Oxygen is the most important nutrient during exercise, both at sea level and during high altitude training. As elevations increase, the oxygen available to the body decreases; for example, at 8,250 feet, about 27% less oxygen can enter the body than at sea level due to a drop in the partial pressure of oxygen, explains 2Peak. In order for triathletes to train under these conditions, their bodies must adapt and acclimatize to the lower oxygen levels available.
High Altitude and VO2Max
At higher altitudes, triathletes will notice that their breathing and heart rates are higher both at rest and during exercise. In addition, they are not able to reach their VO2max; typically, athletes experience a 2% drop in VO2max for every 1,000 feet above 5,000 feet, reports Trifuel. Given this, triathletes must pay close attention to the effects of high-altitude workouts. Close observation of perceived endurance helps triathletes avoid overtraining and injury, which they are more susceptible to during high altitude training.
High Altitude and Muscle Oxygen
Training with slight hypoxia (oxygen lack) should enable triathletes to develop a performance reserve by improving the delivery of oxygen to the muscles. However, some people are unresponsive to high altitude training. For example, triathletes who do not have adequate iron stores to begin with do not see an improvement in performance when practicing high altitude training. Ben Levine, MD, Professor of Medicine at the University of Texas Southwestern Medical Center, states that triathletes must have at least 30 ug/L of serum ferritin or the new red blood cells will have a low hemoglobin content and not be able to function properly. For this reason, the measuring of vascular oxygen transport capacity is essential to ensure that high altitude training is yielding the desired effects.
Similarly, triathletes with adequate iron stores may sometimes not benefit from high altitude training due to a slower and less sustained increased of erythropoietin (EPO), Levine explains. This can best be discovered by measuring muscle oxygen for its efficiency in transportation.
There are other effects that can cancel out the benefits of high altitude training for triathletes, such as an overly big increase in red blood cells. If the blood has too many red blood cells, it becomes too thick and oxygen transportation is impeded rather than increased. As Altitude.org points out, muscle oxygen measurement helps athletes determine whether they are receiving the benefits of high altitude training or in fact sacrificing their performance.