High Altitude Training - Principles and concepts to know

 Being a sea-level residents, we may have done high altitude activity at least once in a life time, whether it is a well structured protocol or just guided hiking. Every time we do activity in high altitude it is always tougher for us than in sea-level. If you have questions on why it is difficult to do activities in high altitude than sea-level? Then this post is for you. There is no doubt we have tons of training related questions at high altitude. Here i come up with few questions with an appropriate concepts and principles. Here we go.

1. Why performances are actually expected to be better because they were conducted at high altitude?

Basically, It all starts from the change in atmospheric (or) barometric pressure. Atmospheric pressure is a measure of the weight of the column of air directly over the any spot on the earth. At sea level weight of the column is greatest. 

"As one climb higher and higher then the weight column is reduced. Consequently atmospheric pressure is reduced with increasing in altitude. The air is less dense. The change in partial pressure of the atmospheric gas is solely due to change in atmospheric pressure"

The decrease in partial pressure of oxygen (PO2) at high altitude has direct effect on oxyhemoglobin saturation (HbO2). This condition is called hypoxia. 

But how do these changes occurs?

To answer these question, we can divide into anaerobic performance and aerobic performance

Anaerobic performance: 

For anaerobic training (training with absence of oxygen) has ATP, PCr and glycolytic pathway as a predominant source of energy and the anaerobic exercises lasting for two mins or less without oxygen. if this statement is correct then anaerobic training shouldn't be affected by low PO2 at altitude because Oxygen transport to the muscle is not limiting performance.

"The anaerobic performance increases at high altitude training because the density of the air is less resistance to movement at high speeds. So high speed movements and sprint performance are not affected and are improved"

Aerobic Performance:

For aerobic training (training with the presence of oxygen) are primarily dependent on oxygen delivery and its clearly aerobic performance is affected by lower partial pressure of oxygen at altitude. 

Here a question arises, 

2. Did the athlete born and raised at high altitude possess a special adaptations due to their birthplace?

The following are the possible mechanisms,

• Low partial pressure of oxygen at high altitude triggers hypoxia inducible factor-I (HIF-I) present in most cells of the body. This hypoxia inducible factor-I activates genes associated with erythropoitin (EPO) production that is involved in Red Blood Cells (RBC) production.
• Vascular endothelial growth factors that are involved in generation of new blood vessels and nitric oxide synthase that promotes the synthesis of nitric oxide that involved in vasodilation.

"In high altitude populations the acclimatization responses is to produce additional red blood cells to compensate for desaturation of hemoglobin. Usually high altitude population have more red blood cells than people in sea-level, More hemoglobin means more oxygen transport which increases the maximal oxygen consumption. Any sea-level residents who makes a journey to high altitude and stays a while will experience a acclimatization responses that involves increases in red blood cells but not completely as permanent residents"

3. Why it is difficult to maintain a  body weight at the high altitude?

Prolonged high altitude exposure reduces lean body mass (Muscle fiber atrophy) and body fat with the magnitude of weight loss directly related to elevation. This results from a reduced energy intake at altitude, In addition to that the efficiency of intestinal absorption decreases. These combination makes one to maintain body weight at the high altitude.

4. What happens to VO2 max at high altitude?

 Cardiovascular function at altitude:

Remember fick's equation,

VO2max = Cardiac output * a-vo2 (arteriovenous oxygen difference)

Decrease in VO2max with high altitude could be due to decrease in cardiac output and oxygen extraction.

As we know that maximum heart rate cannot be changed with training even in the high altitude. So it clear to know that 

• Decrease in stroke volume is the reason for reduction of maximal oxygen consumption. 
• Decrease in oxygen extraction due to decrease in arterial oxygen content (CaO2) and increase in mixed venous oxygen content (CvO2). 
• It happens due to low partial pressure of oxygen--->Low oxyhemoglobin--->Low alveolar partial pressure of oxygen---> Low pressure for oxygen  diffusion between alveolus and pulmonary capillary blood--->transport of oxygen to the muscle is reduced due to desaturation---> Low VO2 max

Respiratory Function at high altitude:

At altitude, air is less dense. This means fewer oxygen molecules per litre of air and if the person wanted to consume the same amount of the oxygen then the pulmonary ventilation would have to increase. For instance, If the amount of oxygen molecules present in the atmosphere is reduced by one-half then the person would have to breathe twice as much air to take in the same amount of the oxygen. In order consume the same amount of oxygen in the high altitude the primary respiratory muscle diaphragm have to  work hard that fatigue may occur

Keep in mind:

At high altitude, Each litre of blood carries low oxygen so more litres of blood must be pumped out from the heart per minute. In order to compensate heart rate is increased. To maintain target heart rate zone, person who participates in an exercise program will have to decrease the intensity of exercise and also achieve proper caloric expenditure and the duration of the training need to be properly prescribed. Before planning an exercise program at high altitude consider all the factors (sleeping quality, recovery zone, medications (drug-drug interactions), supplementation and so on...)

In the bottom line,

• Partial pressure of oxygen at high altitude is less. It leads to changes in physiological functions. Based on the activity duration the effects may differ. Anaerobic training at high altitude may increase the performance as the less dense air is less resistance to high speed movement, so the person may break their personal record in sea-level. Aerobic training requires oxygen it can be negatively affected by high altitude.
• Native high altitude population who were born and raised there, has more red blood cells than sea-level residents. It makes them to have increased oxygen transport and they have a complete acclimatization to high altitude.