have the time.
Research shows that HIIT is (again on average) regarded to be more interesting than standard, constant effort aerobic routines. This too is important as many exercisers and gym goers hang in there for several months and then drop out of exercising altogether, before beginning the cycle again!
To provide a context to how important this is, only 20.6% of adult Americans met the 2011 Physical Activity Guidelines for both aerobic and muscle-strengthening physical activity.
HIIT has also been shown by Dr Tabata to burn an additional 150 calories in the 12 hours after exercise, due to the extreme post-workout oxygen consumption. It increases the resting metabolic rate for the following 24 hours due to excess post-exercise oxygen consumption, which is significantly more than with endurance training. 9. 12. 14.
So you continue to burn a lot more calories even when not training!
I scanned a fair number of responses to HIIT to look for any constructive negative feedback. Actually, I could only find two that appeared evidence based. The one came from the proponents of HIIT themselves, who have pointed out that some short-duration HIIT training regimes are not suitable for some cardio and chronic illness patients. There are modified HIIT programs designed for these population groups. The second is that many of the HIIT research studies are relatively short-term still, and longer term studies need to be conducted. The longest HIIT study that I have perused was a 9 month one, with most being more like 3 months in length, so longer studies are necessary.
As shown above, I believe that short-duration HIIT shades endurance training in terms of efficiently increasing fitness and decreasing risk of a plethora of chronic illnesses.
However, different people respond to exercises in different ways, and I do not doubt that for unique psychological or physiological reasons some people will prefer to embrace endurance training. I strongly suspect that even for these people though, combining some HIIT into their training routine will be beneficial.
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