shown that six weeks of Wingate-based
SIT induced greater reductions in whole-
body fat mass and superior improvements
in cardiorespiratory fitness as compared
with energy-matched moderate-intensity
exercise in overweight and obese women.
More recently, Gibala’s team compared
moderate-intensity continuous exercise
with a short, time-saving interval workout.
The study showed that 12 weeks of sprint
interval training improved indices of
cardiometabolic health similar to traditional
endurance training despite a five-fold lower
exercise volume and time commitment.
The sprint protocol involved a total of 1
minute of ‘all out’ intermittent exercise set
within a 10-minute time commitment (3 x
20-seconds with ~ 2.5 minutes rest), whereas
moderate training consisted of 50 minutes
of continuous exercise, and both groups
trained three times per week. VO2max
increased similarly by 19% in both groups,
and there were comparable improvements
in insulin sensitivity as determined by
intravenous glucose tolerance tests.
Modes of exercise
One of the most important considerations for
HIIT is the mode of exercise being performed
during the session. Given that work output
is so high during the interval, a mentally
challenging or technically demanding
exercise mode is not recommended. Outside
of specificity for sports, coaches typically
recommend the use of stationary cycling,
rowing, running or one of the cross-country
skiing machine variations. These machines
allow for true session maximal efforts with a
lessened chance of sustaining an injury due
to poor mechanics or technique.
Measuring the work output and
training zones
There are two primary ways in which you can
measure your work output for each interval
session: internal or external monitoring.
Internal monitoring could use a heart rate
monitor or rate of perceived exertion, and
external monitoring could use speed or power.
If gauging heart rate, you need to know
what your maximal heart rate is and for
long or short intervals you would aim to
conduct the bulk of the work bouts between
90-95% of maximal heart rate. The goal of
these sessions is to accumulate 10 or more
minutes above 90% of HRmax. The heart
rate monitor is less useful for sprint interval
training, as these are conducted at best all-
out pace, for which a heart rate response is
not particularly accurate. Perceived exertion
would be a far better tool for this session type, as each bout should
feel as hard as possible.
An external monitoring approach to interval training would be
a percentage of peak aerobic speed, velocity or power. An easy
field test for this would be measuring your best speed, velocity or
power over 4 minutes. This corresponds quite nicely to one’s aerobic
maximum, when measured with an incremental test to exhaustion.
From here, one can set an appropriate speed, velocity or power
based on a percentage below, on or above VO2max. For example,
as an avid cyclist, my power over 4 minutes is ~500W. If performing
long intervals, I would aim to conduct my 6 x 3-minute intervals at
~88% of 500W (440W). For short intervals, I would go above this by
around ~20%, and a session of 6 x 20-seconds with 40 seconds rest
would be held at ~600W. For sprint interval training I would aim to hit
in excess of 800W (~170%).
Interval training for sporting performance vs. health
Research has shown that the time commitment for improving
cardiometabolic health using interval training is relatively small,
ranging from 10-30 minutes per workout. However, in well-trained
individuals, as one might expect, the volume/duration of interval
sessions appear to be greater. The majority of studies show that for
short or long interval sessions, the greatest improvements in VO2max
are seen with the sessions that accumulate more than 10 minutes of
work above 90% HRmax. This normally equates to interval session
duration of 40-60 minutes, including the warm ups and cool downs.
Warm ups for intervals
Warming up for an interval workout is a special art. You have to
consider taking yourself from a state of rest, up to the power, speed
or heart rate demands that the first interval will impose on you. If
you fail to do this, the consequences for the session will be severe!
Therefore 5-10 minutes is required to warm up the aerobic, anaerobic
and neuromuscular systems. As a general rule, spend the first 5
minutes incrementally increasing the heart rate until you spend a
minute, at minute six of the warm up, at around 90% of maximum.
Over the next few minutes, perform several sprints between 6-10
seconds to recruit the anaerobic and neuromuscular pathways.
Recover for a minute, and then perform your first interval.
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