GEAR » RUNNING SHOES
First, the midsole shape is a rocker
design, second, the midsole material is
something called Pebax foam, and third,
there’s a much-discussed carbon fibre
spring plate. The differences between
the previous version, the Vaporfly 4%,
and the Next% is that the Next% has
a thicker forefoot that takes the drop
down to 8mm (Nike didn’t lower the
heel thickness) and a better forefoot
outsole. There are also changes to the
upper material so that it doesn’t become
waterlogged. The carbon plate remains
the same. So was it the shoe that won
the race for Kipchoge, or is he just a
phenomenal athlete?
CAN THESE NEW
TECHNOLOGIES
HELP TRIATHLETES?
Nike ZoomX Vaporfly Next%
The winner of the biggest hype in the
shoe world has to go to the Nike ZoomX
Vaporfly Next%, which debuted at the
London Marathon in April on the fleetfeet
of Mo Farah and Eliud Kipchoge. The
Vaporfly technology here is threefold.
The actual biomechanics of running
don’t differ between the sport of running
and the sport of triathlon. But whereas a
pure runner starts their race with a fresh
set of legs, a triathlete starts the run
with fatigue in their quads, and muscle
shortening in their calves and hamstrings
– and that can be where the origin of
some of their injuries lie. Triathletes
know only too well that their legs need a
reboot at the start of their run and that it
can take time for them to settle into the
rhythm of a comfortable run.
Tired legs mean your normal pattern in
running will be compromised. You may
not be able to go to your normal stride
length and as a consequence increase
your cadence. You may not be able to
control your forefoot speed from heel
strike and get a forefoot slap. Toeing
off may be compromised because your
calves are tight and tired. You can’t
control the flexion at your knees because
of quad fatigue, and all of this may take
time to settle.
It is now known that one of the biggest
predictors of running injuries comes
from something called “the peak braking
force”. This is the force that stops your
foot when you land on the floor. It should
be well controlled by the muscles in your
legs and your core (yes, strength training
is a real need) but the more fatigued
you are, the less able your body is to
cope with this force, and the greater the
damage it can do.
Can a shoe help? A thick stack in the
midsole, together with softer density,
more responsive materials (material
that absorbs and returns the energy),
may be responsible for decelerating and
dissipating this force. The thick stack will
compress to absorb the impact that your
legs may battle with in the beginning.
Know your shoe jargon
Heel drop refers to the
difference between the
thickness of the heel of the
shoe, and the thickness of
the forefoot. Heel minus
forefoot equals the drop.
Traditional shoes used to
be 10mm to 14mm. The
minimalist era around 2013
saw shoes go from 12 down
to 0mm. Now the drop
can be 0mm, 4mm, 8mm,
10mm or 12mm. Some
shoes have a certain drop
written into their DNA. For
example, an Altra will always
be a zero drop whereas the
Saucony Kinvara has
98
always had a 4mm drop.
The ride is the feel you
get from the shoe as you
move from initial contact to
toe off. Manufacturers are
trying to develop shoes that
assist this, so you expend
less energy in running. A
good tip when you put on a
shoe: if it feels like you are
working against the shape
of the sole profile when you
walk or run, don’t choose it.
Responsiveness comes
from the material in the
midsole and sock liner. You
want to feel that the midsole
material is not collapsing
under the foot. It should
offer cushioning but return
back to original size quickly
so that your foot isn’t on a
collapsing substrate (think
of running on a beach). The
reverse is also true. The
shoe shouldn’t be too hard.
This is where good running
store staff will try to match
a midsole density that suits
your body weight. Putting
a heavy person on a soft
shoe or the other way
around could potentially
mean an injury, or a short
life for the shoe.
Energy return is similar
to responsiveness, or more
simply put, compression
and release. Manufacturers
claim shoes can return
energy, so you don’t fatigue.
I always question this – in
pure physics there is no
free energy anywhere, ever!
You get out what you put
in. Simply explained, if you
compress a shoe using
your energy, you only get
that much back and no
more. If the shoe loses the
energy you put into it, over
a distance, that means the
shoe can be responsible for
fatiguing you.