This document discusses the physiological processes that occur in the body during an off-road marathon. It explains that core body temperature rises significantly, which causes sweating for cooling. Dehydration occurs which triggers anti-diuretic hormone to conserve water. Digestion is disrupted as blood is shunted to working muscles. Feet and ankles swell from increased blood volume and capillary expansion. The heart grows stronger to cope with demands. Proper training enhances fitness and ability to utilize fat stores for fuel, improving performance and reducing injury risks of an uneven trail surface.

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THE SCIENCE BEHIND...
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THE SCIENCE BEHIND...
WHAT IT DOES
MARA
What’s going on behind the scenes, inside a hot, sweaty human being during an
THON:TO YOUR BODYoff-road marathon? Rob Kemp asks two scientists to investigate your inner workings

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THE SCIENCE BEHIND...
EXPERT ADVICE
What if you run
even further?
If conquering a 26.2-miler isn’t
enough then taking on longer
challenges may be more rewarding –
and not necessarily as daunting…
■ ULTRAMARATHONS Researchers
from Stanford University in the
US, examining the after effects
of ultramarathon runs, found that
overall post-race injury figures
were lower for ultras than those in
26.2-mile events. They concluded
that this may be due to more
experienced runners being less prone
to injury and that ultramarathon
competitors have an established
marathon pedigree.
The results also showed that the
ultrarunners had a very low incidence
of high blood pressure and irregular
heartbeats. Less than 1% had been
diagnosed with heart disease or had
a past stroke. Ultramarathon runners
are less prone to stress fractures than
shorter distance runners. However,
in those that do run ultras, 48% of all
reported stress fractures were foot
ones, leading researchers to pinpoint
uneven terrain as the chief cause.
■ 100 MILES PLUS The equivalent
of 5.5 regular marathons, in which
you’re carrying everything you need
with you in a backpack, tests the steel
of the most hardened of runners.
The length of the recovery period is
pretty epic, too. Runners who build
up a high mileage base often recover
quickest. The benchmark recovery
time for a 50-mile ultra can be 2-3
weeks before you’re able to handle
normal training loads again. For the
100-mile or more event 6-8 weeks
or more isn’t uncommon. Factor this
into your year’s plan.
MEET THE EXPERTS
Dr Steve Faulkner is
a coach, triathlete
and research
associate in
Exercise Physiology
at Loughborough
University. Follow
him on Twitter:
@SHFaulkner
Michael Harrison-
Blount is a Lecturer
in Podiatry at
the University of
Salford, studying
for a PhD. He
has eight years
experience working
for the NHS.
Y
ou’re at the start line of an
off-road marathon, a hill
rising ahead. The mud is
thick, the clouds are low.
You’ve been training for this
for months and adrenaline is pumping.
Last minute gel-check, the whistle goes,
you’re off! It’s the start of a tough few
hours; your legs will burn, your lungs
strain and heart rate rocket. But what
else is going on? What does your body
get up to, unseen, to get you through?
Hundreds of different processes are
taking place, with little to no conscious
input from you. Here we find out what
they are and why they’re so important.
What happens?
Let’s start at the beginning. Within 30
minutes of setting off on this 26.2 mile
run, your body temperature will have
risen from its usual 37°C to about 40°C.
You start to sweat, the liquid on your
skin pleasantly cooling in the breeze.
When it evaporates it leaves behind
a light dusting of abrasive salt and
minerals. Watch out – you’re now in
chafing territory.
This means you’re also now more
dehydrated, so the pituitary gland in
the brain raises the body’s production
of anti-diuretic hormone which, in turn,
tells the kidneys to absorb more water.
This keeps it in the body, preventing it
being lost through urine and ensuring
blood/water level is high enough during
your race. If you’ve noticed your urine is
darker when you’re dehydrated, this is
why. Time to look out for a drink station!
And, er, a toilet. Your digestive system
can be sensitive to stress – especially
the rigours of marathon running – and
many trailers find mid-race that they
need to make an emergency exit to the
nearest bush. This is why it’s a bad idea
to introduce new foods or drinks on race
day. Stick to what your body knows.
One 2008 study on 1281 Dutch
runners found that at least 45%
complained of a gastrointestinal issue
during the run. This happens as
the blood which usually helps keep
your digestive system in good nick
is rerouted to leg muscles, heart and
lungs, powering you over those miles.
This in turn upsets fluid absorption
and processing. Increased dehydration
is the happy result of this, and can
lead to cramps as well as that sudden,
desperate need for a ‘comfort break’.
So you should drink more water,
right? Lots in fact! Well, yes, but the
latest thinking is to drink to thirst
rather than purposefully over-
hydrate - this can strain your
cardiovascular system which is
already working hard to deliver
oxygenated blood to your
desperate muscles.
You might also notice
towards the end
of your marathon
that your shoes are
feeling snug. What’s
going on there? Swelling
in your feet and ankles is
caused by a combination
of factors: raised blood
volume, inflammation
through foot impact with the ground,
and the expansion of your capillaries.
These tiny blood vessels expand to carry
higher levels of oxygen and blood to the
muscles, which are crying out for fuel.
And it’s not just miniscule capillaries.
Your heart – working hard now –
expands during the race to cope with
increased oxygen demand and blood
volume. Over time, during races and
training, it will physically grow and
adapt to conserve energy, assisting you
to run faster for longer. Like any muscle,
it becomes more efficient with exercise,
so your resting heart rate will drop.
Meanwhile, especially from 20 miles
onwards, your brain is being tested
too. Running a trail marathon requires
mental strength as well as physical
fitness. The body’s
preferred fuel is
glycogen and, as
stores deplete,
the brain can be
affected by the
lack of energy.
Runners can hit a
mental wall where
lightheadedness and
pain can trigger anxiety and self-doubt.
This is where fitness comes in.
Why fitness counts
Elements of self-doubt may occur a lot
earlier if you haven’t trained right for a
trail marathon. Lack of fitness means the
body has to work much harder. “You’re
more likely to fatigue faster due to a
rapid depletion of carbohydrate (carb)
stores,” says Loughborough University
exercise physiology researcher Dr Steve
Faulkner. The small-engined, unfit body
burns more fuel, faster, to do less, so you
get fatigued. Get fitter and you’ve just
upgraded from Fiesta to Ferrari.
Training for a trail marathon isn’t just
about knocking out the miles, either. If
you follow a proven training and diet
plan then you’ll have been taking on the
right nutrients, especially carbohydrates,
ensuring your glycogen levels are tip-top
on race day. But that’s not the only fuel.
Fat is harder to convert to energy but it’s
almost limitless and burns more slowly.
“A well-trained runner will be able to
meet more of their energy requirements
from fats – though carbs will still be the
primary fuel source.” says Steve.
How trail differs to road
“One of the issues specific to running a
trail marathon will be a lack of general,
overall conditioning that you simply
wouldn’t get with road running,” says
Steve. You shouldn’t expect to run well
on trails if you don’t run on trails in
training. Makes sense? Steve says,
“The additional joint and muscle stability
you get from training on trails will help
you cope with varying terrain, uneven
surfaces and continually changing
gradients. A lack of conditioning will
likely result in injury and sub-optimal
running off-road.”
Adapting to the demands of an
unstable course and dealing with
the mental and biological challenges
therefore make specialised training for
a trail marathon essential. “For starters,
it’s likely that a trail marathon will be
a lot hillier than one on the road,” says
Steve. “The energy cost will almost
certainly be higher due to this increased
workload. Plus, you’ll be activating
core muscles to give additional stability
on uneven ground. This will drain
your energy even
more.” With both
running and core
strength training,
your performance
will improve but,
more importantly,
you’ll enjoy a trail
marathon way
more and your
body will suffer less from the affects of
this 26.2 mile pounding.
Ace 26 miles off-road
If you’re entering your first trail
marathon a few key elements should
feature in your training plan. To begin,
training should be gradual, allowing
time to build up to your target distance.
If you’re currently running regular but
relatively short distances (say, 6 miles,
two or three times per week) then 10
weeks of focused training should be
enough to raise your stamina and fitness
levels enough to complete a marathon.
The right plan should include
Like any muscle, your
heart becomes more
efficient with exercise,
so your resting heart
rate drops
Wearing proper
running socks
will reduce
friction and goes
a long way to
stopping blisters
developing
➜
Trail running champion
Ricky Lightfoot focuses
on all-over body strength,
not just trail running.
OPENINGIMAGE:IMAGEBROKER/ALAMY

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THE SCIENCE BEHIND...
➜
EXPERT ADVICE
Recover more quickly
from a marathon
Putting your body through a
gruelling few hours can take days
to overcome. But follow the right
recovery routine and you can speed
up that repair process.
■ ACTIVELY RECOVER Walk or jog
beyond the finish line to allow your
body to cool down slowly and get
back to its resting state. It’s just been
highly stressed and needs time to
adapt downwards.
■ TOP UP CARBS AND PROTEIN
American College of Sports Medicine
research shows that a mix of protein
and carbohydrate taken immediately
after running restores glycogen
and amino acid levels
much faster than a
carbohydrate
solution only.
The carb-
protein
combo will
double
the insulin
response and
increase the rate of glycogen
synthesis (deposit of sugar into
muscle cells) by 30%.
■ FEEL YOURSELF Post-race
massage may help manage muscle
inflammation, assist blood circulation
and reduce the risk of cramps. Avoid
any deep-tissue sessions in the days
immediately after a marathon as
the tissue is still in a state of repair,
but learning some light touch self-
massage could help speed up your
recovery.
■ KEEP THINGS FLUID
University of Texas studies
show that getting glycogen
into your system within
the first two hours of a
marathon is the most
crucial – and that drinks
are the quickest way
to enhance muscle-
glycogen restoration
because fluid absorption
is faster than digestion
of solid carbohydrate
foods. Pack an energy
drink, fruit smoothie or
squash with a teaspoon
of sugar and pinch of
salt in your bag for straight
after the race.
■ LEAVE IT A WEEK A post-race run
won’t help you recover faster from
a marathon – research from Ohio
University suggests it can actually
hinder your glycogen repletion and
recovery of leg-extension strength.
Grab the excuse to take it easy with
walking instead of running.
easy runs, at least one long trail, and
some speedwork each week – plus that
all important rest day. Don’t skip this.
Your body needs easier days to adapt to
increased training levels. Substances like
growth hormones only kick in when the
body is fully rested. So, at least once a
week take your foot off the gas.
If you can, also include cross-training
sessions like cycling or swimming, which
will help raise your cardiovascular
fitness and aid your endurance.
Does sex matter?
Hot topic time! Does the body react
differently to a marathon if you’re a
woman or a man? “Research shows that
the gender gap in performance gradually
reduces as the length of the event
increases,” says Steve.
It’s thought that this is due to the
greater reliance on fat oxidation as fuel
as duration increases and intensity is
reduced, causing a shift away from carbs
to fat as the primary fuel source. “As
females naturally tend to have greater
fat deposits, it is likely that they may
benefit from longer races where the
intensity of exercise is much lower,”
says Steve. “But, in the world of
sports science, there is much debate
surrounding this.”
So, if men and women burn energy
slightly differently, does that mean they
should fuel differently too? Research
from the Journal of Applied Physiology
suggests that while ‘carb-loading’ –
stuffing your pre-race face with pasta
or porridge – may be beneficial for male
runners, it may not make any difference
for women. Because women burn a
higher percentage of fat than men,
the glycogen-storing purpose of carb
loading may not be as advantageous. So
according to this research, men, stuff on.
Women, sadly, notice the word, ‘may’.
More bad news for the X-chromosome
– further studies featuring female
endurance athletes who carb-loaded, ate
carb-based gels mid-race or both, found
the women burned more carbs and less
fat than usual but did not experience
an increased performance in response.
If this is all correct, it implies lower
intensity training, teaching your body to
burn fat as fuel, could be most beneficial
to female trail runners.
Recover faster
So, you’ve trained for weeks, you’ve
the calf muscles of a Spartan and
your resting heart rate is a slow
steady thud. You ran fast and
your recovery should be just
as quick, right? If only!
Your body has just been under
a high level of stress and it takes
time for it to return to normal. The
battering your joints take from a
26.2-mile off-road run mean they
require at least a week of restful
activity. Anything that doesn’t resolve
itself or feels like sharp pain rather
than a dull ache, see a physio.
It’s not just
muscles that take
a battering. “The
The right plan should include easy runs, at least
one long trail, and some speedwork each week,
plus that all important rest day
It’ll be tempting to
run faster than you
should on race day;
stick to your pace
and finish strongly
The performance
gap between
men and
women
reduces at
longer
distances

4. TRAIL RUNNING 49
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THE SCIENCE BEHIND...
immune response to endurance events
such as marathons, ultras and intense
training can be quite impactful,” warns
Steve. “There’s a great deal of evidence
to show that when exercise starts to
become extreme then the immune
system can actually be compromised
and athletes will become more
susceptible to illness, particularly upper
respiratory tract infections, like coughs
and colds. The key is recovery between
races, which allows the acute immune
response to recover to its baseline. The
first 24-48 hours afterwards is when
you’re most susceptible to infection.”
Get fully rested before pushing it again.
But the most common post-trail-
marathon injury? Bet you can guess.
“Blisters, caused by friction,” says
Michael Harrison-Blount, Lecturer in
Podiatry at the University of Salford.
“Prevention includes wearing shoes that
fit you right, socks that don’t slip down
and for some, the use of a lubricant.”
Toenails are common casualties too.
“Blackened, bruised and even detached
toenails occur as changes in direction
and a greater amount of downhill
running stress these points.” Cut your
toenails before the race or say goodbye!
Is age a drawback?
While brilliant fitness, stamina, patience
and tonnes more experience sees older
runners outperforming the youngsters,
there are still some basic physiological
facts those over 50 need to consider
during post-marathon recovery.
“Even lifelong runners feel more tired
after certain sessions compared with
when they were younger,” says Steve.
“There’s data to support the anecdotal
evidence that recovery slows with
age. The molecular and biochemical
processes that underpin recovery do
slow with age.” The easiest way around
this is to simply pay attention to how you
feel. Don’t push too hard the first few
weeks after a long race. Sleep more, eat
well and keep the pace gentle.
You can do it!
Your body is a powerhouse, capable
of hundreds of intricate processes. So
whatever age, sex or ability level you
are, train hard and rest harder to ace
your trail marathon. Running 26.2 miles
off-road will push you harder physically
and mentally than the equivalent over
flat terrain. That’s why we like it!
MARATHON
MYTHS BUSTED!
MYTH LACTIC ACID IS
THE CAUSE OF THE PAIN
Lactic acid, the side-effect substance
of glucose being broken down
and oxidised to create energy, is
produced in greater amounts during
a trail marathon. This leads to a surge
of hydrogen ions in the body – those
ions specifically cause a greater
burning sensation in the muscles.
MYTH MASSAGE HELPS
FLUSH OUT TOXINS
Massage will relax clenched
muscles but it won’t flush out or
disperse lactic acid. You can’t
physiologically rub those toxins out
of the bloodstream, but massage
will reduce the intensity of Delayed-
Onset Muscle Soreness (DOMS).
MYTH MY MUSCLES WILL BE
FULLY RECOVERED IN 48 HOURS
Trail marathons make demands of
muscles that differ greatly from road
running. “I’d expect to see a greater
increase in muscle pain (DOMS)
72-96 hours after the event due
to the large eccentric muscle
contractions involved in downhill
running,” says Dr Steve Faulkner.
MYTH BIGGER SHOES
WILL COMBAT BLISTERS
“I’ve had patients try everything to
combat blisters,” explains podiatrist
Michael Harrison-Blount. “One man
covered his feet in duct tape. A 1cm
gap around the toes is plenty without
constricting the foot when it swells.”
MYTH I’M NOT FULLY REHYDRATED
UNTIL MY PEE RUNS CLEAR
Pale yellow, if you’re testing the
‘strength’ of your urine is fine. The
shade to look out for post-run is
a dark one (like apple juice) and a
strong odour. That’s a sign you need
to take on more fluid.
Get fully rested before
pushing again. If you
feel fatigued, sleep
more, eat well and keep
the pace gentle
This could be you!
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