Running: The Flight Phase, Biomechanics, and Performance Optimization

Can you run with both feet off the ground?

Yes, absolutely. The presence of a "flight phase," where both feet are momentarily airborne, is the fundamental biomechanical characteristic that distinguishes running from walking and defines it as a distinct form of human locomotion.

The Defining Characteristic: The Flight Phase

Running is fundamentally defined by its gait cycle, which includes a crucial period known as the flight phase or non-support phase. During this brief but essential interval, neither foot is in contact with the ground. This airborne moment is what allows for the generation of greater speed and power compared to walking, where at least one foot, and often both, are always in contact with the ground (the "double support phase").

Biomechanics of the Running Gait Cycle

To understand the flight phase, it's helpful to break down the running gait into its primary components:

• Stance Phase (Support Phase): This is the period when one foot is in contact with the ground. It can be further divided:
  • Initial Contact: The foot first touches the ground (e.g., heel, midfoot, or forefoot strike).
  • Mid-Stance: The body passes directly over the supporting foot.
  • Terminal Stance (Propulsion/Toe-off): The foot pushes off the ground, generating the force needed for forward momentum and to initiate the flight phase.
• Swing Phase: This is the period when the foot is not in contact with the ground, moving forward to prepare for the next initial contact. It includes:
  • Initial Swing: The foot lifts off the ground.
  • Mid-Swing: The leg swings forward.
  • Terminal Swing: The leg extends, preparing for ground contact.

The flight phase occurs precisely between the terminal stance of one leg and the initial contact of the opposite leg. It is a transitional period where the body is propelled upwards and forwards, free from ground contact, before gravity inevitably brings the next foot down.

The Role of the Flight Phase in Running Performance

The flight phase is not merely an incidental outcome of running; it serves several critical functions:

• Energy Conservation and Recoil: During the powerful push-off of the stance phase, elastic energy is stored in tendons and muscles (e.g., Achilles tendon, plantar fascia). The flight phase allows this stored energy to be released efficiently, contributing to the next stride without constant muscular contraction.
• Increased Speed and Stride Length: Being airborne allows the runner to cover more ground with each stride. The greater the propulsive force at toe-off, the longer and higher the flight phase, directly correlating with increased running speed.
• Reduced Ground Contact Time: The flight phase inherently means less time spent absorbing impact forces, allowing the body to prepare for the next landing.
• Momentum Generation: The upward and forward trajectory during flight helps maintain momentum, making running a more continuous and fluid motion.

Anatomical and Physiological Underpinnings

Achieving and controlling the flight phase relies on a complex interplay of muscular strength, flexibility, and neuromuscular coordination:

• Powerful Propulsion: Muscles such as the gluteus maximus, hamstrings, and quadriceps are critical for generating the powerful hip and knee extension during terminal stance. The calf muscles (gastrocnemius and soleus) provide the final, explosive push-off from the ankle.
• Elasticity of Tissues: The tendons and fascia act like springs, storing and releasing elastic energy, particularly in the lower leg and foot. This passive recoil significantly contributes to the efficiency of the flight phase.
• Core Stability: A strong core (abdominals, obliques, erector spinae) is essential for maintaining an upright posture and transferring force efficiently from the lower body through the torso, preventing energy leaks and optimizing the propulsive forces.
• Neuromuscular Control: The brain and nervous system orchestrate the precise timing and intensity of muscle contractions needed for a coordinated push-off, controlled flight, and smooth landing.

Distinguishing Running from Other Locomotion

Understanding the flight phase clarifies the difference between running and other forms of human movement:

• Walking: Characterized by a continuous double support phase (both feet on the ground simultaneously for a brief period) and never a flight phase.
• Sprinting: An exaggerated form of running, featuring a much longer and more powerful flight phase due to maximal propulsive forces.
• Jumping: Involves a single, more sustained flight phase, typically initiated from a static or semi-static position, with a different trajectory and landing mechanics.

Optimizing Your Flight Phase

To enhance your running efficiency, speed, and reduce injury risk, focusing on the components that contribute to an effective flight phase is beneficial:

• Strength Training: Incorporate exercises that target the primary propulsion muscles:
  • Glutes and Hamstrings: Squats, deadlifts, lunges, glute bridges.
  • Quadriceps: Leg presses, step-ups.
  • Calves: Calf raises (seated and standing).
• Plyometrics: Exercises like box jumps, pogo jumps, and bounding drills improve elastic energy storage and release, directly enhancing your ability to generate a more powerful flight phase.
• Running Drills: Practice drills such as A-skips, B-skips, and high knees to improve hip drive, knee lift, and quick ground contact.
• Cadence and Stride Length: While a longer flight phase can increase speed, an appropriate cadence (steps per minute) is crucial for efficiency. Too long a stride can lead to overstriding and increased braking forces. Focus on powerful, efficient push-offs rather than simply trying to reach further.
• Posture: Maintain an upright posture with a slight forward lean from the ankles. This aligns your center of gravity for optimal forward propulsion and helps maximize the efficiency of your flight.

In conclusion, the ability to achieve a momentary state where both feet are off the ground is not just possible, but it is the very essence of running. By understanding and optimizing this biomechanical marvel, runners can unlock greater performance and move with enhanced efficiency and power.