Healthy Movement for Life - Running
By Dr. Jill Trato, PT
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 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.
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.
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.