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 cannot 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.
Introduction
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 blood sugar and insulin levels
appear 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.
Amino Acids
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 hour 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 that when the solution is
consumed after exercise, primarily because of an increase in muscle
protein synthesis as a result of increased delivery of amino acids to
the leg.
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 affects 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 dependant 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 number of glucose transporters limits the rate of glucose entry
into your muscle cells. 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 is 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 last 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.
Simple vs. Complex
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.
Recommendation
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 that
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.
The Research
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.
Importance Of Timing
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.
Recommendations
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
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.
Research
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 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.
Protein Synthesis
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.
Results
The results of this study tell us a few things:
#1 | Insulin
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 | Cortisol Levels
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 explore 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 in 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.
