Simple View of Running Biomechanics

Jason Price, MS, CSCS, ATC, LAT, CPT, USAW Club Coach

Running technique is about timing and coordination.  If you have proper timing they you are coordinating your movement and muscle contraction to create what appears to be an effortless flow of motion.  But, if your technique is flawed then it is apparent the effort it takes to coordinate the running movement.  Most research on running injuries points to improper technique as the main reason for injury. 

There are major differences between sprint form and long distance running form but for the sake of keeping this article simple we will look at the basic differences in the types of running.  The reason for the differences between the two types of running is mainly because of the force required to sprint at full speed and the range of motion required by the joints to reach sprint speed.  In both types of running the posture of the torso will be erect with the head held in a neutral position.  The arms should be relaxed and in a 90 degree position at the elbow.  Sprinting will require the thigh to be brought to a near parallel to the ground position with the foot striking under or near the hip.  The foot will strike the ground from either a ball of the foot to heel or with the whole foot at one time.  In longer distance running the thigh will not raise up as far and the touchdown of the foot will be slightly in front of the body creating a longer support phase.  In sprints the distance between thighs in the flight phase will be much greater than that in long distance running, approximately 145 to 160 degrees in sprinting to 90 in long distance running (1).

Running technique can be broken down into three phases:  Pushoff phase, flight phase, and support phase.

Pushoff:

The pushoff phase of running technique involves mainly just full ankle extension to propel the hips forward.  This propulsion of the hips forward must be met with keeping the torso erect and slight hyperextension of the lumbar spine may be noted.  The more forceful the ankle extension the greater the force pushing the hips forward will be.  During the pushoff phase the knee will not fully extend.  Dr. Yessis in his book “Explosive Running” describes the knee action during pushoff this way: “All too often, athletes and coaches recommend full leg extension in the pushoff, believing this is the main force-producing action.  But, straightening the leg fully gives you more of a vertical, rather than a horizontal, force component.”  This statement by Dr. Yessis runs contrary to what many people think.  But, during pushoff the hip extensor muscles are not contracting to push you forward.  They are actually relaxing so that your pelvis is maintained as a fused unit with the push off leg.  So the knee must not be allowed to fully extend until pushoff is completed. 

On the other side of the body the swing leg is being driven forward during the pushoff phase.  This is initially done by the powerful hip flexor group of Rectus femoris, Illiacus, and Psoas major and minor.  But this is only while the thigh is behind the hip following that legs pushoff phase.  After the initial movement forward of the thigh it is moving on momentum created by the hip flexor muscle group.  During sprinting this hip drive will be very forceful and the thigh will carry to about a 75 to 90 degree angle to the hip.  When the thigh is driven forward the shin will “fold up” (1) under the knee to allow for momentum to carry the thigh forward.  As the leg prepares for touchdown and the flight phase the shin will swing out to lengthen the leg.  This straightened leg is used to created force when it is then pulled back towards the ground later in the running cycle. 

The arm action during push off will be opposite of what the legs are doing.  The arms should maintain a mostly forward and back path with minimal side to side movement.  Utilizing the arms inappropriately or not enough can lead to plenty issues themselves. 

Transition to the flight phase occurs when the toes of the pushoff leg leave the ground.  At this time the leg will continue backwards briefly before the knee bends and the leg is then prepared to become the swing leg and be driven forward.  A key point in regards to injuries is that during this phase of the running stride often the heel will strike the buttock.  This is not proper form and the increased activity of the hamstring muscle group during such a flaw may lead to a hamstring pulls.

Flight Phase:

The flight phase lasts about as long as the stance phase.  During the flight phase is when your thighs are going to be furthest apart.  During sprinting this will be about 140 to 160 degrees apart and in long distance running between 90 and 110 degrees (1).  As the swing leg is driven forward it is slowed and eventually stopped by contraction of the hamstring muscle group.  As this is occurring the Shin of the swing leg will unfold from under the knee and the leg will be extended to create long lever geared toward creating force.  On a injury side, this is going to be one of the areas that most people will run into problems when returning from hamstring injuries because it is where the hamstring will be most vulnerable.  By the time the pain of injury is experienced the leg is in contact with the ground so it is often miss interpreted as the ground strike as to what is injuring the hamstring but it is the elongation of the hamstring after the shin swings forward and the hip is flexed that is where the injury occurs or re-injury. 

A key term here is the Paw back.  This is where the elongated leg is then forcefully driven back towards the ground.  This paw back motion is performed until the foot strikes the ground.  In full sprinting the force of ground contact can be many times greater than body weight and are blamed for many injuries.  But, one forgotten point is where the foot is striking the ground.  If it is striking way in front of the center of gravity of the body then it will act as a break and will slow the individual down until they are back into the pushoff phase.  So the foot contact should be as close to the center of gravity of the body as possible to maintain forward momentum. 

Support Phase:

This phase is the transition between the flight phase and pushoff phase.  During this phase the body is maintained in an erect posture while the legs transition their roles.  It is a brief moment where some of the muscles will relax and prepare for contraction again.  From the side a runner should look like they are running level to the ground only with slight variances up and down.  This slight up and down motion is greater in long distance runners than in sprinters.   But, that should almost not be noticeable in live motion.  But, if there is a noticeable sinking of the body during the support phase this may be indicative to having some weakness in the stabilizing muscles of the hips and pelvis.  This sinking action will make your running very inefficient and should be corrected as this will then place more stress on the legs to generate more force and this may create injuries that are totally preventable.

During this support phase the ground reaction forces are stored by the muscles of the legs for return through pushoff.  Our muscles are designed for this force storing feature and it is this function of muscle and connective tissue in muscle that allows for us to be such powerful runners.  This function of returning energy through the push off is why we need to focus on eliminating running with the heel strike when the swing leg comes back in contact with the ground.  Unless it is the ball of the foot or mid foot that strikes first then the energy of the ground will travel up the leg and will not be utilized and the energy will be lost.  This is what often causes many injury issues in many runners’ legs.

To conclude this brief explanation of running technique lets evaluate one of the Statements Dr. Yessis makes in his book “Explosive Running”. He states that no matter the skill level of the athlete or runner technique can be improved.  One of the best ways to make athletes faster is to examine their running technique via filming and take a closer look at exactly what they are doing with their body.  By cleaning up their running form and implementing simple form improvement drills and flexibility and mobility drills the individuals can see huge improvements in speed and endurance. 

References:

1.       Yessis, Michael. Explosive Running: Using the Science of Kinesiology to Improve Your Performance.  McGraw Hill. 2006.

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