Biomechanics Quiz 3
What is a concentric contraction?
muscle shortens as it contracts
typically creates joint motion
power generation
True or false? Without joints such as the knee and ankle, there would be a much smaller drop in the COM throughout the gait cycle.
false- joints help to minimize the drop of the COM during gait
What are the three sections of the foot?
hindfoot, midfoot, forefoot
What is an isometric muscle contraction?
Muscle remains the same length and stabilizes a joint; burning rubber
What is the difference between EMSt and LMSt?
Knee GRF transitions from posterior to anterior
How many degrees of extension are available at the MTP joints?
55 degrees
In what ways does the ankle joint assist in minimizing COM drop?
heel rise (TSt) on one foot
neutral ankle (TSw/IC) on other foot
What is stride length?
one full gait cycle- 2 steps (2 successive contacts of same foot)
Interpret ankle at MSt w.r.t. functional tasks
PFors contract eccentrically to control the rate of dorsiflexion and tibial progression; causes knee extension to help with stability
Coronal moments at the hip joint when the GRF is lateral
External - abduction
Internal - adduction
What are the subphases of gait (in order)?
IC
LR
EMSt
LMSt
TSt
PSw
ISw
MSw
TSw
What happens to the calcaneus during LR --> MSt?
calcaneus EV to 5 degrees
With each increasingly proximal amputation, there is a loss of?
lever arm and function
Concentric/eccentric actions of glutes
Concentric - hip extension
Eccentric - controls the rate of hip flexion
What GRF principle is fundamental to orthotic and prosthetic intervention?
Affecting the position & size of the GRF can change the moments created at the joints and significantly impact the muscular demands on a person standing or walking
What percentage of the gait cycle is IC?
0-2%
What happens to the calcaneus during TSt?
progressive reduction of eversion from 5 degrees to 2 degrees of EV (relative INV)
What is the percentage breakdown of stance phase?
10% initial double limb support, 40% single limb support, 10% terminal double limb support
Interpret ankle at MSw w.r.t. functional tasks
Ankle DFors contract isometrically to maintain swing limb clearance & clear toe
What can be a complication of long-term knee valgus?
Osteoarthritis in the lateral knee
What is the position of the hip, knee, and ankle during IC?
hip: 20 degrees FL
knee: neutral
ankle: neutral
True or false? The purpose of STJ INV/EV is to affect the lower limb's ability to absorb shock and create stability/rigidity through the MLA.
true
What are the bones of the midfoot?
navicular, cuboid, medial/intermediate/lateral cuneiforms
Interpret knee at MSw w.r.t. functional tasks
Eccentric hams control the rate of knee extension to avoid terminal impact (knee reaching extension too quickly resulting in shorter step length)
How to minimize CoM drop?
Heel rise in terminal stance (preserves height); neutral ankle in terminal swing (less space b/t ground and foot for IC)