Running at Altitude: Why Sprinters Go Faster and Endurance Athletes Adapt

Why do people run faster at altitude?

While it may seem counterintuitive given the reduced oxygen availability, individuals can indeed run faster at altitude, particularly in sprint events, primarily due to the significant reduction in air density, which decreases aerodynamic drag.

The Altitude Paradox: What's Really Happening?

The notion that people run faster at altitude often sparks confusion. Common understanding suggests that the thinner air at higher elevations, with its lower partial pressure of oxygen, should impair athletic performance due to reduced oxygen uptake. This is largely true for endurance events. However, for short, high-intensity efforts like sprints, the physiological demands are different, and the altered atmospheric conditions can actually confer an advantage. The key lies in distinguishing between the acute effects of reduced air density and the chronic physiological adaptations that occur over time with altitude training.

The Science Behind Altitude Training: Acclimation vs. Acute Performance

When discussing performance at altitude, it's crucial to differentiate between two distinct scenarios:

• Acute Performance: This refers to an athlete's performance immediately upon arriving at altitude. For endurance events, performance is hindered due to hypoxia (reduced oxygen). For sprint events, performance can be enhanced due to reduced air resistance.
• Physiological Acclimation (Chronic Adaptation): This refers to the long-term changes the body undergoes when exposed to altitude for extended periods (weeks to months). These adaptations aim to improve oxygen delivery and utilization, which can then benefit endurance performance when returning to sea level.

This article focuses on the acute performance advantage for speed events.

The Role of Air Density

The primary reason for enhanced sprint performance at altitude is the reduction in air density.

• Less Air Resistance (Aerodynamic Drag): Air density decreases with increasing altitude because there are fewer air molecules per unit volume. For an athlete running at high speed, air resistance is a significant opposing force that must be overcome. This drag force is directly proportional to the air density, the square of the runner's velocity, and their frontal surface area.
• Reduced Drag Force: At an altitude of 2,000 meters (approx. 6,500 feet), air density is about 20% lower than at sea level. At 4,000 meters (approx. 13,000 feet), it's about 40% lower. This substantial reduction in air density translates to a proportional decrease in aerodynamic drag.
• Greater Net Forward Force: With less resistance to push against, the athlete's propulsive forces (generated by muscular contraction) result in a greater net forward force. This allows for higher top-end speeds and faster acceleration over short distances, even if oxygen delivery to muscles is slightly compromised. The energy saved from overcoming less air resistance outweighs the minor aerobic deficit for activities lasting only seconds.

Consider the 1968 Mexico City Olympics, held at an altitude of 2,240 meters (7,350 feet). This event saw numerous world records set in sprint and jumping events, largely attributed to the reduced air resistance.

Physiological Adaptations for Endurance (Why Training at Altitude Helps Later)

While reduced air density explains faster sprints at altitude, the long-term benefits of altitude training for endurance athletes returning to sea level are due to physiological adaptations:

• Increased Erythropoietin (EPO) Production: The kidneys detect the lower oxygen levels (hypoxia) and release more EPO, a hormone that stimulates red blood cell production in the bone marrow.
• Higher Red Blood Cell Count: More red blood cells mean a greater capacity to transport oxygen from the lungs to the working muscles.
• Enhanced Oxygen Utilization: The body also adapts by increasing mitochondrial density within muscle cells (where aerobic respiration occurs) and improving capillarization (the density of tiny blood vessels supplying muscles), both of which enhance oxygen delivery and utilization at the cellular level.
• Improved Buffering Capacity: Some adaptations may also improve the body's ability to buffer lactic acid, delaying fatigue.

These chronic adaptations are what make "Live High, Train Low" (living at altitude to gain physiological benefits, but training at lower altitudes to maintain high-intensity output) a popular strategy for endurance athletes. However, these are distinct from the acute air density effects relevant to sprint performance at altitude.

The Trade-Offs: Why Altitude Isn't Always Better

While sprints benefit from reduced air density, it's important to acknowledge that altitude presents significant challenges:

• Initial Performance Decrement: For endurance athletes, the immediate effect of altitude is a substantial drop in performance due to hypoxia. It takes weeks for the body to acclimate.
• Recovery Challenges: Recovery from intense training sessions can be slower at altitude due to reduced oxygen availability and increased physiological stress.
• Nutritional Needs: Athletes at altitude may have increased caloric and iron requirements to support red blood cell production and energy demands.
• Risk of Altitude Sickness: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE) are serious risks for unacclimated individuals ascending too quickly.

Practical Implications for Athletes

For competitive athletes, understanding the nuances of altitude performance is crucial:

• Sprinting Events: Athletes competing in sprint events (e.g., 100m, 200m, 400m, long jump, triple jump) at altitude can expect an advantage due to reduced air resistance. This is why some world records in these events have been set at altitude venues.
• Endurance Events: For endurance events (e.g., 5,000m, marathon), athletes will initially perform worse at altitude. Any benefit from altitude training for these events only manifests upon return to sea level, after sufficient time for physiological adaptations to occur.
• "Live High, Train Low" (LHTL): This strategy capitalizes on the benefits of altitude acclimation (increased red blood cells, etc.) while allowing athletes to perform high-intensity workouts at lower altitudes where oxygen is abundant, thus maintaining training intensity.

Conclusion

The phenomenon of faster running at altitude, particularly in sprint events, is a fascinating interplay of physics and physiology. While the reduced oxygen at higher elevations poses a challenge for aerobic metabolism and endurance, it simultaneously reduces the resistive force of air density. For events where aerodynamic drag is a significant factor and the duration is too short for oxygen deprivation to become a primary limiting factor, this reduction in air resistance provides a clear advantage, allowing athletes to achieve speeds unattainable at sea level. For endurance athletes, the benefits of altitude training are realized through chronic physiological adaptations that improve oxygen transport and utilization, which then enhance performance upon returning to lower elevations.