Feet During the Gait (Walking) Cycle.

The gait cycle refers to the sequence of events that occur from the initial contact of one foot with the ground to the point when the same foot contacts the ground again. The gait (walking) cycle is divided into different phases, each with distinct foot functions. Understanding these phases provides insights into the complex biomechanics of walking. The main phases of the gait cycle are:

Walking Cycle

1. Stance Phase:

• Heel Strike (Initial Contact): The gait cycle begins with the heel strike of the foot, where the heel makes initial contact with the ground. The foot is in a dorsiflexed position, and the ankle absorbs the shock of the impact. The round surface of the heel (tuber) acts as a fulcrum for the foot to roll until the foot is flat on the ground.

• Foot Flat (Loading Response): The foot progresses to a flat position as the body weight begins to transfer over the foot. The foot begins pronating slightly unlocking the mid foot and allowing for shock absorption. This pronation also causes the foot to flatten, putting stretching on the plantar ligaments, such as the plantar fascia, storing elastic energy for later use.

• Midstance: The foot is planted and stable, allowing for the body to travel over it. The ankle passively dorsiflexes as the body moves over the foot until the maximum range of dorsiflexion is achieved. (Note - this should be at least 10 degrees beyond neutral for proper function). The arch of the foot continues to act as a shock absorber, helping to dissipate forces generated during walking and charging the plantar ligaments.

• Heel Lift (Terminal Stance): Once the ankle is in full dorsiflexion, the heel begins to lift off the ground as the body weight moves forward over the ball of the foot. The plantar ligaments elastically contract, aiding in supination of the foot. When the foot is in a supinated position, the midfoot locks and allows the foot to act like a rigid lever to push off from.

• Toe-Off: The foot pushes off the ground with the toes, propelling the body forward. The ankle and big toe joint actively plantar flex the foot, creating propulsion all the way through until the big toes leave the ground, initiating the next phase.
  

2. Swing Phase:

• Initial Swing: The weight is fully transferred to the opposite limb, and the foot begins to swing forward as the knee flexes to lift the foot off the ground.

• Mid-Swing: The foot continues to swing forward, clearing the ground. The ankle actively dorsiflexes to remain in a dorsiflexed position and ensure that the toes clear the ground.

• Terminal Swing: The leg extends as the foot prepares for the next heel strike with a slightly dorsiflexed ankle.
  

Key Functions of the Foot during Gait:

1. Shock Absorption: During heel strike and foot flat, the foot functions as a shock absorber, dissipating the impact forces generated by walking.

2. Weight Distribution: The foot distributes body weight evenly during the stance phase, ensuring stability and balance.

3. Propulsion: During toe-off, the foot provides propulsion by pushing off the ground, allowing forward movement.

4. Adaptation to Terrain: The foot adapts to changes in terrain by adjusting its position and arch height, ensuring stability on uneven surfaces.

5. Energy Conservation: The foot contributes to energy conservation by converting potential energy into kinetic energy during the gait cycle.

6. Dynamic Stability: The foot maintains dynamic stability throughout the gait cycle, preventing excessive pronation or supination.
   

Understanding the foot's role in each phase of the gait cycle is essential for diagnosing and treating gait abnormalities or conditions affecting the lower extremities. Podiatrists and physical therapists may analyze gait patterns to identify issues and recommend interventions such as orthotics, footwear modifications, or gait training exercises to optimize foot function and overall biomechanics during walking. It is important to remember that muscle imbalances, such as a tight calf muscle (equinus) leads to excessive pronation, which interferes with proper foot function during gait.

Running

So running is just a faster version of walking, correct? Well no. While walking is smooth and focuses on efficient locomotion and conservation of energy, running is more like controlled bouncing or falling. When the main goal is speed, you have to start making trade-offs. As you speed the walking cycle, you retain essentially all of the same phases of gait previously mentioned. However, you will find that you will reach a maximum speed quickly. Not only that, but it also causes your muscles to have to work harder to maintain all of those individual phases. This is one of the reasons why "power walking" is considered a workout. As you transition to jogging, you will see less and less time spent in heel contact until you skip over this step entirely, causing you to land on a flat foot. About the time this happens, a new phase is introduced called the "float" phase. This phase is defined as the time when neither limb is touching the ground. This differs significantly from the walking cycle, which alternates between single and double limb support. The running cycle, on the other hand, cycles between single limb support and float phases. See what I mean by bouncing? The stride distance increases, and the base of gait (side-to-side distance between the two feet) becomes narrower. As the cadence increases, less and less of the original cycle remains as the weight shifts further and further forward in the foot. When sprinting, there is no longer a mid-foot stand phase, and instead, the ball of the foot is the only part of the foot that comes into contact with the ground. The stride distance further increases, and the base of gait further narrows until it is almost a straight line.