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
