What Is The Gait Cycle?
The gait cycle is the technical name for how we walk. Walking is so fundamental to our daily activities that we often it for granted. But walking, or gait, requires a complex series of actions. Many books have been written on the gait cycle and the nitty gritty details are beyond the scope of this article. But it can be helpful to our understanding of how we do any kind of functional movement to take a look at how we walk. So, in this article, I’ll give you a broad overview of what happens when we walk.
Breaking down the gait cycle
A gait cycle, also called a “full stride,” is composed of taking one step with each foot. It’s broken down into two main pieces. We are in the “stance” period when our striding food is connected with the ground. The "swing" period occurs when that foot is in the air. The brief moment when both feet are touching the ground is called the "double limb support" phase.
Each of those subsections of a gait cycle can be broken down further. The stance phase begins with heel strike, then continues with weight-acceptance, followed by a mid-stance and then a late-stance phase. We spend about 60% of our gait cycle in the stance period. The swing period starts with toe-off and then continues through early swing, mid-swing, and late swing. We spend about 40% of our gait cycle in the swing phase.
Let’s take a walk through the gait cycle to learn more about what happens during each of these phases.
Taking a walk
A gait cycle technically begins with the heel strike. That’s the moment that the heel of our front foot meets the ground after we’ve swung that foot through. Then we shift our weight onto that leg (the weight-acceptance phase) and roll through our foot as we shift our body weight forward to complete the mid- and late-stance phases. During these portions of the stance phase, we pick our heel up and then our mid-foot as we shift our weight forward and roll through our foot.
The momentum of our body going forward then brings us to toe-off on that same foot. That’s the moment that we lift our toes off the ground and our foot is in the air. We then swing that leg forward through the early, mid-, and late-swing phases to arrive back at heel strike when the heel of that same foot meets the ground again.
Why is gait more complex than static posture?
There are many forces that influence how we walk (and move in other ways too) that are less involved with maintaining our static posture. While gravity is active in both cases of course, during movement we also interact with momentum and something called the ground force reaction. This is the force created by the ground in response to our body contacting it. So, for example, when our foot hits the ground at heel strike, there is a force going down through our body into the ground created by our movement, and there is a reciprocal force that is generated by the ground in response that moves back up into our body.
Additionally, we have skeletal, muscular, and fascial (connective tissue) components that all come together to support a healthy gait. The ideal gait involves our whole body. While we might think of walking as something that mostly happens in our lower body, that isn’t really true. In fact, the more we involve the whole body, the more we can rely on the fascial spring loading of winding and unwinding, and the less muscular effort is necessary. In every plane, our body is pre-tensioning and then using that kinetic energy to move us forward.
What is the body doing when we walk?
Sagittal plane movement
Our body is moving three-dimensionally, of course when we move. This also makes it more complicated to describe what our body is doing compared to describing static posture. If we start at the foot and work our way up the body, our first action is connecting our heel with the ground. Then we roll over the calcaneus (our heel bone), through the ankle joint, through the forefoot, and then through the toes. We coordinate that with knee extension, hip extension, and spinal extension to propel our body forward.
As we roll through our foot from heel strike to toe-off, our pelvis on that side goes from a slight posterior tilt to a slight anterior tilt. On the other side, our pelvis does the opposite. As we swing our leg through, our pelvis on that side goes from a slight anterior tilt to a slight posterior tilt. Movement of both sides of our pelvis at the sacroiliac joints allows this back-and-forth motion of the pelvis to happen as we walk.
Frontal and transverse plane movement
Along with our movement in the forward-backward sagittal plane, we also move in the frontal plane and rotate in the transverse plane to complete our walking pattern. As we step forward with one foot, meet the ground with our heel, and start to roll into our foot, our pelvis laterally tilts toward our weight-bearing leg, as we shift our weight from one leg to the other. And then as we take another step forward, our pelvis tilts laterally again in the other direction.
To allow and stabilize the action of shifting our weight as we walk, we laterally flex our lumbar spine toward the weight-bearing leg. Our abductors (our lateral gluteals) then have to lengthen a bit in order to let that hip drop. At the same time, our adductors on the other leg engage as we lift the other side of our pelvis. As we step our foot forward, our pelvis also externally rotates and our upper thoracic spine and shoulder girdle counterrotate in the other direction.
What influences our gait cycle?
Since walking is so fundamental to many of our daily tasks, we might think that everyone just naturally learns to walk efficiently. But actually, there are lots of influences that alter our gait cycle. Initially, we learn to walk by modeling the people in our environment. Those people, our parents and other caregivers, almost certainly have their own gait pattern. And that pattern is influenced by genetics, including things like relative bone length, joint angles, flexibility, and other factors. It’s also moderated by activities that we do. What we do with our body creates patterns in it and walking is no exception to that. Repetitive work tasks, habits, and sports/leisure activities can also affect how we walk.
What might disrupt our gait cycle?
Injuries to the lower body will obviously have some effect on how we walk. Because gait itself is so complex, understanding the effects of injuries on walking is all the more complicated. Perhaps less obviously, injuries to the upper body also have the potential to affect how we walk, depending on the amount, duration, and type of compensations that we make to adapt to the injury. Surgical procedures like knee and hip replacements especially affect walking. The stability and function of the replaced joint may not be the same as the other side, creating altered walking patterns.
Walking is one of our most basic functional movements. We walk to complete many of our daily activities. The ability to walk is a foundation for many sports and leisure activities as well. While it is a complex multiplanar movement, understanding the gait cycle can help us better understand so many other types of movement. This fundamental series of movements is the base of much of the other movements we engage in.
Hu, X., N. Zheng, W.-C. Hsu, J. Zhang, H. Li, Y. Chen, K. Dai, and T.-Y. Tsai. 2020. Adverse effects of total hip arthroplasty on the hip abductor and adductor muscle lengths and moment arms during gait. Journal of Orthopaedic Surgery and Research. 15:315-322.