Running Speed: Definition, Thresholds, Training Zones, and Influencing Factors

What speed is running?

Running is fundamentally defined by a distinct gait cycle that includes a momentary "flight phase" where both feet are simultaneously off the ground, a key biomechanical differentiator from walking. This transition typically occurs at speeds exceeding a certain individual threshold, often around 4-5 mph (6.5-8 km/h), but encompasses a broad range from slow jogging to maximal sprinting.

Defining Running: The Gait Cycle Perspective

From a biomechanical standpoint, the primary characteristic that differentiates running from walking is the gait cycle. While walking involves a continuous contact with the ground, with at least one foot always in contact, running introduces a "flight phase" or "non-support phase." During this brief period, both feet are airborne. This aerial phase is what allows for greater ground reaction forces and, consequently, higher speeds.

The running gait cycle involves:

• Stance Phase: When the foot is in contact with the ground, absorbing impact and propelling the body forward.
• Swing Phase: When the foot is off the ground and moving forward to prepare for the next contact.
• Flight Phase: The unique period in running where neither foot is in contact with the ground.

This biomechanical shift necessitates greater muscle activation, higher energy expenditure, and increased cardiovascular demand compared to walking at similar perceived effort levels.

The Speed Threshold: When Walking Becomes Running

There isn't a single, universally fixed speed at which walking definitively transitions into running, as it can vary based on individual biomechanics, leg length, fitness level, and even perceived effort. However, scientific observations and practical experience point to a general range for the walk-run transition speed:

• Typical Range: For most adults, this transition commonly occurs between 4 to 5 mph (approximately 6.5 to 8 km/h). Below this range, most individuals find it more efficient to walk; above it, running becomes the more natural and energy-efficient mode of locomotion.
• Individual Variability: Taller individuals with longer legs may find their walk-run transition speed to be slightly higher, while shorter individuals might transition at a lower speed. Factors like fatigue, terrain, and carrying external loads can also influence this threshold.
• Metabolic Efficiency: Research indicates that the body naturally opts for the most metabolically efficient gait. As speed increases, the energy cost of walking eventually surpasses that of running, prompting the transition.

Range of Running Speeds: From Jogging to Sprinting

Once the flight phase is established, the "speed of running" becomes a spectrum, categorized by intensity and physiological demand:

• Jogging (Slow Running):
  • Speed: Typically ranges from 4-6 mph (6.5-10 km/h).
  • Characteristics: A comfortable, conversational pace where the primary energy system is aerobic. It's sustainable for longer durations and often used for warm-ups, cool-downs, or recovery runs.
• Moderate/Tempo Running:
  • Speed: Generally 6-8 mph (10-13 km/h), though highly dependent on individual fitness.
  • Characteristics: A challenging but sustainable pace, often at or near the individual's lactate threshold. Conversation becomes difficult, indicating a higher intensity aerobic effort. Used for building endurance and improving aerobic power.
• Fast Running/Threshold Running:
  • Speed: 8-10 mph (13-16 km/h) or faster, pushing beyond tempo pace.
  • Characteristics: A significant aerobic challenge, often at or slightly above lactate threshold, verging into anaerobic contribution. Sustainable for shorter durations (e.g., 20-60 minutes).
• Sprinting (Maximal Effort Running):
  • Speed: Highly variable, from 10 mph (16 km/h) up to 20-28 mph (32-45 km/h) for elite athletes.
  • Characteristics: Maximum effort, primarily utilizing anaerobic energy systems. Sustainable only for very short bursts (seconds to less than 2 minutes). Requires high levels of power, strength, and explosive force.

Factors Influencing Running Speed

An individual's running speed is a complex interplay of physiological, biomechanical, and external factors:

Physiological Factors:

• VO2 Max: The maximum rate at which the body can consume and utilize oxygen during intense exercise. A higher VO2 max generally correlates with greater aerobic capacity and potential for sustained speed.
• Lactate Threshold: The highest exercise intensity or speed that can be maintained without a rapid accumulation of lactate in the blood. Training to improve this threshold allows for faster running over longer distances.
• Muscle Fiber Type: A higher proportion of fast-twitch muscle fibers contributes to explosive power and speed (essential for sprinting), while slow-twitch fibers are crucial for endurance and sustained slower running.
• Cardiovascular Efficiency: The heart's ability to pump oxygenated blood to working muscles, and the muscles' ability to extract that oxygen.
• Mitochondrial Density: The number of mitochondria within muscle cells, which are the "powerhouses" for aerobic energy production.

Biomechanical Factors:

• Stride Length: The distance covered with each step.
• Stride Frequency (Cadence): The number of steps taken per minute. Optimal speed often results from a balance between stride length and frequency.
• Running Economy: The amount of oxygen consumed at a given running speed. A more economical runner uses less oxygen to maintain the same pace, indicating greater efficiency.
• Running Form/Technique: Efficient mechanics minimize wasted energy and optimize propulsion.

External Factors:

• Terrain: Running uphill or on soft surfaces (sand, grass) significantly reduces speed compared to flat, firm ground.
• Elevation: High altitude reduces oxygen availability, impacting speed.
• Weather Conditions: Headwinds, extreme heat, or cold can decrease performance and speed.
• Footwear: Appropriate running shoes can optimize comfort, support, and energy return.

Training & Experience:

• Specificity of Training: Training at specific speeds and intensities (e.g., interval training, tempo runs) directly improves performance at those speeds.
• Strength Training: Building leg and core strength improves power output and reduces injury risk, indirectly boosting speed.
• Consistency: Regular training adaptations lead to long-term improvements in all contributing factors.

Measuring and Tracking Running Speed

Running speed can be measured in several ways:

• Pace: This is the most common metric for runners, expressed as time per unit distance (e.g., minutes per mile or minutes per kilometer). A lower pace indicates faster running.
• Speed: Expressed as distance per unit time (e.g., miles per hour or kilometers per hour).
• Tools: GPS watches, smartphone apps, treadmills, and track measurements are used to accurately track and display running speed and pace.

Monitoring these metrics is crucial for:

• Performance Tracking: Assessing progress and setting new goals.
• Training Prescription: Ensuring workouts are performed at the correct intensity.
• Race Strategy: Pacing oneself effectively during competitions.

The Significance of Running Speed for Health and Performance

Understanding "what speed is running" and the factors influencing it is vital for both general health and athletic performance:

• Cardiovascular Health: Running at various speeds, particularly within the moderate to high-intensity zones, significantly improves cardiovascular fitness, lowers blood pressure, and reduces the risk of heart disease.
• Bone Density: The impact forces associated with running stimulate bone remodeling, leading to stronger bones. Higher speeds generally produce greater forces, potentially offering more significant benefits.
• Weight Management: Running is an effective way to burn calories. Higher speeds increase caloric expenditure per unit of time, aiding in weight loss or maintenance.
• Performance Goals: For competitive runners or those aiming for personal bests, manipulating running speed through structured training is the direct path to improvement. This involves integrating speed work, tempo runs, and long, slow distances.
• Injury Prevention: While faster running can be beneficial, increasing speed too rapidly without adequate preparation can elevate the risk of overuse injuries. A progressive approach to increasing both mileage and speed is essential.

In conclusion, running speed is not a single value but a continuum, defined by a unique biomechanical gait and influenced by a myriad of physiological and external factors. Understanding these elements empowers individuals to train more effectively, optimize their performance, and harness the full range of health benefits that running offers.