What are normal biomechanics?

  

Normal biomechanics and the gait cycle


The mechanics of walking or running is broken down into 2 main phases 


Stance phase:- The period of time where the foot is in contact with the ground (around 60% of the gait cycle)

Swing phase:- The period of time where the foot is in mid air swing through to take the next step (around 40% of the gait cycle) 



The 2 phases of gait can be broke down further into key characteristics that should be seen in "normal" walking. There are numerous different walking patterns but there are fundamental points each phase of gait that should be seen. When these are absent then these altered biomechanics can be the reason for symptoms to develop. Some further details around conditions caused by abnormal gait can be seen in our conditions page.Please click here for further details of conditions related to altered or abnormal biomechanics 


Further details of the key characteristsics of stance and swing phases of gait are given below

Stance phase


Consists of 60% of the gait cycle and is broken down into the following into 2 further sub-phases. These relate to the need for the foot to cushion the leg (shock absorption phase) and the 2nd sub-phase where the leg is preparing to propel the body onto the next step (propulsive phase)


1. Heel strike (Beginning of Shock absorption sub-phase)


This the period where initial contact of the foot on the ground takes place. As the heel strikes the ground, the ankle position is usually around 90 deg to the leg. Rotation at the ankle takes place as the under side of the foot moves towards the ground. (plantarflexion)


As the foot moves towards the floor (plantar flexion of the ankle) the knee and hip prepare to accept the weight of the body. The knee may begin to bend (flexion) slightly, and the hip muscles stabilise the hip joint.


2. Foot flat


Foot flat describes the point where all of the foot should now be in contact with the ground. The knee bends to anywhere between 15-25 degrees which cushions the leg against the shock of impact. This protects the joints from loading directly, and instead the leg muscles help deccelarate the leg.


Ankle:- The leg initially lies backwards (reclined) and the shin bone (tibia) then rotates around the ankle joint as the shin bone moves toward 90 degrees. This progresses the body forward


Foot:- The foot also begins to roll inwards slightly (pronation) again to absorb the shock of impact and weight on the leg.


3. Mid stance (end of shock absorption sub-phase)


At mid-stance the full weight of the body is now through the leg. The leg is now vertical and the hip muscles have controlled the upper leg and back to be upright for all of the weight to be directly above the weight. Immediately after this point the weight lne negins to shift in front of the foot.


Ankle:- The ankle joint has now moved from a reclined (plantarflexed) position to a vertical position (ankle angle 90 deg) and then beyond into an inclined (dorsiflexed) position


Foot:- The foot has now rolled over to it's maximum position of pronation



4. Heel off (Beginning of propulsive sub-phase)


After mid-stance the weight of the body is now in front of the leg and the hip muscles now have to work again to keep the body upright. The leg is now preparing to propel the body forward and accelerate, with the calf muscles (plantarflexors) beginning to engage.


Ankle:- The shin bone is now inclined forward (dorsiflexed) to about 10-15 deg, and after this point  the calf muscles (Gastrocnemius, Soleus and Posterior tibal muscles) begin to work. At this point the ankle moves downwards (plantarflexes) to propel the leg forwards and upwards.


Foot:- The foot is now no longer acting as a shock absorber and works with the ankle as the muscles described above start to act on the foot to become a lever to accelerate the leg. Ordinarily the foot will roll outwards (supinate) to place the foot in a position of mechanical advantage.

The toes also flex, in particular the 1st toe which also helps to improve stability of the foot.




Swing phase


The period of time in walking where the foot is off of the ground is classed as swing phase. The foot leaves the ground and "swings" through, past the weightbearing leg and then prepares to make contact with the ground again into stance phase again (described above).


Swing phase is broken down into 3 main phases


1. Early swing (immediately after the foot leaves the ground)


As the foot leaves the ground it starts in a plantarflexed position (pointing downwards). The hip is in full extension, and the knee is slightly flexed initially. The hip flexors then pull the leg forward to assist, and at the same time the dorsiflexors begin to pull the foot up slightly.



2.Mid swing (the leg comes level with the weight bearing leg)


The leg has now began to gain momentum and is swing forward in a pendulum like fashion accelerating forward. The hip is now in a more neutral position, the knee still slightly bent and the ankle is now again at 90 degrees to ensure the leg clears the ground when swinging through.


3. Late swing (Leg prepares for weight bearing again)


The leg has now swung past the weightbearing leg, and begins to decelerate as it prepares to take weight again in stance phase. The knee becomes fully extended and the foot is at 90 degrees to prepare for heel strike and the beginning of stance phase again





What do I need to do to book an assessment?


We offer a free no obligation biomechanical assessment in our Orthotic and biomechanics clinic in Hamilton (near Glasgow). During this assessment we will give you a detailed assessment of the mechanics of your body.

Sport Orthotics are based within the Treatment Hub clinic in Hamilton near Glasgow and have a wealth of experience in biomechanical assessment, orthotics, sports injuries and Podiatry.

We also have a team of people we work with from Orthopaedic Surgeons, Podiatrists, Sports Therapists, Yoga and Pilates instructors. So if we can't help you we defintiely know someone who can!


How do I book my free no obligation biomechanical assessment?


Our clinics in The Treatment Hub in Hamilton, South Lanarkshire (near Glasgow) operate an online booking system for all 3 of our bioemchanics specialists. To book your free bioemchanical assessment click on the link below and select the clinician diary you wish to access