2 Phases Of Running Gait Cycle

Running can be understood by using an analysis of the gait cycle. Unlike walking, which is defined by having both feet simultaneously in contact with the ground during a cycle, running is characterized by having both feet off the ground during a cycle (a cycle is defined as the period between when one foot makes initial contact with the ground until the same foot reconnects with the ground). 

The two phases of the gait cycle are the stance, or support,phase and the swing phase. When one leg is in the stance phase, the other is in the swing phase.The stance phase is marked by the foot’s initial contact with the ground (foot strike), mid  stance through toe-off and takeoff. 

This phase has been measured at approximately 40 percent of the gait cycle; however, for elite distance runners and sprinters it represents considerably less of the total phase. 

The swing phase begins with the float, which morphs into the forward swing or swing reversal, and finishes with the landing or absorption, which begins the next cycle. The right leg is in the stance phase (making contact with the ground), and the left leg is in the swing phase, preparing to make contact with the ground.

A.Stance Phase  

The quadriceps group, specifically the rectus femoris , is heavily active before initial contact. Once contact is made, the muscles, tendons, bones, and joints of the foot and lower leg function to dissipate the impact of the landing. Specifically, three related but separate foot movements occur. The subtalar joint inverts and everts, the midfoot abducts or adducts,and the forefoot dorsiflexes and plantarflexes. Ideally, through this interaction of the anatomy of the lower leg, a small amount of pronation, the inward collapsing of the rear foot, occurs. This pronation helps dissipate the shock of the landing by spreading the impact over the full surface of the foot at midstance. 

An under pronated foot at midstance is less prepared to cushion the impact of  landing because only the lateral aspect of the foot is in contact with the ground.This type of biomechanics can lead to chronically tight Achilles tendons, posterior calf strains, lateral knee pain, and iliotibial band tightness . 

Conversely, an over pronated foot at midstance can result in tibia pain, anterior calf injuries, and medial-side knee pain because of the internal rotation of the tibia. 

Neither extreme, a high rigid arch that under pronates or supinates or a low hypermobile arch, is ideal. Mild to moderate pronation  is normal and very effective at combating impact stress.

B.Swing Phase

After the initial contact and midstance positioning, the hamstrings and hip flexors, the quadriceps, and the muscles of the calf ( gastrocnemius and soleus)work in conjunction to allow a proper takeoff. While one leg is moving through its gait cycle, the other leg is preparing to begin a cycle of its own. 

Having already contacted the ground, this leg begins its forward motion as a result of the forward rotation of the pelvis and the concurrent hip flexion caused by the psoas muscles. As the leg passes through the forward swing phase, the hamstrings lengthen, limiting the forward extension of the lower leg, which had been extended by the quadriceps. 

The lower leg and foot begin to descend to the running surface as the torso accelerates, creating a vertical line from head to toe upon impact.Note that two cycles, one by each leg, are happening simultaneously. As one foot takes off the ground to begin its swing phase, the other leg is preparing to begin its stance phase. 

The dynamic nature of the running movement makes isolating the anatomy involved difficult because, unlike in walking, potential energy (the energy stored within a physical system) and kinetic energy (the energy of a body resulting from its motion) are simultaneous. 

Essentially, the anatomy involved in running is constantly turned on both as agonists, muscles that are prime movers, and antagonists, muscles with opposing or stabilizing motion. In walking, the muscles are either one or the other during the gait cycle.

The role of the core during the stance phase is identical to its role in the swing phase, providing stability for the upper body, which allows the pelvis to twist and rotate in its normal manner. Because the gait cycle is defined by each leg moving through the stance or swing phase simultaneously, stabilizing the pelvis so it can function appropriately is an important task.