Nutrient
Timing - The Future of Sports Nutrition
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In a new book called Nutrient Timing, exercise physiologist John Ivy,
Ph.D., and biochemist Robert Portman, Ph.D., argue that when athletes eat is as
important as what they eat. Citing dozens of recent studies, they make a solid
case.
Although Nutrient Timing is aimed primarily at an
audience of strength athletes, there is a lot of information in the book that
is valuable to endurance athletes as well.
Most endurance athletes are aware that it's
beneficial to drink a carbohydrate sports drink during exercise. But according
to the authors of Nutrient Timing, there are many other beneficial ways
to use nutrition during and after exercise that most endurance athletes don't
know about.
Here are five of them:
1. Consuming protein with carbohydrate
during exercise can increase endurance
It appears that the effectiveness of
carbohydrate consumption during exercise is limited by the maximum rate at
which the liver can release glucose into the bloodstream -- about 1 gram per
minute. It's not hard to consume enough carbohydrate in a sports drink to reach
this limit, and consuming any more will not help.
But the muscles can also use protein for
energy. A supplement combining carbohydrate and protein can therefore provide
more energy and delay fatigue by allowing the muscles to conserve more glycogen
(their main energy source).
A study at the University of Texas compared
the effects of a carbohydrate and a carbohydrate-protein supplement on
endurance performance. Trained cyclists last 36% longer in a ride to exhaustion
when fed the carbohydrate-protein drink than when fed the carbohydrate
drink.
2. Consuming protein during exercise can
reduce muscle damage
When protein is not consumed during
exercise, muscle proteins are broken down for energy, resulting in muscle
damage. When protein is consumed during exercise, such damage is minimized.
This was demonstrated in a study done at
James Madison University. Researchers fed either a regular carbohydrate sports
drink or a carbohydrate-protein drink to subjects during a hard stationary bike
ride and measured post-exercise levels of creatine phosphokinase (CPK) in the
blood. CPK is a biomarker of muscle damage.
The subjects receiving the
carbohydrate/protein supplement had CPK levels 83% lower than those receiving
the carbohydrate supplement, indicating significantly less muscle damage during
exercise.
3. The sooner you consume nutrients after
exercise, the more effective they are
The muscle cells are especially
insulin-sensitive for the first 45 minutes after exercise is completed. Insulin
transports glucose and amino acids into the muscle cells and stimulates muscle
protein and glycogen synthesis. Consuming carbohydrate and protein within this
45-minute window will therefore stimulate the muscle-recovery processes much
more powerfully than consuming the same nutrients later.
In a study at Vanderbilt University,
researchers looked at the effect of a carbohydrate-protein supplement on
protein synthesis following a 60-minute bout of exercise. Subjects were given
the supplement immediately after exercise or three hours later. Protein
synthesis was almost three times higher when the supplement was given
immediately after the workout. Other studies have shown a similar pattern with
respect to muscle glycogen replenishment.
4. Post-exercise nutrition reduces
injuries and sickness
In a remarkable new study, Marine recruits
representing six platoons were assigned to one of three treatment protocols
during 54 days of basic training. Each day after exercise, some Marines
received a carbohydrate drink, others a carbohydrate-protein drink, and still
others flavored water.
The investigators reported that the
protein-supplemented group had an average of 33% fewer total medical visits,
28% fewer visits due to bacterial/viral infections, 37% fewer visits due to
muscle/joint problems, and 83% fewer visits due to heat exhaustion compared to
members of the other groups. They also had less muscle soreness.
This new evidence indicates that athletes in
heavy training will stay healthier if they consume a carbohydrate-protein
supplement immediately following each workout. Strenuous exercise suppresses
the immune system, opening the door to infections. Carbohydrate and the amino
acid glutamine fuel the immune system and counteract this suppression.
5. Post-exercise nutrition improves
performance in the next workout
It stands to reason that if immediate
supplementation after exercise results in a faster, stronger recovery, it could
also improve performance in the next workout. The James Madison University
study cited above showed this to be the case.
After completing a performance ride on day
one, the subjects of this study were asked to come back after a 15-hour
recovery period. Upon returning, the subjects performed a ride to exhaustion at
85% of their VO2max. Subjects receiving the carbohydrate/protein drink during
the initial performance ride the day before were able to ride almost 40% longer
than those receiving the carbohydrate drink during the prior exercise.
Summary
The science of sports nutrition has come a
long way since the first sports drinks were formulated back in the '60s. It's
time to bring your sports nutrition practice into the 21st century. Nutrient Timing offers a compelling theory on
recovery nutrition, with a growing body of scientific evidence to support
it.
Nutrient Timing: The
Future of Sports Nutrition
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