“This has the potential to change the way we think about
keeping fit. We thought there would be benefits but we did not expect them
this obvious. It shows how effective short intense exercise can be.”
~ Professor Martin J. Gibala (London Telegraph, June 5,
slowly the rest of world figures this out.” Laszlo Bencze
Sprints Build Endurance!
Tabata-type Training Takes Center Stage
Minutes Potent as Two Hou
Intensity Trumps Volume
My friend Richard Winett, PhD, publisher of Master
Trainer, was one of the first in this country--perhaps the first--to write about Dr. Izume Tabata’s groundbreaking research published
in 1996, on short, intense intervals. Dr. Tabata and his colleagues at the
National Institute of Health & Nutrition, Tokyo, Japan,
reported: "[Six to 8 very hard 20 second intervals
with 10 second
rest periods] may be one of the best possible training protocols…” Dr.
Tabata told Dick Winett in a personal communication: "The rate of increase in VO2max [14% in only 6 weeks] is one of the highest ever reported in
exercise science." What’s more, anaerobic capacity increased by a
Several of the earliest articles on this website were about
high intensity intervals for fitness and fat loss; articles 10 and 11 in our
Aerobic Exercise category discuss Dr. Tabata’s research.
Because of my interest in high-intensity
aerobics (I first wrote about it in Ripped 3), quite a number of
people emailed about the recent research on sprint interval training done by
Kirsten Burgomaster and colleagues at McMaster University, Hamilton, Ontario,
Canada, and published in the Journal of Applied Physiology (June
In that study, sixteen active but untrained
students, average age 22, were divided into two groups: eight who
performed two weeks of sprint intervals, and eight controls who were tested
before and after, but did no training.
The test group did four to seven “all-out” 30-second
sprints on a bicycle ergometer with four-minute rest periods, six times over two
Tabata’s subjects did intervals five days a week for six weeks; the rest
periods were much shorter, of course. We’ll discuss the differences in the two
The muscles of
the trained group showed substantial aerobic adaptation: 38% increase in
citrate synthase, a mitochondrial enzyme that indicates the power to use oxygen, and
a 26% increase in glycogen (muscle sugar) content. Interestingly, there was no
change in peak oxygen uptake (VO2max) or anaerobic work capacity.
“Most strikingly,” the researchers wrote, “cycle
endurance capacity increased by 100% after [sprint interval training].” The
time to fatigue cycling at about 80% of VO2max increased on average from 26
minutes to 51 minutes!
The control group showed no change in any of the test
“To our knowledge, this is the first study to show that
sprint training dramatically improves endurance capacity during a fixed workload
test in which the majority of cellular energy is derived from aerobic
metabolism,” the researchers reported. Impressively, the short
period of very intense exercise produced improvements “comparable to or higher
than previously reported aerobic-based training studies of similar duration.”
In other words, about two minutes of very intense exercise (15 minutes over 2
weeks) produced the same or better results than previously shown after two hours
a day at about 65% of VO2max, or 20 hours over two weeks.
Intervals for the Masses
Although in some ways less impressive the Dr. Tabata’s
results (more later), the new study has created quite a stir, especially among
health professionals eagerly looking for ways to motivate people to exercise.
Martin J. Gibala, an associate professor in the Department
of Kinesiology at McMaster University and lead spokesman for the new study,
has been quoted widely in this country, Canada and in the UK.
“The whole excuse that ‘I don’t have enough time to
exercise’ is directly challenged by these findings,” Gibala told the London
Telegraph. “This has the potential to change the way we think about
keeping fit. We have shown that a person can get the same benefits in fitness
and health in a much shorter period if they are willing to endure the discomfort
of high-intensity activity.”
“This type of training is very demanding and requires a
high level of motivation; however less frequent, high intensity exercise can
indeed lead to improvements in health and fitness,” Gibala told CNN.
“We thought the findings were startling,” Gibala told CTV,
Canada, “because it suggests the overall volume of exercise people need to
do is lower than what’s recommended.” He added, “We think there might be a
public health message that you can perform intense exercise, but less volume,
and obtain similar benefits.”
The Journal of Applied Physiology found the new
study noteworthy enough to merit a thought provoking “Invited Editorial” in
the same issue by Edward F. Coyle, Department of Kinesiology and Health
Education, University of Texas at Austin.
Not only is the study a “documented first,”
Coyle writes, it “serves as a dramatic reminder of the potency” of intense
exercise to improve performance, with “implications for improving health.”
It shows that sprints are “very time efficient, with much bang for the
Challenge to Conventional Wisdom
It seems logical, says Coyle, that “aerobic endurance
performance is only enhanced by aerobic endurance training, but it has been
proven wrong in the realm of athletics as well as muscle biochemistry.” In
short, prolonged low intensity exercise is not necessarily the best way to
build endurance. Long slow running or biking may be a waste of time for people
who want to become fit and healthy but have no plans to run a marathon or
compete in high-level bicycle racing.
Coyle observes that middle-distance runners typically
include sprint intervals in their training to improve aerobic endurance.
“Indeed,” he writes, “it is likely that if an experienced runner or
bicyclist had only 2 weeks and very limited time to prepare for a race of
[about] 30-minutes duration, that sprint interval training would become a
mainstay of their preparation.” Roger Bannister’s preparation to run the
first 4-minutes mile is a classic case in point; see article 136 in our Aerobic
Coyle points to the recent popularity on “spinning” as
an indication that the idea may be catching on in the general fitness
population. “From the perspective of muscle biochemistry,” he adds, “it
has long been recognized that 6-8 weeks of sprint interval training increases
aerobic enzyme activity in muscle [citing several studies].”
Regarding the health implications, Coyle adds: “The large
increase in citrate synthase activity in muscle implies that a host of
adaptations typical of aerobic endurance training have been initiated, such as
improved insulin action, improved lipoprotein lipase activity, and greater
clearance of plasma triglycerides [citing studies].”
Referencing a research paper about the evolutionary
underpinning of modern chronic diseases, Coyle suggests that sprint interval
training might be an efficient way to keep our sedentary population from
crossing “a biological threshold, beyond which chronic health conditions
develop.” (See “Grow Or Decay, Your Choice,” # 146, Health and Fitness
Energizing the Fibers
What accounts for the surprising effectiveness of very hard
30-second sprints in improving endurance capacity? It obviously works, but why?
What’s the precise mechanism? The researchers offered a smorgasbord of
possible mechanisms, but I found the explanation offered in the
editorial more satisfying and quite logical.
“We can only
speculate,” the researchers state, “but it is plausible that a
training-induced increase in mitochondrial potential, as measured by citrate
synthase maximal activity” is responsible for the improvement. Being good
scientists, however, they go on to muddy the water, perhaps unnecessarily: “However,
the precise mechanisms that regulate endurance performance are multifactorial
and extremely complicated, and the data from other studies suggest that sprint
training can stimulate a range of adaptations that might facilitate performance
aside from changes in mitochondrial potential.” They then proceed to give a
long list of possibilities that only an exercise physiologist would appreciate.
The editorial, on the other hand, goes for the jugular. Coyle says
that both sprint interval training and prolonged sub-maximal aerobic exercise
increase mitochondrial potential, but reminds us that the muscle fibers affected
are different. The specific fibers affected probably explains why
very brief sprint training proved to be as effective [or more effective] for
improving endurance as much longer and less intense aerobic training, according
to Coyle. “All-out sprint training especially stresses recruitment and
adaptation of fast twitch muscle fibers that are remarkably and equally
responsive as slow twitch muscle fibers in their ability to increase
mitochondrial enzyme activity,” Coyle explains. “In fact, the low-intensity
aerobic exercise that is typically prescribed for endurance training or health
is not very effective at increasing aerobic activity in [fast twitch] muscle
fibers, which comprise approximately one-half of the fibers within the muscles
of most people,” he continues. “Thus low-intensity aerobic training is not a
very effective or efficient method for maximizing aerobic adaptation in skeletal
muscle because it generally does not recruit
[fast twitch] fibers.”
In other words, sprint interval training increases the
endurance capacity in all muscle fibers, fast and slow, while long slow training
leaves half of the fibers unused and untrained. Makes perfect sense, doesn’t
it? It’s like pulling the wagon with one horse, when two would get you a lot
farther down the road. (See Ripped 2 for an explanation of the
“all-or-none” law of muscle fiber recruitment, and The Lean Advantage
(first volume) on the order in which muscle fibers, slow and fast, are
A Price to Pay
There is no free lunch, of course. High-intensity intervals
are hard. The editorial also addressed
this issue. “[Repeated all-out sprints] cause a feeling of severe fatigue
lasting for at least 10-20 minutes,” Edward Coyle writes. “That is the price
for its effectiveness and remarkable time efficiency. It remains to be
determined which population, depending on age, health status, and psychology,
are most likely to adhere and benefit from sprint interval training.” The
possibility of injury is also a factor to be considered. “Chance for impact
injury during stationary cycling or swimming seems low and might be compared
with sprint running,” Coyle suggests.
Recognizing that adherence and motivation would be an
issue, the London Telegraph asked three “quite fit” employees
of the Reebok Sports Club in Canary Wharf, London, to evaluate sprint intervals.
As might be expected, reviews were mixed.
One eager beaver, 35, rode for 10 minutes in 60-second
sprints. “It felt like I had just done an hour’s run,” he reported. “It
was more than I was used to but I feel more exhilarated because it was so
“To be honest, it was not much fun and unless I was
really pressed for time I would not change my exercise regime,” he added.
Another fellow, 23, tried the two minutes of cycling in
30-second super-bursts and found that he was exhausted. “It was torture,
really, but I was amazed at how short a time it took me to tire myself out
completely,” he related. “I didn’t enjoy it but it felt like it worked.”
The third guinea pig, 27, who rode for 45 minutes at a
moderate pace, insisted that she had also received a good workout. She said,
“I am not sure I would want to go through the pain of 30-second sprints.”
A fitness expert for Reebok, who had not tried the study
protocol, thought that most people would not want to do it “because it is so
uncomfortable, but for those willing to endure it would work.”
Finally, an Olympic triple jump gold medallist offered a
more positive spin: “Going for a 40-minute run is not for everybody.
The idea of going and doing a short intense workout would appeal to people and
help them to embrace a healthier lifestyle.”
Anyone who has tried them both will tell you that 30
seconds “all-out” with 4 minutes rest is a walk in the park compared to the
Tabata protocol. Four minutes allows almost complete recovery—and time to
renew enthusiasm for another very hard 30 seconds. The heart of the
Tabata protocol is the 10-second rest interval, which allows partial recovery at
best. That’s the idea; incomplete recovery makes each rep harder than the
last, and brings you to the point of exhaustion on the last rep. Seven or eight
reps and you’re done, literally.
The longer rest period in the study under discussion was
probably a drawback in terms of effectiveness. On the other hand, the
three-day-a-week frequency was very likely an advantage. (The Tabata protocol
was done Monday through Friday with no rest days between exercise bouts.)
As noted above, the 20:10 work-to-rest ratio in the
Tabata study produced substantial improvement in both aerobic and anaerobic work
capacity, while the 30-second:4-minute ratio failed to
produce improvement in either category. As explained in article 10, the reason
almost certainly lies in the degree of overload. The Tabata protocol overloaded
both aerobic capacity and anaerobic capacity to the max, while the work-rest
ratio in the present study--the much longer rest periods in particular--probably
produced a sub-maximum overload.
In a later study, Dr.
Tabata compared the original protocol with an interval program very similar to
one under discussion. Each subject did 4-5 bouts of 30 seconds, with
2-minute rest periods, to exhaustion. Tests showed that the 20-second
intervals, with 10 seconds rest, overloaded both aerobic capacity and anaerobic
capacity maximally, while the longer interval protocol, with two-minute rest
periods, did not. In both respects, the stress produced by the second protocol
fell well short of maximum.
But why? Why did the
original protocol stress both aerobic and anaerobic capacity maximally, when the
more intense (200% VO2max
vs. 170%) and longer (30 seconds vs. 20) bouts of the second protocol did not?
Dr. Tabata and his colleagues believe the key factor was the difference in the
The relatively long
2-minute rest periods allowed oxygen uptake to fall
considerably and, therefore, when the next exercise bout started there was a
delay before the oxygen uptake increased and began again to approach maximum. On
the other hand, the short 10-second rest periods allowed only slight recovery,
and therefore oxygen uptake increased in each succeeding bout, reaching maximum
capacity in the final seconds of the last bout. The same was true for anaerobic
energy release. The 2-minute rest periods stopped the buildup of lactate and
allowed the resynthesis of phosphocreatine (see article 7, Diet & Nutrition,
on creatine) to occur.
Again, the short rest periods in original protocol caused the oxygen deficit to
continue building from rep to rep, reaching maximum anaerobic capacity at the
end of the exercise.
Almost surely, that's
why the current study failed to show improvement in aerobic and anaerobic
capacity. The 4-minute rest periods allowed almost complete recovery and maximum
stress was never achieved.
On the other hand, the
one or two days rest between workouts probably gave the current study a leg up
on the original Tabata protocol. The researchers believed that the rest days
would be an important advantage. “The importance of rest days between sprint
training sessions was emphasized in a recent study that showed that peak and
mean power elicited were unchanged after 14 consecutive days of sprint training;
however, when subjects performed the same number of training sessions over 6
weeks, with 1-2 days of rest between training sessions, power output improved
significantly,” they wrote in the study report. “Although numerous
mechanisms could potentially be involved, the importance of rest days between
training sessions may be related in part to the fact that strenuous exercise
leads to inactivation of cation pumps, and it has been speculated that up to
several days may be required for normalization of sarcoplasmic reticulum Ca2+
pump function.” Simply put, it takes a day or two for muscles to recharge
after very intense exercise.
So, it’s possible
that Dr. Tabata and his colleagues could have achieved even better results by
allowing their athletes a day or two to recover between workouts.
Another advantage of
the interval protocol under discussion is that more people are likely to be
willing to do intervals with 4-minute rest periods than with 10-seconds. Both
protocols are obviously hard, but the less demanding regimen probably has wider
appeal. It might turn more couch
potatoes into gym rats.
to the Wise
As noted above, interval sprints are not for everyone--certainly not for
people just getting started or those with health
problems. If you have doubts, by all means talk it over with your doctor.
Frankly, I enjoy high-intensity intervals; they're
challenging and leave no time for boredom. Not all the time, however. I make it a point to vary the work-rest ratio and cycle my
training. I don't train all-out all the time.
Generally, short hard intervals with long rest periods are
recommended to improve anaerobic capacity; and repetitions with short rest
periods are suggested to overload the aerobic system. The Tabata research and
the current study suggest that intensity--not volume--is the key to success.
It’s important to start a new regime at a manageable pace and ramp-up over
time as your condition improves. When you top out, change the plan and start
Train smart and keep in mind that you usually get out of a
program about what you put into it. That doesn’t mean more is better, however.
As the current study demonstrates, stress and rest are both important.
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