Ultramarathon Running: Pacing, Speeds, and Factors Influencing Performance

How fast do ultramarathoners run?

Ultramarathoners typically maintain a pace significantly slower than marathon runners, with speeds varying widely based on distance, terrain, and individual runner capabilities, often ranging from 7-12 minutes per mile (approximately 11-19 km/h) for shorter distances on flat terrain to walking pace on challenging trails.

Understanding Ultramarathon Pacing

Ultramarathon running, defined as any race longer than the traditional 26.2 miles (42.195 km) of a marathon, pushes the boundaries of human endurance. Unlike shorter races where athletes strive for maximal speed, ultramarathoners prioritize sustainable effort over extended periods. Therefore, "how fast" is a nuanced question, as the primary goal shifts from achieving a specific speed to successfully completing the immense distance, often under challenging conditions. Pacing in ultra-running is a complex interplay of physiological capacity, environmental factors, race strategy, and mental resilience.

Defining "Fast" in Ultramarathoning

The concept of "fast" in ultramarathoning differs dramatically from shorter-distance running. A 6-minute mile (3:45 min/km) pace, considered fast for a marathon, is virtually impossible to sustain for 50 or 100 miles. Instead, "fast" for an ultramarathoner means maintaining a consistent, metabolically efficient pace that minimizes fatigue and allows for continuous forward progress for many hours, or even days. This often involves strategic power hiking on inclines, brief walking breaks, and a highly disciplined approach to effort management.

Typical Pacing Ranges

Ultramarathon speeds are highly variable, influenced by factors such as distance, terrain, and the runner's experience level.

• 50-Kilometer (31-Mile) Races:
  • Elite Runners: May average 7-9 minutes per mile (4:20-5:35 min/km), finishing in 3.5 to 5 hours on flat courses.
  • Average Runners: Typically average 9-12 minutes per mile (5:35-7:30 min/km), completing the race in 5 to 7 hours.
• 50-Mile (80-Kilometer) Races:
  • Elite Runners: Pace slows to 8-10 minutes per mile (5:00-6:15 min/km), finishing in 6.5 to 8.5 hours.
  • Average Runners: Often average 12-15 minutes per mile (7:30-9:20 min/km), taking 10 to 12 hours or more.
• 100-Mile (160-Kilometer) Races:
  • Elite Runners: Pace can range from 9-12 minutes per mile (5:35-7:30 min/km) on flatter courses, finishing in 13 to 18 hours.
  • Average Runners: Pacing often drops to 15-25 minutes per mile (9:20-15:30 min/km), including significant walking, with finish times ranging from 20 to 30 hours, or even up to the maximum cutoff times (e.g., 36 hours).
• Multi-Day or Extremely Long Races (e.g., 200+ miles):
  • Pacing becomes even slower, often averaging 20-40 minutes per mile (12:30-25:00 min/km) or more, incorporating significant periods of power hiking and brief sleep breaks. These events are less about continuous running and more about sustained forward motion.

Key Factors Influencing Ultramarathon Speed

The speed an ultramarathoner can maintain is a function of numerous interconnected variables:

• Course Terrain and Elevation: Running on flat roads allows for faster paces than technical trails with significant elevation gain and loss. Steep climbs and descents necessitate power hiking or careful, slower running.
• Race Distance: As the distance increases, the average pace inevitably decreases. The physiological demands of sustained effort over many hours lead to progressive fatigue.
• Environmental Conditions: Heat, humidity, cold, wind, and altitude significantly impact performance. High temperatures demand slower paces to manage core body temperature, while extreme cold can impair muscle function.
• Runner's Experience and Training: A robust aerobic base, developed over years of consistent training, is crucial. Experience also brings improved pacing judgment, race strategy, and the ability to manage discomfort.
• Nutrition and Hydration Strategy: Effective fueling and electrolyte management are paramount. Inadequate intake leads to bonking (glycogen depletion) and dehydration, forcing a dramatic slowdown.
• Biomechanical Efficiency: An economical running form minimizes energy waste. Fatigue can degrade form, increasing energy expenditure and injury risk.
• Mental Fortitude: The ability to push through pain, maintain focus, and adapt to changing race conditions is critical. Mental strength often dictates whether a runner can maintain pace or is forced to slow down.
• Aid Station Strategy: Efficient transitions at aid stations, including refueling and resupplying, can save valuable time, while prolonged stops can significantly impact overall speed.

Pacing Strategies for Ultramarathons

Successful ultramarathoners employ sophisticated pacing strategies to manage their energy reserves:

• Start Slow: The most common advice is to start significantly slower than feels comfortable. This conserves glycogen stores and prevents early fatigue.
• Effort-Based Pacing: Instead of focusing on a specific mile pace, ultra-runners often use perceived exertion (RPE) or heart rate zones, adjusting pace based on terrain, fatigue, and environmental factors.
• Strategic Walking/Power Hiking: Integrating planned walk breaks, especially on ascents or after certain mile markers, is a common and effective strategy to conserve energy and reduce impact.
• Positive Splits: It is common and often necessary to run "positive splits" in ultras, meaning the second half of the race is slower than the first. The goal is to minimize the slowdown, not necessarily to negative split.
• Listening to Your Body: Adapting pace based on immediate physiological feedback – thirst, hunger, muscle fatigue, GI distress – is vital for long-term sustainability.

The Physiological Demands of Ultramarathon Pacing

The reason ultramarathoners run slower is rooted in fundamental exercise physiology:

• Energy System Contribution: While shorter races rely heavily on anaerobic glycolysis, ultras primarily depend on aerobic metabolism, burning fat and carbohydrates. Slower paces optimize fat oxidation, sparing precious glycogen stores.
• Muscle Fatigue: Repetitive eccentric contractions, especially on downhills, lead to significant muscle damage and fatigue, necessitating a slower pace to prevent injury and maintain function.
• Thermoregulation: Sustained effort generates heat. Slower paces reduce metabolic heat production, making it easier for the body to dissipate heat and prevent overheating.
• Nutrient Depletion and Absorption: The body can only absorb a finite amount of calories per hour. Slower paces reduce the energy deficit, making it easier to match energy expenditure with intake. Gastrointestinal issues are common at higher intensities.
• Central Nervous System (CNS) Fatigue: Prolonged physical and mental stress leads to CNS fatigue, which can reduce motor unit recruitment and perceived effort, making it harder to maintain a higher pace.

Conclusion

Ultramarathon running redefines "speed" from an absolute measure to a relative one, centered on efficiency, sustainability, and resilience. While elite athletes can maintain surprisingly fast paces for extended periods, the average ultramarathoner focuses on consistent, manageable effort, often incorporating strategic walking, to navigate immense distances and challenging terrain. The true measure of an ultramarathoner's "speed" lies not in their mile splits, but in their ability to maintain forward momentum and reach the finish line against formidable odds.