Completing a half marathon has been on your bucket list for ages.
You finally round up a bunch of friends and sign up for a charity run in six
months after one of your training sessions a friend suggests that you
should add protein to your diet to perform better on your run but another
friend tells you that loading up on carbs is better for endurance so who's
right if you're into endurance training like cycling or long-distance running
should you focus on carbs or protein
first let's have a look at what happens inside a muscle during exercise all
dynamic forms of exercise like running require contraction of your muscle to
generate force and then relaxation so that the cycle can repeat itself deep
down inside a muscle there are two long fibers called actin and myosin for a
muscle to contract and generate force myosin needs to grab the actin fiber and
pull it of course all of this doesn't happen on its own muscles need energy to
make the magic happen when myosin pulls an actin fiber the main fuel being
burned is called adenosine triphosphate also known as ATP think of a muscle like
the engine of a petrol thirsty car each muscle contains a small store of ATP
which is only enough to last for about three seconds of muscle contraction so
muscles need a way to continuously refuel and make new ATP well the body
has three energy storage tanks that it draws upon to power this ATP guzzling
machine first is creatine phosphate muscles
break down creatine to rapidly make new ATP but creatine can only generate
enough ATP to power a muscle for about 10 seconds so creatine is good for short
bursts of muscle power like when lifting weights but not so good for endurance
then there's a second tank the glycogen lactic acid system glycogen is a stored
form of carbohydrates when you eat a slice of bread the carbs that your body
doesn't use immediately is stored in the form of glycogen all body cells can
store glycogen to some extent but your liver and muscle cells can store
especially large amounts when muscle sense that the ATP and creatine stores
are running low muscles start breaking down
glycogen into glucose when there isn't a lot of oxygen available this glucose is
converted into lactic acid which leads to the production of ATP the glycogen
lactic acid system can power muscles for about one and a half minutes which is
much better than the ten seconds of the creatine system but not enough to get
you through a half marathon also lactic acid causes extreme muscle fatigue the
final trick of the body sleeve is the aerobic system here glycogen is broken
down into glucose then to pyruvic acid but rather than being converted into
lactic acid pyruvic acid is instead sent to a powerful place in the cell called
the mitochondria in the mitochondria pyruvic acid reacts with oxygen to
produce enormous amounts of ATP so to recap stored ATP and creatine can
power a muscle for about 10 seconds the glycogen lactic acid system powers the
body for about one and a half minutes but what about the aerobic system well
it is essentially unlimited as long as there are enough nutrients the aerobic
system will continue to pump out ATP but what happens when the body runs low on
glycogen well fat stores can be broken down to make significant amounts of ATP
and it can also convert protein into glucose but this process is not very
efficient so in order of priority the body likes to use glycogen first then
fats and protein only as a last resort so now that we know that the body likes
to use carbs and fats for energy let's see which type of diet performs best for
endurance training a high carbohydrate diet a high fat diet or a mixed diet on
the left is a percentage of energy coming from carbs with zero percent on
the bottom and 100% on the top on the right is the percentage of energy
sourced from fats with zero percent on the top and a hundred percent on the
bottom for an athlete on a mixed diet initially all the energy comes from
carbs but they used up fairly quickly at four minutes of activity about 75% of
energy is from carbs and 25 percent is from fats at two hours the athlete
reaches exhaustion at that point fats providing most of the energy with only
35% coming from carbs what about a high-fat diet even at the start of the
event only 80% of the energy is from carbs with fats providing the remaining
20% mainly due to low glycogen stores the athlete reaches exhaustion at about
1 and a half hours into the event but the story is very different for a high carb
diet the glycogen stores are so abundant that even at one hour into the event
around three-quarters of energy is from carbs and the remaining 25% from fats
the athlete reaches exhaustion at the four hour mark which is about two hours
longer than a mixed diet when recovering after an event an athlete on a fat and
protein diet takes a long time to recover their muscle glycogen stores but
an athlete on a high carb diet can rapidly regain the muscle glycogen
stores of the first 40 hours of recovery so high carb diets easily outperform a
mixed or high-fat diet but is there still a role for protein in one study
cyclists were put on a high-protein moderate carbohydrate diet for seven
days and then completed a Time Trial they were then put on a high carb
moderate protein diet for seven days and completed another Time Trial the
sequence of the two diets was randomized the results showed that cyclists on a
high-protein diet took about 20% longer to complete the
time trial compared to the cyclists on the high carb diet but some studies do
show that adding protein can reduce blood markers of muscle damage and
improve feelings of muscle soreness after a grueling event so it is thought
that adding protein to a high carb diet can assist with the recovery and help
offset muscle damage there are three take-home points if you're training for
an endurance events like a half marathon you should focus on a high carb diet one
study recommends getting six to ten grams of carbs per kilo of body weight
per day second muscles need about 48 hours to build up
the glycogen stores even on a high carb diet which means that you shouldn't do
any high-intensity exercise for two days before a big event
and finally protein supplementation may assist with recovery one study
recommends an intake of 0.25 grams of protein per kilo of body weight per hour
of endurance exercise thanks for watching and I'll see you in the next
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