may help explain why keto diets have caught on among
ultrarunners but have made relatively little impact on
shorter Olympic distances like the marathon, since there
seems to be a clear efficiency penalty at marathon pace or
faster. And the wide range of individual responses may
help explain why the debate is so persistent: those who
say it works for them and those who say it doesn’t may
both be right.Alex Hutchinson is a Toronto journalist specializing in the
science of running and other endurance sports. His latest book,
ENDURE: Mind, Body and the Curiously Elastic Limits
of Human Performance, was published in 2018.supplement if you’re not sure if you
need to, because too much iron can be
as dangerous as too little. What consti-
tutes “ low” among endurance athletes
is an area of ongoing debate. If your
hemoglobin is below 115 grams per
litre, everyone agrees you need more
iron. For athletes, a recent review in the
European Journal of Applied Physiology
from the same Australian research
team, argues that normal hemoglobin
accompanied by ferritin levels below
20 micrograms per litre also signals a
need for supplementation.
Keto for runners
It’s a perennial topic of debate, and it’s
highly popular among ultrarunners.
However, there’s surprisingly little
research on the endurance effects of
low-carb, high-fat ketogenic diets. So
a new study from scientists in New
Zealand, published in Medicine &
Science in Sports & Exercise, merits alook. Eight runners spent two 31-day
periods eating either their habitual diet
or a tightly controlled keto diet, getting
78 per cent of their calories from fat and
just four per cent from carbohydrates.
They completed a series of before-and-
after physical tests on both diets.
At quicker paces, the picture was
clear: the ketogenic diet made the
runners less efficient, forcing them to
burn more energy to sustain the same
pace. At slower paces, there seemed to
be no difference between the two diets.
The dividing line was around 70 per
cent of VO2max, which is consider-
ably slower than marathon pace. In a
time-to-exhaustion run at 70 per cent of
VO2max, which took about four hours
on average, there was no difference
between the two conditions on average:
five of the runners gave up sooner on
keto, but three of them lasted longer.
These somewhat mixed result won’t
really settle any debates. However, itrunningmagazine.ca Canadian Running 33bodywork column
the science of runningMY LIGHT
MY NIGHT RUN
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thrill. You never know what will happen next in this
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totally magical way. It’s a moment of empowerment
over the city, over strangers, loners and anyone
who crosses your path. // #petzlnightrunningBINDI
Ultra-light, rechargeable headlamp designed for everyday uses.
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