CH 15: Introduction to Gait and Footwear

If you are not everting enough on foot

Blue line -Does not make it over the ball of the foot. You are not able to absorb much force from the ground, you can develop injuries associated with overuse due to the repeated force application on the foot.

Two things to change how fast you run

Change your stride length -up to a point Change your stride rate -after stride length max is depended on the rate. (how fast you are taking your steps)

Cushion shoes and motion control shoes (shoes that help with ankle)

Cushion(right) -Individuals with a stiff arch and foot is not everting enough -Typically thicker midsole -exaggerates what eversion is there Example: HOKA shoes motion control (left) -reduce/slow eversion -Perfect for individuals with flexible arch, excessive amount of eversion during stance, wearing the medial aspect of the shoe, -Typically has a darker/grey area on the bottom of the shoe has a density -to reduce eversioon Buy shoe based on comfort, not color.

The "dual peak" of a rearfoot-strike ground reaction force plot

First peak - loading response -When your foot hits the ground and you are getting a push as the foot contacts the ground. Second peak - propulsive peak -pushing off the ground -pushing yourself forward -It will always be much larger than loading response Forfoot/heel striker -Just one peak

Subtalar Joint Kinematics (Frontal Plane) - Percent of Gait cycle

From 0-30% (From loading response till the end of midstance you start with the position of inversion, but the action is eversion. -Eversion is part of pronation (dorsiflexing). -This unlocks the ankle bone and makes it a good shock absorber. From 30-60% -The action changes positions from eversion to inversion. (terminal stance** to preswing). Inversion is a part of supination (plantar flexion). This locks the ankle bones together. It makes the ankle able to push you forward (transfer force to the ground with pulsion (drive)). Greatest force pushing you forward would be happeing in the terminal stance with the muscle helping be the semitendinosus or gluteus maximus.

If you are everting too much on foot

Green line - Wear too much on the anterior support (ball of the foot) of the foot. They are not able to invert their ankle when they need to generate that active force. This compromises the ability to produce soft tissue injury.

Excessive eversion

Internal rotation of the tibia is associated with eversion of the ankle puts valgus stress on the knee. Cause of soft tissue injury as will as soft tissue of the hip, because the torque of the femur that is generated. Eversion is like porridge, you don't want too much or very little; you want it just right. (Too much tibial rotation, too much on the bottom of the foot --> injury) (Not enough, not enough force --> injury)

Center of gravity of the gait cycle

Midstance -Center of gravity is behind the foot that is on the ground until the beginning of terminal stance. Transition from midstance to terminal stance. -It passes over the point of contact on the ground at 30%. Terminal stance -Center of gravity continues to move forward until the opposite foot touches the ground.

Cardiac output

Q= SV x HR Stroke Volume x Heart Rate When you are increasing heart volume, stroke volume plateaus at 40% of max VO2... any increase of cardiac output comes from an increase of heart rate.

During which period of time is only one leg on the ground? Trait mark of walking gait.

Single support time -"Single-limb support" -10% to 50% -Midstance till the end of terminal stance When both feet are the ground -Double support time -Two separate periods: -Loading response -Heal contact until opposite toe is off the ground -Preswing -the opposite foot contacts the ground until the right leg leaves the ground.

stance phase(periods) vs swing phase

Stance phase (4 periods) -Loading response -Mid stance -Terminal stance -Preswing and Swing phase (It's own thing)

Center of Pressure: foot

The point on the surface of your foot which the most of the force is centered. It will tract as you invert and evert your foot. You have the highest wear pattern on the heal of your foot. Then moves to the middle of your shoe as you evert. Then you come out through the second and third toes.

As individuals speed up (increase their walking speed)

Their double support time decreases. The faster you walk, the less time both feet spend on the ground. Eventually it goes away with running, because both feet are off the ground.

How many phases are there in the gait cycle?

Two phases: Stance phase -0% to 60% -Where the foot contacts the ground until where the foot leaves the ground. Swing phase -60% to 100% -When the foot comes off the ground until the heel contacts the ground again.

Shoes act like a washer for the leg and ground

We have the spring in our leg that has it's own squishiness and we also have the ground that has squishiness. We need the optimal squishiness that allows the leg not work too hard to absorb those forces. --> Shoes helps with this Soft surface --Shoe that does not (that is less compressive) compress that much. The ground is helping with squishiness. Harder surface --Shoe a little bit more squishier to reduce that muscle activity, because the ground is not going to give, so we need the shoe to do that.

Magnitude vs. rate

What leads to injury -the rate in which the force is applied to the foot Comparing individual's that run on soft surfaces vs individual's that run on hard surfaces -Trail running -impact injuries are seen less -higher mileage -road running Greatest ground reaction force -Individuals that run on soft surfaces produces more force -The surface squishes, so you need to press against it more to be able to move forward. -the rate that is applied is much greater than the magnitude.

Starting point of the Gait cycle (Walking)

You start with Heel strike -Right leg You transition your center of gravity over the foot -10% -30% You generate a ground reaction force -50% Leg swings through -60% -73% -87% Until it contacts the ground again (At the end of gait cycle) -100%

Subtalar Joint Angle (Frontal Plane)

You want an individual's foot directly beneath their ankle. The faster the individual is moving in eversion, the greater the power muscle is required for the muscle to control that eversion; it may lead to injury. If you ask a muscle to produce a lot of power, that may lead to injury.

Increase in muscle activity in the leg (increase rate of force on the foot)

increase in injury How to prevent this -decrease the muscle activity in the foot -Lower limb is different for everyone -it has it's own bounciness (spring)

inversion vs eversion

inversion: moving the sole of the foot inward at the ankle eversion: moving the sole of the foot outward at the ankle

When people walk on ice

they walk slowly, to have enough time to have both feet on the ground; stability. Slower gaits are more stable, because feet are on the ground; higher percentage.