High Altitude Training: Negative Effects, Risks, and Mitigation Strategies

What are the negative effects of high altitude training?

While high altitude training is often employed by endurance athletes to enhance performance, it presents a unique set of physiological stressors and potential health risks, ranging from acute altitude sickness to impaired training adaptation and increased risk of injury or illness.

Understanding the High-Altitude Environment

High altitude training involves exercising or living at elevations typically above 2,000 meters (approx. 6,500 feet) where the atmospheric pressure is lower, resulting in a reduced partial pressure of oxygen (hypoxia). While the body adapts by increasing red blood cell production and improving oxygen utilization, this adaptation process is demanding and can lead to several negative effects if not managed carefully.

Acute Physiological Responses and Altitude Sickness

The most immediate and well-known negative effects are related to the body's struggle to cope with the sudden lack of oxygen.

• Acute Mountain Sickness (AMS): This is the most common form of altitude sickness, typically occurring within 6-12 hours of ascending to high altitude. Symptoms include:
  • Headache
  • Nausea and vomiting
  • Dizziness and lightheadedness
  • Fatigue and weakness
  • Sleep disturbances
  • Loss of appetite AMS can severely impair training quality and general well-being, often requiring descent for recovery.
• High-Altitude Cerebral Edema (HACE): A severe and potentially fatal progression of AMS, HACE involves swelling of the brain. Symptoms include:
  • Severe headache unresponsive to medication
  • Ataxia (loss of coordination, difficulty walking in a straight line)
  • Confusion and altered mental status
  • Hallucinations
  • Coma HACE is a medical emergency requiring immediate descent and medical attention.
• High-Altitude Pulmonary Edema (HAPE): Another life-threatening condition, HAPE is characterized by fluid accumulation in the lungs, making breathing extremely difficult. Symptoms include:
  • Extreme shortness of breath at rest
  • Persistent cough, often producing frothy sputum
  • Chest tightness or congestion
  • Rapid heart rate and breathing
  • Cyanosis (bluish discoloration of lips/nails) Like HACE, HAPE is a medical emergency requiring immediate descent and medical intervention.
• Sleep Disturbances: Hypoxia often disrupts normal sleep patterns, leading to fragmented sleep, frequent awakenings, and periodic breathing (Cheyne-Stokes respiration). Poor sleep impairs recovery, cognitive function, and overall mood, directly impacting training effectiveness.

Detrimental Effects on Training and Performance

Even without full-blown altitude sickness, the hypoxic environment significantly alters training capacity and recovery.

• Reduced Training Intensity and Volume: Athletes cannot perform at the same intensity or volume at altitude as they can at sea level. This means:
  • Lower absolute power output: Strength and power activities are particularly affected due to the reduced oxygen availability for high-intensity, anaerobic efforts and the overall physiological stress.
  • Slower running/cycling speeds: Endurance performance is compromised.
  • Difficulty maintaining typical training loads: This can lead to de-training effects in specific high-intensity domains if not carefully managed.
• Slower Recovery: The body is under constant stress at altitude, leading to:
  • Increased sympathetic nervous system activity: Elevates heart rate and blood pressure.
  • Higher metabolic rate: The body works harder just to maintain basic functions.
  • Impaired immune function: Increased susceptibility to illness. All these factors contribute to slower recovery from training sessions, increasing the risk of overtraining.
• Increased Risk of Overtraining: The cumulative stress of hypoxia, combined with training, can push athletes into an overtrained state more easily than at sea level. Symptoms include persistent fatigue, performance plateaus or decline, mood disturbances, and increased susceptibility to illness.
• Loss of Muscle Mass (Catabolism): The hypoxic environment can induce a catabolic state, meaning the body breaks down muscle tissue for energy. This is often linked to:
  • Increased cortisol levels: A stress hormone that promotes muscle breakdown.
  • Reduced appetite: Leading to insufficient caloric intake.
  • Increased energy expenditure: The body burns more calories at rest. This can be particularly detrimental for athletes focused on strength, power, or maintaining lean body mass.
• Dehydration Risk: Altitude increases respiratory rate, leading to greater insensible water loss through breathing. The dry air also contributes to fluid loss. Dehydration can exacerbate symptoms of altitude sickness and impair performance.

Metabolic and Nutritional Challenges

High altitude significantly impacts metabolism and nutritional requirements.

• Increased Energy Expenditure: The body expends more energy at rest and during exercise at altitude due to the increased work of breathing, thermoregulation, and metabolic adaptations. This means higher caloric needs that must be met.
• Appetite Suppression: Paradoxically, many individuals experience a significant decrease in appetite at altitude, making it difficult to consume enough calories to meet increased demands. This can lead to unintended weight loss and muscle catabolism.
• Iron Deficiency Anemia: While altitude stimulates red blood cell production, this process requires adequate iron. If iron intake is insufficient, or if there's increased iron loss (e.g., through exercise-induced hemolysis), athletes can develop iron deficiency anemia, which counteracts the benefits of altitude training and impairs oxygen transport.

Psychological and Cognitive Impacts

The challenges of high altitude training extend beyond the physical realm.

• Mood Disturbances: Athletes may experience increased irritability, anxiety, depression, and difficulty concentrating due to hypoxia, sleep deprivation, and the overall stress of the environment.
• Cognitive Impairment: Decision-making, reaction time, and complex problem-solving abilities can be temporarily impaired at altitude, which can affect training execution and safety.

Practical Considerations and Mitigation Strategies

While the focus here is on negative effects, understanding how to mitigate them is crucial for anyone considering high altitude training.

• Gradual Acclimatization: The most critical step to minimize negative effects is a slow, progressive ascent, allowing the body time to adapt.
• Hydration and Nutrition: Maintaining adequate fluid intake and ensuring sufficient caloric and iron-rich nutrition are paramount.
• Monitoring and Adjustment: Closely monitoring symptoms, adjusting training loads, and prioritizing rest are essential.
• Medical Consultation: Individuals with pre-existing health conditions (e.g., cardiovascular, respiratory, or hematological issues) should consult a physician specializing in altitude medicine before undertaking high altitude training.

Conclusion

High altitude training, while a powerful tool for physiological adaptation and performance enhancement in specific contexts, is not without its significant drawbacks. From acute and potentially life-threatening altitude sickness to chronic impairments in training capacity, recovery, and overall well-being, the hypoxic environment demands respect and careful management. Athletes and coaches considering this training modality must weigh the potential benefits against these considerable risks, prioritizing health, safety, and a meticulously planned acclimatization and training strategy.