STS + SIT Flashcards
Pre extension and extension phase
STS can be broken up into pre-extension and extension phase.
together they form a continuous mvmt
pre extension - the feet move backwards to position the ankle joint posterior to the knee joint - the upper body rotates forward by flexion at the hips and dorsiflexion at the ankles.
Extension - extensor muscles crossing the hips, knees and ankles accelerate the body mass vertically.
Kinematics and kinetics - pre extension phase
in pre extension phase, STS requires an initial generation of horizontal linear momentum of the body mass to move forward over the feet, and the translation of horizontal momentum to vertical momentum at the start of extension phase that propels the body mass vertically into standing
- vertical momentum is brought about by extension of the hips, knees and ankles
- horizontal momentum is brought about by the angular rotation of the hips
muscle activation
tibialis anterior is one of the first muscles to activate(role of foot placement and stabilising heel)
hip, knee and paraspinal extensors reach peak activity together at thigh off to accelerate the body mass vertically once the preparatory muscle activity has ensured the COG is appropriately placed
gastrocs and soleus have additional role of balancing the body mass during the extensor phase and in standing.
Joining STS and starting to walk
in normal subjects forward momentum continues from STS to the first step before the erect standing position was reached
Many stroke patients aren’t able to to merge the two tasks, probably because they have difficulty controlling forward momentum. Instead they stand up first and then taker a step
-TUG test is useful for this as an indication of functional progress as it tests the ability to adapt the basic STS pattern to the task of standing up and walking.
Mechanical effect of different foot placements
- foot placement specifies the distance the body mass has to be moved forward in order to position the COM over the feet.
- therefore - amount of effort required
- standing up with ankles dorsiflexed puts an active stretch on the soleus thus preserving length and extensibility
standing up with one foot in front of the other decreases load through the front foot
stroke patients have tendency to put non-paretic foot back and load it more than paretic
timing and speed of trunk rotation
increasing speed increases momentum
standing up slowly, as many neurological patients do, reduces momentum with the result of that more lower limb muscle force must be produced for a longer period of time
Seat height and STS
higher = less force required lower= more force + momentum required
Sitting down
sitting down is performed by gravity, and movement from the start involves eccentric (lengthening) contractions of the extensor muscles that cross the hips, knees and ankles
forward rotation of the trunk at the hips is a destabilising movement
as the hips near the seat, tibialis anterior contracts strongly to control backwards path of descent, while quads control the knees flexing
repetition of STS exercises is important because
strengthen the extensor muscle groups
improve intersegmental control of the lower limb by training linked mechanics
optimise learning
retraining strategies
keep feet equal to avoid decreased loading on the affected side
seat height lower = more difficult
seat height higher = less difficult
cue to speed up pivoting trunk forward to create more horizontal momentum
“swing your shoulders forward and push down through your feet and stand up”
Progressions for sit to stand
lowering the height of the chair, folding arms, adding weight belt or vest
different environmental contexts to account for
taking longer times to sit up and down
steadying a glass
holding a large object in both hands
stopping and changing direction
