Post-exercise recovery after dietary protein ingestion in healthy young men

Resistance exercise and protein ingestion can act separately and
synergistically to stimulate muscle protein synthesis rates. This synergy of
muscle contraction and protein ingestion provides the basis for
training-mediated hypertrophy. Many workers have manipulated post-exercise
feeding paradigms in an attempt to define the *optimal* protein source to
consume to support muscle protein accretion. Original work was performed using
intravenous infusion of mixed amino acids or bolus ingestion of mixtures of
crystalline amino acids; however, consuming free amino acids rarely occurs in
normal dietary situations. Currently, there has been a great deal of interest
in studying the capacity of dairy proteins to stimulate postexercise muscle
protein synthesis rates and promote training-mediated hypertrophy. Dairy
proteins represent an attractive protein source for researchers to study
because they are rapidly digested/absorbed and contain a high proportional of
essential amino acid, especially leucine. Both of these characteristics, speed
of digestion/absorption and peak amplitude in leucinemia, are fundamental for
the maximal stimulation of muscle protein synthesis rates after protein
ingestion. However, very little is known about the effects of other types of
high-quality animal proteins, such as beef, on stimulating post-exercise muscle
protein synthesis rates. Beef is considered a high-quality and widely consumed
protein source. Importantly, a 113-g serving of beef contains 30 g of protein
(~10 g essential amino acids; ~2 g leucine) and is similar in amino acid
composition to that of milk proteins. Certainly, some evidence suggests that
the synergistic effect of exercise and feeding on muscle protein synthesis
rates is still apparent after consumption of beef. However, the workers did not
compare this response to a group that consumed an alternative high-quality
isonitrogenous-matched animal-derived protein source. As a result, it can only
be speculated on the capacity of beef to stimulate muscle protein synthesis
rates as compared to milk proteins during postexercise recovery.
In the present study, we wish to determine the impact of single meal-like
amount of minced beef or dairy milk on digestion and absorption kinetics and
postexercise muscle protein synthesis rates. This study will be the first to
directly compare two commonly consumed protein-rich food items on muscle
protein synthesis rates in healthy young men. This information will be highly
relevant for developing nutritional interventions for maintaining and accruing
muscle mass.

To determine whether the intake of minced beef is equally effective as
ingestion of a bovine milk protein beverage in stimulating post resistance
exercise muscle protein synthesis rates in young men.

The present study employs a crossover design. In total, 12 healthy young male
subjects will be included in the study. Subjects will be randomly assigned to
consume minced beef or milk during trial one. During the test day, subjects
will perform leg extension exercise and immediately afterwards consume 35 g of
protein either as minced beef or milk. Approximately, two weeks later subjects
will return to the laboratory for the identical experimental procedures as
trial 1, which includes exercise that is worked-match to trial 1 and
consumption of alternative protein source that was not consumed in trial 1.

protein type, bovine milk or minced beef

The risks involved in participating in this experiment are minimal. Insertion
of the catheters in a vein is comparable to a normal blood draw and the only
risk is of a small local hematoma. Minimal risk is also true for the muscle
biopsy. The incision made for obtaining the muscle biopsy will be performed by
an experienced physician and will heal completely. Within our research group we
have extensive experience with taking muscle biopsies. During the follow up
several days after taking the biopsy no complications have been reported.

The milk protein beverages contain normal nutritional ingredients and for this
reason do not form any health risks. The vacuum-packed and pre-weighed meat
meals are normal food products and have been cleared for human consumption. The
labeled amino acids tracers applied in this experiment are not radioactive and
are completely safe. The production of the tracers for intravenous
administration will occur in a sterile environment according to GMP guidelines.

There are no complications associated with the procedure of a DEXA scan. The
level of radiation emitted during a DEXA is very low, <1 *Sv. This is very
minimal exposure compared to the total background radiation level per year in
the Netherlands, which is approximately 2.5 mSv/year.