Biomechanics of running


Running, it seems easy all you have to do is just put one foot in front of the other and swing your arms back and forth and that is right? Unfortunately it’s not that simple, 90% of all runners get injured at some point in a year. The nature of running produces a very repetitive movement and most injuries are due to over use or overstraining. So being the most efficient when running will help to reduce the chance of getting niggles. Furthermore we have shoe manufacturers to thank for the rapid increase of research into biomechanics as they all compete to make the best shoes possible. You only have to go into a running shop and look at the wide variety of shoes on offer from neutral shoes to barefoot and trail shoes, gone are the times of the simple white trainers.

Initial contact > early stance > mid stance > late stance > pre swing or swing generation > Swing absorption + stance absorption > Initial contact

When you run both of your feet will be airborne twice in each cycle.

anatomy of leg

Initial contact: One foot touches the ground.

Foot:Back of the foot starts to till outwards.

Tibialis Anterior (the muscle along the front of your shin): control the contact of the foot with the ground

Hip extensors:are working their hardest just before and after initial contact to create the momentum for your gait.


Early Stance phase

Hip: Moves thigh inwards controlled by glut medius. Glutus medius generates and controls and limits of the hip to keep it relatively stable for all of the stance phase. The more your hip is stable less movement you will have through your shoulder and head are going to be used to try and generate force.

Plantar flexors (gastronemius + Soleus)support the trunk till pre swing phase due to hip interactions which accelerate the trunk upwards.

Quads: Will work to lengthen and contracts in order to bend the knee. This will help to tilt your hip slightly forward and bring you knee up, to begin your stride reducing the forces that are going through your leg. It will also work to absorb the shock from the leg from the initial contact with the ground through the tendon and the muscle itself. The rectus femoris (part of the quadriceps) is only involved in the early stance and not the other stance phases.

Hip extensors:continue to generate power as the hip rapidly extends

Tibialis Anterior: controls the lowering of the forefoot


Mid Stance

The pelvis drops until start of double float (when both feet are off the ground).

Gastro + soleus: Works to increase and control the hip tilt and the forces going through the pelvis throughout the rest of the stance phase. They try to do this with minimal effort, this is helped by keeping your pelvis stable. 45% of the power from soleus itself the rest of the calf both the other muscles at the front and the gastro will contribute to the rest.

Tibialis Anterior: moves your foot up to the sky in order to provide clearance for your ankle in swing

Hip flexors: Are most dominant in this phase as they work to reduce the rotation of the upper leg to bring the knee up as straight and high as possible for the swing. The main muscle involved is called psoas.

Achilles tendon: The energy produced by the gastos + soleus will build up and get stored in the Achilles tendon.


Late stance

Quads: The most active quadriceps in this phase is called Rectus Femoris and it works to produce the force to bring back both the knee + hip. It will also have some help from your gastro surprisingly as well as do the opposite motion to your soleus.

Soleus: This muscle will work to tilt and maintain the position of the hip rather than help to increase the forward tilt of your pelvis. Your soleus will be working harder than your gastros in this phase.

Gastros: Will work to generate power to help move your leg forward rather than relying on the momentum that has built up from your core and your hip muscles.


Pre-swing (swing generation)

Soleus: Is still working to help redistribute the energy around your core and trunk in this stage by bringing your knee down ready for the contact with the floor. Gastros will also work with it to point your toes

Hip flexors: start to work at their maximum.

Achilles tendon: This is when the Achilles tendons tarts to work as a spring and will release the power and forces that the calf has produced so far.

Post tibialis, Achilles, heel + foot: control movement of your ankle to point it towards the sky

Quads: have very little involvement but rectus femoris will work to prevent your knee from going into too much flexion.

Hip flexors: continue to really work hard during this phase.


Swing absorption + stance absorption

Knee: At the start of the swing phase your knee will be flexed to 45 degrees (to create the high knee effect) it will then be reduced to around 25 degrees. The quicker your knee can be brought down from its highest point the faster you will go.

Ankle: Will be pointing up to the sky as it moves to clear the ground and transfer to the other foot

Foot: Will start to move in and roll onto the arch, which will allow it to work as a shock absorber.

Quads: Especially rectus femoris start to contract to prepare for the contact of your leg with the ground as well as to help absorb the impact.

Hamstring + hip extensors:will continue to extend hip until 1st half of stance.

Hamstring: decelerate momentum of lower leg and work to controls the movement of the knee as it bends back to prepare to make contact with ground. Your hamstring will also work to prevent too much extension at the knee.

Hip extensors: Are working at their maximum amount generate force just before toe off


Back to initial contact



muscle activiation gait
When which muscle is activated in the gait cycle Mann & Hagy (1980)

When which muscles are working at their max:

Hamstring, gastros, soles and glutus maximus: late stance phase to the beginning of swing phase and then uses the momentum and force transference to carry you through the cycle.

Hip extensor: Second part swing + early stance

Hip flexors: Toe off

Arms: There is some debate on to the effect and use of your arms especially in generally running not sprinting the theory is that it helps maintain momentum of lower extremity. So you run more efficiently as well as help to increase momentum.

Pelvic movement: The amount of movement in the pelvis is the same no matter the speed you are doing. However as the speed the forwards tilt of the pelvis will increase as it try’s to generate more power and force to move forward and increase the stride pattern. As you get faster and have built up some moment your centre of gravity will move further back as you don’t need to keep to keep generating the power its more about maintaining it.

Tendons: Will act as spring to work to absorb power generated from the muscle contracting. The tendon will then be stretched and after will effectively recoil to release the force rather than it being spread throughout the muscle belly of the calf.

The transferal of energy: This occurs throughout the gait cycle and when your leg will mostly be placed on your rectus femoris in your quads and your bicep femoris in your hamstrings as they have two attachment points. Therefore they are able to cross the joints of the hip and knee to dissipate the forces through the leg much better than the other muscles.


Effect of increasing speed

Foot mechanics: contact goes from hind foot to the fore foot, the amount of hip and knee flexion will increase which in turn will increase your stride.

Road runners: 80% will and on the heel of the foot with the other 20% landing on the mid foot

Sprinters: Almost always will only land on the ball of the foot.

Effect of Terrain: Different terrains will have different effects on your biomechanics as you will be placing you feet differently in each scenario. For more for information on the effects on your biomechanics while using a treadmill check out my other blog post.


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Novacheck TF. Walking, running, and sprinting: a three-dimensional analysis of kinematics and kinetics. AAOS Instructional Course Lectures 1995;44:497–506.

Novacheck TF. (1997) The biomechanics of running and sprinting. In:Guten GN, editor. Running Injuries. Philadelphia, PA: W.B. Saunders 2:4–19.

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