Monday, 9 February 2015

Interval Training: Stop with the Tabatas and do some Gibalas!

   Sprinting would obviously have been a necessary requirement for Paleolithic hunter-gatherers, both for the procurement of food and to avoid becoming food! Those who want to argue against that statement with the “persistence hunting” position, I will address that in a future post. Regardless, let’s fast forward to modern day and address a topic pertinent to my initial statement. To say that “Tabatas” have become an extremely popular interval training protocol in the fitness industry would be an understatement. When I wrote a position paper1 back in 2008 on the benefits of sprint interval training, the research conducted by Izumi Tabata et al. was obviously referenced as it added to the body of evidence that supports the benefits of high-intensity intermittent (interval) training (HIIT). However, the interpretation of this protocol in the fitness industry has often been misunderstood, and even when done correctly, I would argue that, for most individuals, it is not the most effective approach to interval training. After all, the protocol tested was simply one that was first introduced by a head coach of the Japanese National Speed Skating Team, Kouichi Irisawa; a protocol one would assume worked well for certain athletes based upon the duration of their events. Further, most good coaches use training methods that are often experimentations that change with time, as more successful protocols take shape. Along these same lines, I believe most people could improve their investment of time by not using the Tabata protocol for their interval training; but rather, use a different approach.
For the uninformed, in 1996, Tabata et al. published the findings of a study comparing moderate-intensity endurance training (MIET – 70% VO2 max for 60 minutes, 5 days per week) with HIIT (170% VO2 max for 20 seconds x 7-8 with 10 seconds recovery, 5 days per week) on a cycle ergometer.2 The study found that HIIT improved maximal oxygen uptake slightly more than MIET; but, also improved the anaerobic capacity by 28% while the MIET had no effect on the anaerobic capacity. So, essentially, a “two for one” in terms of improving metabolic capacities for the HIIT protocol.
While the results of the study were important for the comparison of MIET to HIIT, other interval training protocols have demonstrated similar and; in some cases, even greater benefits with a decreased investment of time.3, 4, 5, 6 These latter studies support what I have witnessed clinically over nearly 20 years, which is, that intensity, not duration, is the key ingredient for beneficial physiological change. The intensity of the HIIT protocol examined in the Tabata study was 170% VO2 max, which, while correctly being labeled supramaximal (above 100% VO2 max) and certainly “high-intensity,” is nowhere near a maximal sprint effort given that humans are capable of intensities around 250%. The power output sustained for a maximal effort for the duration of the exercise time of the Tabata HIIT protocol (140 seconds to 160 seconds), is very different to the power output sustained for a maximal effort for an “all-out” sprint lasting, say, 30 seconds. If 170% VO2 max was all one had to escape a predator in primitive times (or today for that matter), it is pretty much a guarantee that you are going to be out of the gene pool in short order! 100% VO2 max represents the power output attained when one reaches maximal oxygen consumption during a graded exercise stress test. Any human starting out at that equivalent intensity would not find it anywhere near a maximal effort for a short “all-out” sprint.
When sprinting “all-out,” most individuals are going to start slowing down within seconds; but, could probably still hold a decent percentage of their maximum power output for anywhere between 20-60 seconds, depending on their level of conditioning, and, in particular, their ability to handle the lactic acid production associated with supramaximal exercise. Considering the short duration of supramaximal activity, it generates a relatively large volume of excess post-exercise oxygen consumption (EPOC), partly due to the lactic acid production. Research has shown a significantly larger EPOC is generated for a 45 second “all-out” sprint compared to a 30 second “all-out” sprint, and a significantly larger EPOC is generated for a 60 second “all-out” sprint compared to a 45 second “all-out” sprint.7 However, a 90-second “all-out” sprint did not generate a larger EPOC than a 60 second “all-out” sprint. The reason for this is that lactic acid production typically reaches its peak at around 60 seconds of supramaximal exercise, which, in turn, inhibits muscular contraction and thereby decreases the production of further large quantities of lactic acid.  Anyone can easily experience this for him or herself. There simply is not a human on the planet that can maintain close to maximal power output without a precipitous drop-off at around 60 seconds. If you find otherwise, immediately contact your country’s Olympic Committee as I can assure you that you will be in high demand! So, 60 seconds is essentially a maximal and optimal duration to engage in supramaximal activity. Perhaps selective pressure with respect to our ancestral survival played a part in this physiological reality.
Now, back to the Tabata protocol. There are two ways in which individuals in the fitness community are misinterpreting this methodology. First, and perhaps somewhat ridiculously, are those individuals and classes that label their work-outs as “Tabatas” because they simply exercise for 20 seconds (at relatively low intensities), rest for 10 seconds, and then repeat the same for seven to eight intervals, and then, in some cases, even repeat again for an hour long workout. Anyone engaging in this approach is as far away from supramaximal interval training as one can get. The second misinterpretation comes from those that are completing the seven to eight 20 second intervals as “all-out” efforts.  With this approach, based upon the previous discussion about 60 seconds being an maximal duration for “all-out” exercise, any intervals past the first three 20 second sprints are essentially a waste of time. The only way someone can complete seven to eight 20-second intervals with only a 10-second recovery is to back down from an “all-out” sprint, to an intensity similar to that tested in the Tabata study. Doing this certainly has its merits for athletic endeavors that last for 140 seconds to 160 seconds; however, for the average individual and most athletes, I would argue that the protocol researched by the group headed by Martin Gibala from the Department of Kinesiology at McMaster University in Hamilton, Ontario, Canada, is a much more effective approach to interval training.
This protocol, as first described by Burgomaster et al.,3 involves completing “all-out” 30-second sprints (also on a cycle ergometer) with a 4 minute recovery between exercise bouts. The number of sprints increased from 4 during the first two sessions, to 5 in the third and fourth sessions, and 6 in the last two sessions. The total time commitment was 17–26 minutes per session, involving only 2–3 minutes of sprint exercise. Exercise sessions were completed every two to three days such that 16 minutes of exercise was completed in a two-week time period.  The results of this protocol showed a doubling of the participants’ endurance capacity! So these benefits occurred over a two-week period using just 16 minutes of sprinting. Further studies using this same protocol have been shown to substantially improve insulin action in young sedentary subjects, a much-needed outcome in this world full of metabolic syndrome.4 This demonstrates that quality not quantity causes physiological change for the better and, in many cases, the Tabata protocol in the fitness industry has become a methodology that has moved away from quality toward quantity. Further research has now shown that intense bouts as short as 6-20 seconds can have a tremendous benefit on physiological health, emphasizing, again, that intensity, not duration, is the key element to beneficial change.5,6 I have also found clinically, that these very short bouts of intense activity are better adhered to while still providing tremendous improvements in health and performance.
Moreover, I found a common objection to this methodology is that unfit and elderly individuals should not engage in this type of supramaximal activity due to the inherent dangers of engaging in such intense activity. With extensive experience in this field, I have never had a situation where an unfit individual or an elderly individual has had a problem with engaging in this kind of supramaximal activity. In fact, I would argue that it is beneficial to engage in this type of exercise in a controlled environment; rather than leave it to the reality of life where external pressures may demand an effort above which one is physiologically not trained to handle.  Interestingly, an increased QT dispersion (QTd) – a marker of myocardial electrical instability that predicts ventricular arrhythmias and sudden cardiac death – has been shown to be decreased with short-term supramaximal exercise.8 This supports the notion that short-term supramaximal exercise is an appropriate approach for anyone to improving one’s physiological health.
In closing, unless you have an athletic event lasting between 140 seconds to 160 seconds, skip the Tabatas and engage in Gibalas or some other shorter interval training protocol that produces better results with a smaller investment of time.  And don’t overdo the quantity of “all-out” sprints – eight to twelve minutes per week is sufficient to reap the benefits without the risks associated with overtraining.

Source Dr. Mark J. Smith

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