Any person would say “when I run, I move my legs and arms and that’s it”. Well, I am really sorry, but I have to inform you that any movement of the body is very complex and so is running. Of course, we all are different and our running will differ from one person to another, but there are common biomechanical similarities: joint movements and muscle firing among others.
In this post I am going to explain to you the running phases, how your body works when running. This is called “running gait cycle” and it is defined as the series of movements of the lower extremities (legs) which begins when your foot makes contact with the ground, and ends when that same foot makes contact with the ground again. Note that your arm movements also play an important role in running, although it is something I will talk about in the future.
The running gait cycle is divided into two main phases: stance phase (the one I will talk about in this blog post) and swing phase. In brief, stance phase is when your foot is in contact with the ground, while swing phase is when your foot is in the air.
Let’s start with the stance phase and later on I will dedicate time to the swing phase.
The stance phase is considered as the most important of the two, as it is when your foot bears (support) the body weight. The stance phase is divided into three stages. It begins with foot strike, followed by midstance and then propulsion. Different muscle groups, bones, and joints are acting uniquely in each of these stages.
1. Foot strike or initial contact
Foot strike or initial contact is the moment (whether you land on your heel, midfoot or forefoot) when your foot touches the ground after having been in the air. At the beginning of initial contact, the muscles, tendons, bones, and joints of the leg act to absorb the impact of the landing. The landing is facilitated by pronation (rolling in) of the foot caused by the subtalar joint (joint between the heel bone and astragalus) and plantar fascia stretch that allow the foot to expand. Both, pronation and plantar fascia stretch, act as impact absorbers.
Also, dorsiflexion occurs at the ankle, accompanied by knee flexion (bending), and hip motion, to distribute the force of impact. Rectus femoris (one of your quad muscles) and gastrocnemius (one of your calf muscles) transfer the force of impact from your ankle to your knee and then to your hip.
The foot will absorb up to 3 times your body weight when striking the ground. This is the reason why it is so common to get injuries when you are a runner.
2. Midstance (you may also hear it referred to as single support phase).
Midstance is the stage where you transfer weight from the back, to the front of your foot. The leg is directly under the hip, taking maximum load (maximum risk of injury) as the body weight passes over it. The other foot is in the air, so all the body weight is borne by one leg. The ankle and knee are at maximum flexion (bending).
In this stage the foot begins to move from pronation to supination. This pulling motion is enhanced by the contraction and push-off motion caused by the gastrocnemius, soleus (both calf muscles) and Achilles tendon, which cause ankle plantar flexion and allow the following stage to begin.
Note that if in this stage pronation has not stopped, it might be due to ankle instability (too much movement/poor control). As I told you previously in this blog, pronation is necessary and many therapists and trainer retailers try to stop it from happening which could be a big mistake. It might mean higher stress for your joins and muscles.
Propulsion begins when your heel lifts off the ground to allow your toes propel you forwards. To get this, your ankle, knee and hip have to extend (straighten) and your leg will use the elastic energy stored at previous stages. The more elastic energy stored the less your body has to use the muscles (economy of the exercise).
Once the big toe of your foot leaves the ground, this phase will be over. Now, both of your feet are in the air and this is one of the differences between walking and running (when you walk, one of your feet is always touching the ground).
As the big toe turns upwards (dorsiflexes) the windlass mechanism comes into play, tightening the plantar fascia and helping to raise the arch of the foot. I explained this mechanism in a previous post that you can see here.
During propulsion the foot should be supinated (rotated outwards).
Find below a video with your foot movement in the stance phase.
I do understand that this is a very simple way to explain the running gait cycle. The reason is that this is an easy way to understand the basics for those that are not much into running and anatomy yet. Check out this link about the biomechanics of running if you want to find more in-depth information.
Comments are welcome, they are always helpful for everyone.
If you have any questions, do not hesitate to contact me on The Physical Therapy, Physiotherapy Clinic based in Southampton, and I will be happy to help you.