Endurance exercise at high altitude under carbohydrate supplementation

Many athletes, especially cyclists like to train at high altitude to achieve
training stimuli that cannot be generated at sea level. The energy production
of the muscle depends more on anaerobic metabolism during high altitude
conditions. This means that the (an)aerobic power of the body can be trained at
a lower submaximal training intensity. The necessary shift from aerobic to
anaerobic energy production, leads to a selective use of carbohydrates. The
nutritional advice for cyclists wanting the best possible performance at high
altitude needs to be adjusted to the higher use of carbohydrates. Sport
dietitians prefer customized nutritional advice.

Insight in the relative and absolute contribution of substrates during exercise
contributes to an adequate nutritional strategy advised by sport dietitians for
athletes who are acutely exposed to high altitude conditions. An adequate
nutritional strategy can improve physical performance of athletes acutely
exposed to high altitude conditions. The increase of oxygen consumption by
increasing work load with 25 Watt are indicative for changes in energy
production of the muscle.

Randomised controlled single blind crossover design

In this study with high altitude simulation cyclists perform an incremental
exercise protocol 3 times (A, B, C). The only difference between the 3
protocols is the simulated altitude (sea level or 2500 m) and following the
nutritional guidelines (350 ml isotonic sports drink) for endurance athletes:

Protocol A: Sea level 0 m 21% O2 - no
nutritional intervention
Protocol B: High altitude 2500 m 16% O2 - no nutritional intervention
Protocol C: High altitude 2500 m 16% O2 - carbohydrate supplementation

Because the subjects are well trained, the exercise protocol starts at a
relative high work load of 100 Watt. The work load will be increased with 25
Watt each 5 minutes to a maximal work load of 300 Watt.

Although each of the exercise protocols is designed to end with heavy exertion,
the exercise protocol cannot be considered as potentialle dangerous or riskful
for the (semi)-professional riders who participate in this study. The work load
during the exercise protocols does not exceed the work load of semi
professional cyclists during training. The work load of semi professional
cyclists during training is often higher. During the study exercise protocols
are stopped by the researcher when the heart rate exceeds 90% of the maximal
heart rate (HRmax). The HRmax is individually determined by the sports
phycisian. During competition such as time trials semi professional cyclists
ofte exceed a exercise intensity 90% HRmax.