Running Mechanics: The Introduction

 Photo Credit:  New Basin Blues

Photo Credit: New Basin Blues

With 36 million people running in the United states, running has become a big area of study. When it comes to running gait (running much like walking) it will vary from runner to runner according to specific muscle imbalances. For this reason, it is difficult to standardize the “Perfect Form”  however there is research to support what “normal” running should closely resemble.  Why is this important? It is important because within the running community there is an incident of injuries as high at 79%, most occurring at the knee. Therefore, you have to think along the lines that these athlete run hundreds of miles a year, there is a repetitive stress, and the ones that are injured may be moving sub-optimally.  The purpose of this post is to introduce basic running mechanics so that we can further analyze gait in the next post. 

 

Running is sport that requires repetitive impact and push off . Each time the foot hits the ground the foot, knee, and hip have to withstand and tolerate a ground reaction force 2-3 of our body weight (5).  The demand is VERY HIGH, therefore before I even get started I want to make this statement as clear as possible : YOU HAVE TO BE FIT TO RUN, at least run with less probable cause of injury. 

 

There are major 2 phases of running, and they are the stance phase which makes up about 30% of gait, and the swing phase which makes up 70% of gait. The faster we run, the shorter the stance phase becomes (3).

 

The stance phase is the period in which the foot makes contact with the running surface and this phase is made up of 3 components: foot strike, mid support and toe off. 

Stance Phase: 

A: Foot strike

This marks the beginning of the stance phase, it occurs when the foot first makes contact with the ground.  Lets imagine that both feet are floating off the ground and you are about to land with one leg, that initial second you touch the ground is foot strike. 

There are 3 ways runners strike the ground, and that is with either their heel  (heel-strike) the middle of the foot (mid-foot strike) or with the balls of the feet (Forefoot strike) (2). About 75% of runners land with their heel, 25% with the midfoot and forefoot (5). 

The major differences between the two striking patterns is that heel strikers land in more dorsiflexion (ankle flexion) and research demonstrates that ground reaction forces are more evenly distributed into the ankle and knee. Is has been shown in some studies that heel strikers tend to absorb shock better than forefoot strikers- mostly because there is an increase in hip and knee flexion which acts as a spring.  Their counterparts land in plantarflexion (ankle pointing/extension) and most energy absorption at foot contact is absorbed at the ankle. 

 

What should we see at foot strike? 

In this phase the fundamental goal is optimal energy absorption throughout the lower quarter.

Angles to look for at foot strike are centered at the hip and knee.

Hip: >25 degrees of hip flexion

Knee: 30-40 Degree Knee flexion

 Photo: From Powers et al- Movement Performance Institute

Photo: From Powers et al- Movement Performance Institute

 

The stiffer a runner lands in will lead to an increase in unnecessary stress at the hip and knee joints. 

The  peak Muscle activity seen during this phase are as follows: 

·     Posterior tibialis: because this muscle will help control pronation of the midfoot as it loads

·     Peroneals: controls midfoot especially with those than land with the midfoot

·     Glutes: as they are suppose to stabilize the hip/knee. 

·     Quads as they assist in eccentric load during knee flexion 

jessgaitt.JPG

B: Mid Support

The start of the mid support phase of stance begins when the whole foot makes FULL contact with the ground and end right when it begins to roll over the toes. 

This is a critical part of the stance phase because this is where the body will need maximal pelvic, knee, and ankle stability. 

 

What should we see at mid support? 

This is where we will see the biggest deviations! This is the frame we should all pay attention do when doing running gait analysis. 

Optimal joint angles:

Hip Flexion: >25 degrees

 Powers et al: Movement Performance Institute (L picture faulty; R- optimal )

Powers et al: Movement Performance Institute (L picture faulty; R- optimal )

Knee Flexion: 40 degrees

Forward Trunk lean: 10 degrees

Lateral trunk lean: <5 degrees

Knee valgus of Varus <5 degrees

Pelvic Drop < 5 degrees

Minimal anterior pelvic tilt

Limited foot pronation

Knee in line with toe

Foot not crossing midline

The Peak muscle activity seen during this phase are as follows: 

·     Gastroc, peroneals, posterior tibialis: as they control the drop of the forefoot onto the ground

·     Glutes: as they are to stabilize the hip, during this phase we see many faults such as the hip drop if the glutes are not strong enough to support and stabilize the pelvis. 

·     Quadriceps: as they eccentrically support the knee and allow for proper shock attenuation through knee flexion

Faults seen: 

-       Excessive midfoot pronation

-       Excessive Hip drop

-       Knee diving in (valgus) or out too much (Varum) 

-       Trunk too erect

-       Trunk leans too much to one side

-       Foot crossing midline 

-       Knee past the foot 

Injuries from these faults just lead to increase shock which can lead to injuries such as knee, hip, low bac, ankle pain- Achilles tendonitis, plantar fasciitis, patellar tendonitis, stress fractures. 

 

C: Toe Off

During toe off phase the heel lifts off the ground and the toes begin to leave the ground. Here the glutes and calves should provide little power for push off. It is what I call the “going along for the ride” phase.

Here we should see about 10 degrees of hip extension.

In the runners with stiff hip flexors we may see faults as excessive low back extension, or rotations of the pelvis. 

As the toes leaave the ground we move into the swing phase. 

SWING PHASE

jessgait.JPG

The swing phase begins once the toes leave the ground and ends when the foot is about to strike the ground again. 

The swing phase in made up of 3 smaller components: the follow through, the forward swing, and foot descent.

 

D: FOLLOW THROUGH

During the follow through phase of swing, the foot leaves the ground up until right before the knee begins to move forward. 

The peak muscle activity is seen in the:

·     Quadriceps: as they help control how much the knee bends 

·     Hamstrings as they help bend the knee

·     Hip flexors: as they help control and limit hip extension and assist with flexing the hip to allow the leg to come forward.

Faults:  Hip drop, inner thigh (femoral) coming towards the center 

 

E. Forward Swing

In the forward swing phase the leg moves forward and knee begins to straighten out and reach out in front, and transitions into the foot descent phase.

During this phase the hip and knee bend forward which help propel the body forward. 

The peak muscle activity seen in the following: 

·     Anterior Tibialis: as they help clear the foot from the ground

·     Hip flexors: help flex the hip up 

·     Hamstrings: as they help control hip flexion eccentrically

F: Foot Descent

 During this last phase of swing, both legs are gloating off the ground and the foot is traveling back down towards the ground. You will begin to see knee extension as the leg reaches down. 

The peak muscle activity is seen in the: 

·     Anterior tibialis: as it helps eccentrically control plantar flexion (toes pointing down_

·     Quadriceps: as they help extend (straighten) the knee

·     Hamstrings: as they assist and help control knee extension, as well and begin to extend the hip as the leg drops down towards the ground. 

 

We can’t exclude the upper body when talking about running gait because it does play a big role. The arms swing in order to counter balance the leg movement and help balance the trunk as well (3) It must be said that in order for the hips and legs to move through the cycles, it does require a relatively strong and stable trunk . A strong and stable core helps absorb impact forces. Remember that our pelvis and legs attach to the trunk, so if your base is not stable, then you cant expect your lower quarter to work as efficient. 

 

 

 

References

1. Byl, N., Davis. I., Heiderscheit B., Powers. C. 2013 Research Symposium- The Science of Running,2013. CPTA Nov 9-10. 

2. Davis, I., Rice. H.M., Wearing S.C. Why Forefoot Striking In Minimal Shoes Might positively Change the Couse of Running Injuries.  Journal of Sports and Health Science. 2017. 1/9

3. Nicola, T. Jewison D. The Anatomy and Biomechanics of Running.  Clinics in Sports Medicine31 (2). 187-201 , April 2012. https://www.researchgate.net/publication/221838595_The_Anatomy_and_Biomechanics_of_Running

4. Novacheck T.F. Biomechanics of Running. Gait and Posture. 1998 77-95

5. Powers, C. The Influence of Abnormal Hip Mechanics on Knee Injury: A Biomechanical Perspective. Journal of Orthopaedic and Sports Physical Therapy. 2010. 40:2  http://movementpi.com/wp-content/themes/movement_pi/publications/Hip_mechanics_and_knee_pain.pdf

6. Souza R, Powers C. Differences in Hip Kinematics, Muscle Strength, and Muscle Activation Between Subjects with and without Patellofemoral Pain. Journal of Orthopaedic and Sports Physical Therapy. 2009 39:1 http://movementpi.com/wp-content/themes/movement_pi/publications/Hip_strength_and_motion_in_patellofemoral_pain.pdf