Believe it or not we have been running just as long as we have been walking, it is as if it is pre-programmed into our DNA. Running comes naturally to us and many people choose running as a convenient and safe way to exercise during lockdown, but not surprisingly the number of people injured while running has also increased. The percentage of runners who experience running-related (re)injuries can be as high as 80%.
There is a correlation between increased risk of injury or re-injury and biomechanical inconsistencies while running, along our kinetic chain. Therefore, an understanding of the biomechanical circumstances that cause soft tissue and joints to fail during sprinting and running is required to improve rehabilitation specificity and performance. Biomechanics of running is basically the study of how our body moves (kinematics) and the relationship between those movements and the forces that causes them (kinetics). The following forces act on the body while running; impact force, drag force, gravitational force/pull and friction force.
If we want a deeper understanding of our running form, we need to have a basic understanding of the gait cycle. Gait analysis and assessment is complicated since there are so many moving parts and every runner has their own unique predetermined style. So, how do you get from one foot to another while running? 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 phase and the swing phase. 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.
The stance phase is marked by the foot’s initial contact with the ground (foot strike/ loading response), midstance through toe-off (single support phase) and take-off (terminal stance). This phase has been measured at approximately 40 percent of the gait cycle; however, for elite distance runners and sprinters this is considerably less. The quadriceps group, specifically the rectus femoris, is heavily active before initial contact. Once contact is made, the muscles, tendons, ligaments, bones, and joints of the foot and lower leg function to dissipate the impact of the landing. Gluteus maximus, minimus and medius are active at the beginning of stance phase, and at the end of swing phase.
Normally the outside of the back of the heel is the first point of contact. As the foot hits the ground and lowers, the heel will roll down due to motion at the joint below the ankle, the sub-talar joint. Pronation of the foot is somewhat slowed by the tibialis posterior tendon at this point. A few degrees of pronation is normal as this helps to absorb the reaction shock of landing by spreading the force throughout the mid-foot and causes the rest of the foot to become mobile and therefore able to adapt to varying surfaces and angles.
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 tendon, posterior calf strain, lateral knee pain, and iliotibial band tightness. Conversely, an overpronated foot at midstance can result in tibia pain, anterior calf injuries, and medial-side knee pain because of the internal rotation of the tibia.
As the inside forefoot lands, the tibialis anterior tendon towards the front of the ankle controls the motion. The body’s centre of gravity passes over the foot and the heel begins to rise, then turn inwards again, with a motion called supination. This causes the foot to become rigid so that it is a good lever for pushing off. This motion is assisted by contraction of the peroneus longus muscle, as it stabilises the big toe against the ground at 50-60°, and tensions the plantar fascia, increasing stability. The calf muscle contracts rapidly, helping lift the heel and push the lower leg into the swing phase of the step.
The muscles and tendons store elastic energy during the stance phase which recoil in the swing phase to re-accelerate the body. 50% of which comes from the achilles tendon and this cyclical behaviour permits efficient force production and avoids high costing mechanical energy loss.
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. After the initial contact and midstance positioning, the hamstrings, quadriceps, hip flexors, 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 because 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.
Upper Body + Core
So far, we have only talked about the lower body, but the lower and upper body are linked together as one unit and plays a large role. First, you should run with an upright body posture with a very slight lean forward from the ground, not from the waist. The arms and legs should work in a coordinated fashion.
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 move 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 of upmost importance. An unstable core could potentially lead to injury because of the gait cycle being negatively impacted. As we run, we absorb 6-8 times our bodyweight with each foot strike (Newtons 3rd law of motion), if we put repetitive force in abstract positions due to instability, lack of coordination or body control we can run into overuse injuries such as stress fractures and runner’s knee.
The integration of the arms and legs is crucial. A lot of time we see something happening with the leg that is incorrect and immediately work on fixing the problem by adjusting how that leg is working. For example, if an athlete overextends the lower leg, we immediately try and correct them by having them put their foot down sooner. Instead, the problem seen with the leg could simply be the symptom. The real cause could be in the arm swing. The arms function to stabilize and balance, each arm counterbalances the opposite leg, so when the right leg swings forward, the left arms swings, and vice versa. Also, the arms counterbalance each other, keeping the torso stable and in good position and ensuring that arm carriage is forward and back, not side to side in a swaying motion. Poor arm carriage ultimately costs the runner both by hindering running efficiency as stride length is shortened and running economy deteriorates as poor form requires a dramatic increase in energy consumption. All this allows you to efficiently transfer the energy from your aggressive arm strides, through your torso, and into your legs – all of which leads to a greater power output.
Implementing proper breathing mechanics during sprinting and running can have a huge impact on your performance. When you breathe deep into your lungs, you start to use your deep inspiratory muscles to draw air in and out of your lungs. This deep inspiration causes your thorax and ribcage to expand. This places your thoracic spine in a much more advantageous position, where is better able to rotate freely every single step. The thoracic spine needs to be able to move completely uninhibited to allow correct rib function.
The relationship between the pelvis, ribcage and skull is quite interesting as when the pelvis rotates right, the ribcage rotates left and the skull to the right. This means a deviation in range of movement in any area will result in compensatory patterns and therefore dysfunctional running mechanics.
Stride Length and Frequency
The rate of change in the running disciplines has the same repeating dynamics: acceleration, reaching maximum speed, maintenance, and deceleration. Depending on the race distance, these areas are different and are affected by the experience of the athlete and their running technique. Speed = Stride length X Stride frequency, it’s that simple. Change one of these variables to suit your needs and running mechanics and you will run faster, more efficiently and decrease the risk of injury.
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