walking mechanics.2

What is meant by the phrase “walking is controlled falling?”

Walking is a continuous cycle of losing and regaining balance as the body falls forward and the swing limb catches the COM.

Where is the body’s center of mass (COM) located in standing?

Just anterior to S2.

What are the two normal movements of the COM during gait?

Vertical displacement and side-to-side displacement.

Why does the COM move during gait?

To allow efficient forward progression while minimizing energy expenditure.

How much does the COM move vertically during normal gait?

Approximately 5 cm.

How much does the COM move side-to-side during normal gait?

Approximately 4 cm.

When is the COM at its lowest point?

Midpoint of double limb support (≈5% and 55% of the gait cycle).

When is the COM at its highest point?

Midpoint of single limb support (≈30% and 80% of the gait cycle).

Why is the COM lowest during double limb support?

Both limbs share body weight and the knees are slightly flexed.

Why is the COM highest during single limb support?

The stance limb is fully extended, elevating the pelvis and body.

What happens if vertical COM displacement becomes excessive?

Walking becomes less energy efficient.

When is side-to-side COM displacement greatest?

Midpoint of single limb support.

When is side-to-side COM displacement smallest?

Midpoint of double limb support.

How does a wider step width affect COM displacement?

Increases lateral displacement and energy expenditure but improves stability.

How does a narrower step width affect COM displacement?

Decreases displacement, improving efficiency but reducing stability.

Why is the COM never directly over the base of support during single limb support?

Walking requires controlled imbalance to move forward.

Why is frontal plane hip control essential during gait?

It stabilizes the pelvis and controls lateral COM movement during single limb support.

Which muscles primarily control frontal plane pelvic stability?

Gluteus medius and gluteus minimus.

What gait deviation results from weak hip abductors?

Trendelenburg gait.

What is potential energy?

Energy of position.

When is potential energy highest during gait?

When the COM is highest (mid single limb support).

When is potential energy lowest during gait?

When the COM is lowest (mid double limb support).

What is kinetic energy?

Energy of motion.

When is kinetic energy highest during gait?

When the COM is lowest (mid double limb support).

When is kinetic energy lowest during gait?

When the COM is highest (mid single limb support).

How are kinetic and potential energy related during walking?

As potential energy decreases, it converts into kinetic energy.

Why is the exchange between kinetic and potential energy important?

It minimizes muscular work and conserves energy.

At what age do infants typically begin crawling?

Approximately 6–13 months.

At what age do infants typically pull to stand?

Approximately 8–12 months.

At what age do most children begin independent walking?

Approximately 8–18 months.

Why do young children walk with a wider base of support?

To increase stability.

Why is cadence higher in young children?

Their shorter legs require more steps to travel the same distance.

Why is single limb support time shorter in young children?

Balance is less developed.

How do children’s step length and stride length compare to adults?

Both are shorter.

How does gait speed compare in young children?

Slower than adults.

How do toddlers typically make initial contact?

Flat-foot contact without a heel strike.

By what age does heel strike usually develop?

Around age 2.

How is stance phase knee motion different in toddlers?

Minimal knee flexion.

By what age does adult knee motion during stance usually develop?

Around age 2.

How is lower extremity alignment different during swing in young children?

The entire limb is externally rotated.

By what age does adult limb alignment usually develop?

Around age 4.

How is arm swing different in young children?

Reciprocal arm swing is absent or limited.

When does reciprocal arm swing fully mature?

Through early adolescence.

What two factors influence gait changes in older adults?

Normal aging and pathological conditions.

How is normal elderly gait best described?

A slowed-down version of adult gait.

How does aging affect step length?

It decreases.

How does aging affect stride length?

It decreases.

How does aging affect cadence?

It decreases.

How does aging affect gait speed?

It decreases.

How does aging affect step width?

It increases.

Why do older adults increase step width?

To improve stability by increasing the base of support.

How does arm swing change with aging?

It decreases.

Why does decreased arm swing improve stability?

It decreases trunk rotation and COM movement, making balance easier.

What is the trade-off of decreased arm swing?

Decreased walking efficiency.

How does initial contact change with aging?

Heel strike becomes flatter.

Why do elderly individuals adopt slower gait patterns?

To improve stability and reduce fall risk.

A patient demonstrates excessive trunk lean toward the stance limb. Which muscle is most likely weak?

Gluteus medius.

A patient demonstrates Trendelenburg gait. During which phase is weakness most evident?

Single limb support.

A patient widens their base of support after a vestibular injury. Why?

To improve stability by increasing the BOS.

A patient walks with minimal arm swing after multiple falls. Why is this beneficial?

It reduces trunk rotation and COM displacement, improving balance.

A patient walks with a narrow BOS and excessive lateral sway. What is the likely consequence?

Increased balance challenge and fall risk.

A patient with Parkinson disease has decreased arm swing and shuffling gait. What is the purpose of this gait pattern?

To improve stability, although it reduces efficiency.

During gait analysis you observe contralateral pelvic drop during stance. What impairment is most likely?

Weak stance-side hip abductors.

A patient demonstrates excessive vertical COM movement during gait. What effect does this have?

Increased energy expenditure.

A patient with cerebellar ataxia walks with a wide BOS. Why is this beneficial?

It improves stability despite increasing energy cost.

An 18-month-old walks with a flat-foot initial contact. Is this abnormal?

No, this is age appropriate.

A 3-year-old has persistent flat-foot initial contact. What should you consider?

Delayed development or underlying pathology because heel strike usually develops by age 2.

Why is single limb support the most difficult phase for patients with balance deficits?

The COM is farthest from the BOS and requires maximal hip and balance control.

A patient with hip abductor weakness is asked to walk faster. How will their gait likely change?

Trendelenburg compensation becomes more pronounced.

Why is normal walking considered energy efficient?

Potential and kinetic energy continuously exchange, reducing muscular work.

A patient has excessive lateral trunk lean during stance to compensate for hip abductor weakness. What biomechanical advantage does this provide?

It moves the COM closer to the hip joint, decreasing the hip abductor moment and reducing muscular demand.

A patient begins taking wider, shorter steps after a stroke. What does this suggest?

A compensatory strategy to maximize stability by increasing the BOS and minimizing single limb support time.