Cold and hot water immersion as a strategy to promote post-exercise recovery in healthy young men.

Cold- and hot-water immersion (CWI/HWI) are frequently applied strategies to
accelerate post-exercise recovery in both recreational as well as professional
athletes. Another important recovery strategy for athletes is to ingest proper
post-exercise nutrition (i.e., protein and carbohydrate) in order to replete
endogenous glycogen stores and augment the skeletal muscle adaptive response to
exercise. However, the effect of repeated post-exercise CWI on muscle protein
synthesis and subsequent muscle recovery has never been assessed. In addition,
it is not clear what the acute effect is of post-exercise CWI or HWI on muscle
protein synthesis and glycogen repletion following food ingestion.

To assess the effect of a 2 week resistance exercise training program combined
with CWI on muscle protein synthesis and the reponse to the ingestion of a
single bolus of protein and carbohydrate after post-exercise CWI or HWI on
muscle protein synthesis and glycogen repletion in healthy young males.

A controlled intervention study.

Healthy, young men will be assigned to a 2-week resistance type exercise period
combined with cold-water immersion (CWI) to assess the effect on muscle protein
synthesis. We will apply 2H2O measurements during repeated CWI sessions
following exercise to measure muscle protein synthesis.
In another group, healthy, young men will be assigned to a single bout of
resistance type exercise followed by hot-water immersion (HWI) to assess the
effect on muscle protein synthesis. Following each session, subjects will
ingest 20 g of milk protein combined with 45 g of carbohydrate immediately
following 20 min of one-legged CWI of both legs at different temperatures
(i.e., 8 degrees Celsius vs. 30 degrees Celsius) or one-legged HWI of both legs
at different temperatures (i.e., 40 degrees Celsius vs. 30 degrees Celsius).
During the CWI period, a total of 7 resistance training bouts will be performed
separated by at least 1 recovery day. During the HWI period a single resistance
type exercise session will be performed. During the first training day of this
experiment, subjects will ingest 20 g of intrinsically [1-13C]-phenylalanine
and [1-13C]-leucine labeled milk protein [1, 2] combined with 45 g of
carbohydrate immediately following 20 min of one-legged cold or hot water
immersion (CWI/HWI). During this day, primed continuous intravenous tracer
infusions will be applied and regular blood samples will be collected to assess
digestion and absorption kinetics. Muscle biopsies will be obtained immediately
prior to beverage ingestion and 120 min and 300 min after beverage ingestion
from both legs to determine de novo muscle protein synthesis and glycogen
resynthesis rates from both cold water immersed (CWI) or hot water immersion
(HWI) and thermoneutral water immersed control (CON) legs. At the end of the
2-week training protocol, 2 additional muscle biopsies will be obtained (one
from the left leg and one from the right leg) to assess muscle protein
synthesis over 2 weeks in both legs.

The risks involved in participating in this experiment are minimal. Cold- or
hot-water immersion of the legs might give some temporal discomfort to the
subjects. Insertion of the catheters in a vein is comparable to a normal blood
draw and the risk is a small local hematoma. Blood samples will be drawn during
the screening and test day. In total, 16 blood samples of 8 mL and 8 muscle
biopsies will be obtained in the CWI trial. In the HWI trial, a total of 11
blood samples of 8 mL and 6 muscle biopsies will be obtained. The muscle biopsy
might cause some minor discomfort for maximally up to 24 h after the procedure,
characterized as a feeling that is comparable to muscle soreness or the pain
after bumping into a table. In addition, it might leave a dull feeling in the
muscle, which can take longer than 24 hours. The incision made for obtaining
the muscle biopsy will heal completely. The labeled, non-radioactive amino
acids tracers that will be infused intravenously are produced according to GMP
standards and are safe for human use. The subjects will ingest doses of 50ml of
70% deuterium oxide (2H2O) to enrich the body water pool to approximately 1 APE
(Atom Percent Excess). Deuterium oxide dosing to achieve a body water
enrichment of 1 APE is completely safe as it is far below the threshold for
biological toxicity in humans (approximately 20 APE) and will be returned to
baseline enrichments within 30 days. The test beverages used in the first
experimental test day contain intrinsically labeled dietary protein, which is
safe for human consumption and has been used in previous studies (MEC 12-3-058,
MEC 11-3-088 and MEC 14-3-002).