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HEALTH&FITNESS
COMMENTARY:
RUNNING
April15
Wouldn’t it be great never to run out of fuel? Not
to hit the wall during a marathon? For the truly
fuel-efficient runner, that’s a reality. This month,
VERNE MAREE undergoes a fuel efficiency test
on the treadmill to find out more.
F
uel efficiency means burning more fat – of which
we all have more than enough; instead of only
carbohydrates – of which we’re able to store such
limited amounts. Taking about 15 minutes, the fuel
efficiency test is the second of two treadmill tests that you can
undergo, as the basis for setting endurance fitness goals. (I
described the first, lactate threshold, in last month’s Running
Commentary.)
The idea is to improve performance by building
aerobic
fitness
, which is a combination of the ability to do three things:
to effectively deliver oxygen to the muscles, to clear lacate, and
to use fat for fuel. Having identified your personalised heart
rate zones by means of the tests, you then follow a running
programme tailored to you and your goals. And, they say, you
can expect to start seeing results in the form of faster race
times in as little as three months.
But can it really help a middle-aged runner like me who
enters only 10K races? Yes, according to Chris, the fitness
consultant at the Journey Fitness lab: a strong aerobic base
is just as necessary for a 10K runner as it is for a marathoner.
That’s because aerobic running makes up such a high
proportion of the effort over all distances: it’s 99 percent for
the marathon, as you might expect, but still a whopping 96
percent for the 10K!
What about those elite marathoners flying along at 3:15
minutes per kilometre, for 42.2 kilometres in a row? (That’s
faster than most of us can sprint 100 metres!) They’re actually
highly aerobic, I’m told. Whereas the average Jo stops burning
fat when she hits 10kmper hour, an elite marathoner is burning
a good proportion of fat even at 20km/h. Even for the skinniest
Kenyan athlete – and that’s saying something! – fat is the main
source of energy.
Burn, Baby, Burn!
MaxiSports | Dreamstime.com
My Test
• I strap on the
yellow facemask,
make sure it’s
f a i r l y a i r t i gh t
and wonder if
my breath really
smells like this.
• Starting me off
at a 4km/h stroll,
t h e s o f t w a r e
attached to the
treadmill slowly adjusts its speed up to 13km/h
over a maximum period of 20 minutes.
• At the start, the monitor shows that I’m burning a
good proportion of fat to carbs; fat-burning peaks
at about 8.5 min/km before it starts coming down
and carb consumption begins to rise.
• Once fat-burning drops to zero, the test is over; for
me, this happens around the 15-minute mark.
Test Talk
Almost all the energy we burn is a combination of fat and
carbs. This fuel efficiency test takes a look at one’s current
fitness level from a fuelling standpoint; while you exercise, it
will be tracking the proportion of fat in relation to carbs that
you’re running on. (If you’re already glazing over, perhaps
skip the next paragraph.)
A mask worn over the face takes continual samples of what
the runner is breathing out. (Yes, that’s me in the photo; and
no, it’s not a good look.) These samples run through tubes
into an analyser that measures the respiratory exchange ratio
(RER): in other words, the ratio of oxygen to carbon dioxide
that you’re breathing out. The harder you exercise, the less
oxygen gets processed; so you’re producing less of the
carbon dioxide that results in your burning more carbs and
getting out of breath.