Running - Propelling the body’s center of mass through a trajectory

It sounds so simple, and I guess it really should be. Something we can do at any time and without having to think about it. How did it happen that running has been deconstructed and analyzed to the minutia? For the competitive athletes out there, the break down might make the difference for a win. For the rest of us, it can make the difference in the ease, enjoyment and longevity of our running careers. 

There seems to be nothing more frustrating for a runner than to have some nagging issue that causes them to slow down or even stop. Gosh, they just get so antsy! Go ahead, just try to tell an avid runner to “take a break”. 

Unfortunately, research has illustrated that up to 50% of people who run regularly will experience more than one injury per year. That’s a lot of people! Running injuries are typically due to overuse- movement with abnormal alignment and/or repetitive movements into the same directions. 

I hope to provide you with some interesting information about running and what it might mean for you. Bear with me as there is A LOT of data out there!

Running is primarily a sagittal plane action with some motion side to side, into rotation and in the vertical direction. It has been estimated that 80% of the metabolic cost associated with running can be attributed to body weight support and forward propulsion. The remainder is associated with the leg swing, and maintaining side to side balance. 

The mechanics of running efficiently include several key things. These include the dorsiflexion angle both when the foot lands and when pushing off to begin the flight phase, the knee flexion angle during stance, hip extension angle in late stance, hip adduction angle during stance and the foot/ankle alignment during stance. It’s all about shock absorption and forward propulsion. 

For example, a knee flexion angle of less than 45 degrees is associated with a reduction in shock absorption and excessive loading at the knee cap. Overstriding or reaching your stride out in front of your body with a dorsiflexed foot (toes up position) can reduce shock absorption at the ankle and lead to shin splints. Overstriding can also result in increased and more forceful knee flexion at loading which can lead to patellofemoral knee pain. The lack of hip extension in late stance (especially at faster speeds) can lead to compensatory extension from the lumbar spine or an increase in step frequency which is less efficient.

Higher load on knee and plantar fascia, poor energy storage during loading.

Need more muscle action and stiffness.

Excessive hip adduction. 

Genu valgum, foot pronation. 

Overstride = Heel reaching out in front of the body with toes up and heel strike. 

Increased demand/stress to patellofemoral joint and ankle dorsiflexors at loading. 

Must use more energy to brake.

Graph shows forces acting at the patellofemoral joint at peak knee flexion angles during stance phase.

Note the force at this joint when a person overstrides (black line with *) -It is even higher when there is an overstride with more dorsiflexion at the ankle (highest peak). 

Up to 6 x body weight. 

The running style and foot position of the athlete on the left is recommended for optimal shock absorption and efficiency. Landing with this position allows for better storage of energy which is released during the next push off. 

The runner on the right appears to be overstriding. In addition, his tibia (shin bone) is well behind his ankle and he will most likely end up landing with a lot of force demands acting about the knee.

The phases of running include stance and swing/flight. During stance, we land on the foot to absorb energy acting between the body and the ground. This is also a braking phase in which the motion of the center of mass is slowed. To effectively load and absorb shock we need optimal mobility and alignment across joints as well as the action of the tibialis anterior, posterior tibialis, quadriceps and gluteal muscles. Good joint alignment, mechanics and muscle activation patterns allow not only  for shock absorption but also the ability to store energy for the next launch forward into flight. This push off and launch into flight requires our body to generate power exceeding  the force needed to support our body weight. Much of this power comes from the gastrocnemius and soleus muscles, AKA the calf muscles. The flight phase allows for time to move the other leg forward.  

Graph showing the stance phase broken down into loading/shock absorption/braking followed by propulsion forces at push off

Step frequency is the number of steps taken per minute. Step frequency includes both stance time and step length. For a given step frequency, the longer the stance time, the shorter the step length and vice versa. For increased speeds, a runner can increase the step frequency (reduction in stance time as a result), increase step length or both. Most runners adopt a pattern that lowers energy consumption for their body configuration and this happens at a sub-conscious level.

At faster speeds, the step frequency will increase and again, this forces the runner to generate the propulsive forces needed to leap forward in a shorter period of time. Studies have shown that at sprinting speeds, experienced sprinters have shorter stance times. Flight time increases at faster speeds as well. The flight distance covered during this phase depends on the take off dorsiflexion angle, velocity at take off and the vertical distance of the runner's center of mass between take off and the center of mass at landing. This change in height of the center of mass between landing and take off has to do with the potential and kinetic energy that can be reused between landing and flight. Load then explode! The consensus is that better runners run with relatively short stance times and longer flight times. 

According to the authors of “The biomechanics of running and running styles: a synthesis” from Sports Biomechanics, 2024, there are five distinct running styles. The authors characterized  them by analyzing  step frequency (# steps per minute), stance time (duration of time spent on one foot), step length, flight time, vertical displacement and dorsiflexion (angle created by foot motion towards shin bone or shin bone moving forward over foot) at initial contact. 

The styles are as follows:

Hop: 

High step frequency, shorter step lengths

High vertical displacement with reduced forward propulsion

Low to medium dorsiflexion

Due to reduced hip extension, very upright trunk, reduced leg swing velocity

Bounce:

BETTER PERFORMANCE

Low dorsiflexion

High leg stiffness–muscles are strong and quick- able to reuse elastically stored energy, able to generate higher propulsive forces

Long flight time with shorter stance time

Push:

Short flight time, long stance time with long strides

Medium to large dorsiflexion

Reduced vertical displacement

Stick:

Strategy used at low speeds or when vertical displacement is not desired such as when running in loose sand or with a heavy backpack. 

High dorsiflexion

Long stance time and short flight time

Sit:

Flexed knee at initial contact and loading/stance

Medium step frequency and dorsiflexion

Other authors characterize runners as having a forefoot vs heel strike vs midfoot strike style. Landing on the ball or front portion of the foot places force demands at the achilles tendon and gastroc/soleus (AKA calves)  muscle groups. Landing with a heel strike leads to greater forces acting about the knee and tibialis anterior muscle for shock absorption. This might be why a person who runs off the forefoot might end up with achilles tendonitis. Or, patellofemoral pain and shin splints in a person with a longer stride forward who is landing on the heel. 

WOW! That was a lot of information. When running becomes uncomfortable, don’t hesitate to seek an understanding as to why. Have a professional analyze your posture, your movement, running, strength, and flexibility. This can be incredibly revealing and lead to a training/rehabilitation program which will KEEP YOUR SPECIAL BODY on THE MOVE

Quick tip—Work on ankle dorsiflexion range of motion, hip extension range of motion and, if you are able, plyometric type exercises. 

Because Dr. Jill Trato is a RiseUp member, she offers a free 30-minute evaluation to anyone from our community. Just mention RiseUp and she’ll take a look, give you personalized advice, and help you understand what might be causing your pain.

If you’ve been struggling with anything from nagging knee pain to more persistent issues, this is a perfect chance to get expert guidance at no cost. Contact Jill here

About Dr. Jill Trato, PT, DPT, NCS: Dr. Jill has been in practice for over 21 years specializing in the differential diagnosis and treatment of balance, neurological, movement and vestibular disorders. In addition, Dr. Jill has completed residency training in Proprioceptive Neurologic Facilitation, extensive training in manual therapy for orthopedic conditions as well as fellowship coursework in the movement sciences applicable to the orthopedic and chronic pain populations.Dr. Jill's approach is whole person focused and efficient. And, she thoroughly enjoys just getting to know you as an individual.