Pre- and Post-workout nutrition to maximize the training effect
Introducing the first installment of the Hypertrophy-Specific
Nutrition series.
by Bryan Haycock M.Sc., CSCS
bryan@thinkmuscle.com
Please send us your feedback on
this article.
Introduction
When implemented properly and consistently, strategic pre- and
post-workout supplementation can greatly increase the effectiveness of
your training. Without optimum nutritional strategies, the body's response
to training can only be considered a compromise at best. From this
perspective, training and diet can not be considered as separate factors.
The food and supplements that you take, and the work that you faithfully
perform in the gym, are both part of your training. On the day of
competition it will not be the athlete who trained harder who wins, it
will be the athlete who trained smarter.
Exercise causes acute changes in the metabolic environment of muscle
tissue. First there is a significant increase in blood flow to working
muscles. There is also a sharp increase in catecholamines (e.g.
noradrenalin, adrenalin). These changes favor catabolism during exercise,
and anabolism immediately after exercise. Because these changes are acute,
some lasting only a few hours, the pre and post exercise meals are
critical to optimizing the anabolic effect of exercise. This article will
discuss pre- and post-exercise nutritional strategies based on current
research in this area.
BEFORE
Pre-workout nutritional strategies are based on providing alternative
energy substrates (mainly carbohydrate) to preserve energy stores, and
taking advantage of increased blood flow to muscle tissue.
Carbohydrates
High intensity exercise places great demand on glycogen stores.
Glycogen is the sugar stored in the liver and muscles. Because high
intensity exercise burns energy at such a high rate, the body is unable to
supply sufficient oxygen to be able to use fat for fuel. Instead, it must
use sugar both stored in the muscle and brought in from the blood.
Consuming simple sugars right before training can reduce the amount of
glycogen used during exercise. This can prolong performance. More
importantly, higher glycogen and insulin levels appears to create a
hormonal milieu favorable to anabolism (growth).
During exercise, cortisol accelerates lipolysis, ketogenesis, and
proteolysis (protein breakdown). This happens in order to provide
additional fuel substrates for continued exercise. The effects of cortisol
may also be necessary to provide an amino acid pool from which the muscle
can rebuild new contractile proteins if there are insufficient amino acids
delivered from the blood. This ensures that some degree of adaptation can
occur regardless of the availability of dietary protein. Over time
however, if this process is not balanced with additional dietary protein,
the net effect will be only maintenance or even a decrease in functional
muscle tissue, as is evident during periods of starvation or prolonged
dieting. Fortunately, there is only a non-significant rise in cortisol
levels when carbohydrates were consumed during exercise. (Tarpenning,
1998) The net effect is a more rapid increase in the cross sectional area
of the muscle fibers with the greatest effect seen in type-II fibers.
This may be a less expensive option for those who were thinking of
using phosphatidylserine. In this case, carbohydrate administration
appears to down regulate the hypothalamic-pituitary-adrenal axis, probably
through insulin or perhaps through the presence of carbohydrate itself.
This would, in effect, greatly reduce the body's catabolic response to
exercise stress. All good news for bodybuilders.
Protein
Another pre-workout strategy involves taking advantage of increased
blood flow to working muscles. Because the availability of amino acids is
often the limiting factor for protein synthesis, a pre-workout protein
meal will enhance the delivery of amino acids to muscle tissue. Research
has demonstrated the effectiveness of a pre-workout protein drink.
Delivery of amino acids has been shown to be significantly greater
during the exercise bout when consumed pre-workout than after exercise
(Tipton, 2001). There is also a significant difference in amino acid
delivery in the 1st h after exercise, with the pre-exercise protein drink
providing a significant advantage. Net amino acid uptake across the muscle
is twice as high with a pre-workout protein drink as compared to consuming
it after. Phenylalanine disappearance rate, an indicator of muscle protein
synthesis from blood amino acids, was significantly higher when amino
acids were taken pre-workout. These results indicate that the response of
net muscle protein synthesis to consumption of a protein solution
immediately before resistance exercise is greater than when the solution
is consumed after exercise. This is primarily because of an increased
delivery of amino acids to the muscle.
AFTER
During exercise muscles use metabolic fuels at an accelerated rate. In
order for physical work to be continuous, the body mobilizes stored fuels
to make fatty acids, glucose, and amino acids available for oxidation.
This is a catabolic process and cannot occur simultaneous to anabolic
processes such as glycogen formation and protein synthesis.
In order for the body to recover from exercise, the catabolic
environment must be quickly changed to an anabolic environment. The food
that you eat after training effects the hormonal milieu in your body in
order for this to take place. With the rapid introduction of carbohydrate,
protein, and fat into the system post exercise, the body is able to begin
reparations on damaged tissue and replenish fuel reserves.
Carbohydrates
Carbohydrates are important for performance and perhaps more
importantly for glycogen recovery. Studies have shown an increased ability
of muscle tissue to take up serum glucose immediately following strenuous
exercise (Goodyear 1998). This is due to what is called, "non-insulin
dependent glucose uptake". After a meal, muscle cells transport glucose
across the cell membrane in response to the hormone insulin. Insulin binds
with its receptors at the cell surface causing a cascade of events that
ends with proteins, called glucose transporters, being translocated to the
cell surface. Once at the cell surface, these glucose transporters allow
glucose to pass through the membrane where they can be phosphorylated and
eventually stored as glycogen.
Membrane transport of glucose will exhibit saturation kinetics similar
to the effect of increasing substrate concentration on the activity of
enzymes. The rate of glucose entry into your muscle cells is limited by
the number of glucose transporters. Once all available glucose
transporters are associated with a glucose molecule, the rate of glucose
entry will go no higher.
There are at least 5 different classes of glucose transporter proteins.
They are designated GLUT1, GLUT2, GLUT3, GLUT4, and GLUT5. Each class of
GLUT protein differs in its kinetic parameters and are found in specific
tissues. GLUT-4 is the primary isoform regulated by insulin, and sensitive
to muscle contraction.
Muscle contractions, much like insulin, cause a separate set of GLUT-4
proteins to be temporarily translocated to the surface of the muscle cell
(Sherman 1996). This greatly increases the rate at which muscle tissue can
take in glucose from the blood after a bout of exercise. The effects of
exercise on glucose uptake lasts for a few hours into the post exercise
period. If the post exercise meal is lacking in carbohydrates, the
replenishment of glycogen is delayed. If carbohydrates are lacking in the
diet, exercise will cause a glucose deficit and glycogen stores will
continue to fall without being replenished to pre exercise levels.
There has been some controversy about which type of carbohydrate is
best for post exercise glycogen replenishment. Some argue that simple
sugars such as dextrose are best after exercise. Others say that drinks
with glucose polymers are best. Still others say that there is no need to
buy fancy sports drinks and that simply eating a meal high in
carbohydrates such as pasta or rice is sufficient. Studies have shown no
difference between different types of carbohydrates eaten post exercise
and the rate of glycogen replenishment as long as sufficient quantities of
carbohydrate are consumed (Burke 1997). Even when the post exercise meal
contains other macronutrients such as proteins and fats, the rate of
glycogen replenishment is not hindered, given there is sufficient
carbohydrate in the meal as well. These studies tell us that the
rate-limiting step in glycogen replenishment after exercise is not in
digestion or the glycemic index of a given source of carbohydrate. Over a
24 hour period it is the total amount of carbohydrate consumed that is
important.
The rate-limiting step in glucose uptake during exercise is determined
by the rate of phosphorylation once glucose has entered the muscle cell
(Halseth 1998). Glycogen synthase activity is also a possible
rate-limiting step (Halseth 1998). These processes are not readily
influenced by the composition of the "post exercise" meal, but rather by
the extent to which glycogen was depleted during exercise as well as the
amount of carbohydrate and fat consistently included in the diet.
It is recommended that at least 0.7 - 1.0 gram of carbohydrate per
kilogram body weight be consumed immediately after exercise and then again
1-2 hours later. If you experience gastric upset try increasing the amount
of water you consume with the carbs. Try to shoot for a total of 7-10
grams of carbohydrate per kilogram of body weight over a 24 hour period 3
for maximum glycogen storage. This may well be in excess of caloric needs
but it is important to shoot for this intake if glycogen storage is your
primary goal.
Protein
Protein is another critical nutrient post-exercise. Protein is
essential to post exercise anabolism. Protein provides amino acids which
are used to rebuild damaged tissues as well as provide enzymes and carrier
proteins necessary for adaptation to exercise. Without protein, which
supplies essential amino acids for endogenous protein synthesis, the
body's ability to adapt to exercise is greatly diminished.
Studies have shown a 12 to 14 day period after the onset of an
unaccustomed exercise program, in which nitrogen balance, the ratio of
protein intake to protein loss, is negative (Butterfield 1987). Any study
looking at protein needs and exercise must take this into account.
Nitrogen balance during this period appears to be insensitive to total
caloric intake, but can be improved with a high protein intake if adequate
calories are supplied (Gontzea 1975). Even though additional protein
intake will prevent nitrogen balance from becoming negative, it will still
fall despite high protein intake during the first two weeks of exercise.
Muscle specific messenger RNA (mRNA) produced subsequent to training
has a half life of only 4-5 hours. It is so short because mRNA has no
"quality control" mechanism built into the coding. By keeping the half
life short, any errors in the sequence won't be able to produce enough
defective proteins to do irreparable damage to the cell or organism. This
also allows tight control of protein metabolism.
The timing of protein intake is important. If the anabolic stimulus
from exercise is to be maximized, a steady flow of amino acids must bathe
the muscle while mRNA content is high. It should be no surprise that the
optimum time for protein intake after your workout is relatively brief
compared to frequency of training a particular muscle. Muscle protein
synthetic rate (MPS) is elevated in humans by up to 50% at about 4 hours
following a bout of heavy resistance training, and by 109% at 24 hours
following training. A study done by Macdougall (MacDougall et al 1995)
further examined the time course for elevated muscle protein synthesis by
examining its rate at 36 hrs following a bout of heavy resistance
training. Six healthy young men performed 12 sets of 6- to 12-RM elbow
flexion exercises with one arm while the opposite arm served as a control.
MPS was calculated from the in vivo rate of incorporation of L-[1,2-13C2]
leucine into biceps brachii of both arms over 11 hours. At an average time
of 36 hours post-exercise, MPS in the exercised arm had returned to within
14% of the control arm value, the difference being nonsignificant. The
following conclusions can be drawn from this study, following a bout of
heavy resistance training, muscle protein synthetic rate increases
rapidly, is more than double at 24 hours, and then declines rapidly so
that at 36 hours it has almost returned to baseline.
Current recommendations for total protein intake for athletes is
between 1.6-1.8 grams per kilogram body weight, depending on who you read,
however, it is not uncommon for bodybuilders to consume in excess of 2
grams per kg of body weight with no ill effects. It should be remembered
that the body does not have the capacity to effectively store amino acids.
Protein should be eaten at least every 3-4 hours. The evening meal should
contain slowly digesting protein that will allow a steady release of amino
acids into your system well into the night. Dinner is a perfect time for
steak or other meat dishes.
Fat
Little is known about the effects of fat in the "post-exercise" meal.
Total fat intake is probably more important for a bodybuilder than just
considering the post-workout meal.
Essential fatty acids in sufficient quantities have the ability to
alter physiology. Fatty acids such as omega-3s' and omega-6s', when
consumed in differing ratios in a consistent and deliberate manner, can
alter the composition of cell membranes which alters the production of
prostaglandins in working muscles and thereby can modify everything from
glucose transport to protein synthesis (Hayashi 1999). These effects are
seen after at least 5 days of consuming of these fats in moderate to high
doses. Eating them immediately after training and at no other time will
most likely not have any dramatic effect.
Some forms of fat may delay gastric emptying which theoretically could
slow the rate at which nutrients become available to tissues. We can only
speculate whether this would have any "long term" effect on gains. Most
research indicates that glycogen replenishment is delayed but not reduced
when gastric emptying is prolonged.
There is some indication that cholesterol may be an important nutrient
immediately after high intensity resistance exercise. Total cholesterol
has been shown to be significantly lowered for at least 90 hours following
a single bout of resistance exercise (Smith 1994). Serum cholesterol may
be needed for incorporation into damaged cell membranes after resistance
exercise. I'm not implying that you should eat a high cholesterol meal
right after training. Taken together, research is still lacking where the
optimal levels and composition of post-exercise fats are concerned.
Fluids
I couldn't really write an article about pre- and post exercise
nutrition without at least mentioning fluid replacement. Hydration is
extremely important on the cellular level. Muscle growth is inhibited by
dehydration. In bodybuilding we tend not to focus on fluid replacement
because, unlike runners or cyclists, most bodybuilders do not become
dehydrated after a single workout. The rate at which you become dehydrated
from training depends on how much you sweat (Gisolfi 1990). Some people
sweat a lot when lifting and others don't sweat a drop. A good rule of
thumb is to drink 1 ml for every calorie that you need. So, if you eat
3,500 calories a day, try to drink 3 1/2 liters. If you exercise in hot or
humid climates add 2 cups of water for every pound you lose while
exercising.
It's about synergy
As mentioned earlier, macronutrient intake modulates post-exercise
protein synthesis in ways that are just beginning to be understood. Yes,
protein is required to supply essential amino acids for protein synthesis,
but what is the mechanism by which protein is controlling this process?
Also, are carbohydrates and fats needed only for fuel replacement, or do
they play an "interactive" role in post exercise protein synthesis? Recent
research has shed light on these questions.
Researchers from the Division of Nutritional Sciences at the University
of Illinois examined the effect of post exercise meal composition on
protein synthesis. To do this, they looked specifically at the activity of
specific proteins known to regulate protein synthesis at the translational
level.
Initiation of translation (the binding of mRNA to the ribosomal
pre-initiation complex) requires group 4 eukaryotic initiation factors
(eIFs). These initiation factors interact with the mRNA in such a way that
makes translation (the construction of new proteins from the mRNA strand)
possible. Two eIFs, called eIF4A and eIF4B, act in concert to unwind the
mRNA strand. Another one called eIF4E binds to what is called the "cap
region" and is important for controlling which mRNA strands are translated
and also for stabilization of the mRNA strand. Finally, eIF4G is a large
polypeptide that acts as a scaffold or framework around which all of these
initiation factors and the mRNA and ribosome can be kept in place and
proper orientation for translation.
The researchers in this study looked at the association of the mRNA cap
binding protein eukaryotic initiation factor-4-E (eIF4E) with the
translational inhibitor 4E-eukaryotic initiation factor binding protein-1
(4E-BP1) in the acute modulation of skeletal muscle protein synthesis
during recovery from exercise. Fasting male rats were run on a treadmill
for 2 h at 26 m/min and were fed immediately after exercise with either
saline, a carbohydrate-only meal, or a nutritionally complete meal using
Ensure Powder (54.5% carbohydrate, 14% protein, and 31.5% fat). Exercised
animals and non-exercised controls were studied 1 h post-exercise.
Muscle protein synthesis decreased 26% after exercise and was
associated with a fourfold increase in the amount of eIF4E present in the
inactive eIF4E.4E-BP1 complex and a concomitant 71% decrease in the
association of eIF4E with eIF4G. Refeeding the complete meal, but not the
carbohydrate meal, increased muscle protein synthesis equal to controls,
despite similar plasma concentrations of insulin. Additionally,
eIF4E.4E-BP1 association was inversely related and eIF4E.eIF4G association
was positively correlated to muscle protein synthesis. This study
demonstrates that recovery of muscle protein synthesis after exercise is
related to the availability of eIF4E for 48S ribosomal complex formation,
and post-exercise meal composition influences recovery via modulation of
translation initiation.
The results of this study tell us a few things:
1. Insulin (via carbohydrate intake) alone is not enough to prevent
4E-BP1 from sequestering eIF4E. EIF4E must be free to bind to eIF4G in
order for protein synthesis (i.e. recovery from training and net muscle
growth) to begin. Insulin as well as amino acids must be present at the
same time as indicated by the results from the group that were fed a mixed
nutrient meal. So although feeding of the carbohydrate meal resulted in
elevated blood glucose and elevated insulin levels, carbohydrates alone
are not sufficient to allow protein synthesis to begin.
2. The only group that experienced a significant drop in cortisol
levels was the mixed meal group. The carbohydrate-only group showed that
neither blood glucose nor insulin had any effect on reducing cortisol
levels. In contrast, the mixed meal group showed cortisol levels even
below those in the control group who did no exercise and were also fed the
same meal.
It would have been nice for the authors of this experiment to have
explored the effect of the fat content in the "mixed meal". From the
results we saw that cortisol was lower in the mixed meal group. We can
only speculate whether this was due to the protein, the fat, or some
combination of protein, fat and carbs. Further research in this area
should take into consideration all components of the post exercise meal.
One other issue that might be addressed in humans is the time frame during
which re-alimentation is critical to "long term" adaptation to exercise.
In closing...
Pre- and post-exercise nutrition is critical if one wants to maximize
the anabolic effects of exercise. The pre-exercise meal should be high in
a quickly digestible protein. This will ensure high delivery of amino
acids to the muscle tissue. Carbohydrates can also be taken to minimize
glycogen loss and suppress catabolic hormones. Fat should be avoided
pre-exercise unless the exercise is for endurance.
The post exercise meal should consist of carbohydrate, protein and
perhaps a small amount of essential fats, in a form that is easily and
quickly digestible. There are many meal replacement products that fit the
bill. Just pick the one you like the most. Don't worry about sugar content
because right after a workout, fat storage is not a big issue. A liquid
meal is the most practical method of post-exercise feeding although it is
probably not essential. The ratio of macronutrients depends somewhat on
the nature of the training session. An emphasis on high glycemic carbs,
complete readily digestible proteins such as whey, egg, or high quality
casein, and essential fats such as fish or flax oil will meet the criteria
for an effective post exercise meal.
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