Why does exercising at high altitude make you feel like you're out of shape?

Have you ever tried running or hiking up a mountain and feeling like you can’t breathe? Training or competing above sea level is already physically demanding, but exposure to altitude further increases our fatigue. However, if we take advantage of training at high elevations, exercising will feel a lot easier as it promotes our physiological adaptations to environmental stressors. 

Figure 1: Man training at high altitude

Why does high altitude make it harder to exercise?

This is a training technique where athletes train at high elevations, typically at least 3000-5000m above sea level. At this altitude, there are fewer oxygen molecules in the air, meaning that we have a lower partial pressure of oxygen (PO₂) exerted on our bodies (Nunez, 2020). As a result, the decreased air density and PO₂ lead to hypoxia, a condition in which our body’s blood and cells receive insufficient oxygen. Exercising will feel more challenging, and we get fatigued more easily. Hence, the idea of high altitude training is to let our bodies adapt to the lack of oxygen levels, which could significantly improve our performance at both sea level and altitude.

Body responses to altitude

Our cardiovascular, respiratory, and metabolic systems make significant adaptations in response to high altitude. With constant exposure to altitude, our bodies acclimatise to the environment naturally, which leads to enhanced oxygen delivery and consequently improves sports performance (Skratchlabs, 2024).

Immediate effects

• ↑ risk of altitude sickness (headache, nausea, etc)

• ↑ frequency of breaths

• ↑ heart rate and ventilation

• ↑ difficulty sleeping

• ↑ dehydration risk

• ↓ appetite -> weight loss

• ↓ plasma volume 

Long-term adaptations/benefits

• ↑ red blood cell production

• ↑ haemoglobin concentration, blood/plasma volume

• ↑ oxygen-carrying capacity to muscles

• ↑ VO2 max (aerobic capacity)

• ↑ metabolic rate

• ↓ resting heart rate

“Live High, Train Low” (LHTL) concept

Figure 2: LHTL approach (left: living at altitude, right: training at sea-level)

This training approach is one of the popular methods of high altitude training. It involves living at high altitude but doing intensive training at low altitudes to maximise physiological adaptations (Nunez, 2020).  

Ways to prepare your body for high altitude training

1. Gradually increase elevation and exercise intensity/duration

   1. It is recommended to plan 2-3 rest days when acclimatising to lower oxygen levels

2. Stay hydrated and maintain adequate fuel (iron) intake

3. Check with a doctor before starting this training program

4. Take altitude sickness medications (if necessary): to reduce altitude sickness symptoms

5. Prioritise sleep and recovery

6. Practice breathing techniques

Conclusion

In essence, altitude training has been shown to enhance exercise endurance by increasing our oxygen delivery to working muscles and improving overall aerobic capacity. With the right approach to this type of training technique, athletes can enhance their performance and better prepare their bodies for competition.

Reference List

Nunez, K. (2020). Altitude Training: Does It Work and How to Do. [online] Healthline. Available at: https://www.healthline.com/health/altitude-training#takeaway [Accessed 23 Aug. 2025].

Skratchlabs (2024). Altitude and Athletic Performance: Why It Hurts, Helps, and How to Tra. [online] Skratchlabs. Available at: https://www.skratchlabs.com/blogs/blog/altitude-and-athletic-performance-why-it-hurts-helps-and-how-to-train-for-it [Accessed 23 Aug. 2025].