W7 - Control Strategies Flashcards
What is the purpose of activation patterns?
activation patterns that minimise/maximise a task relevant cost/score function(where we try to minimise an error) - early neural aspect is part that is controllable(what we vary between movements)
Name some conscious/subconscious control strategies:
- minimise effort - O2uptake, psychological
- minimise muscle activations - contracting pairs(increases force faster)/singular muscles
- minimise jerk - rate of change of acceleration, rate of change in force, how smooth is muscle contraction rate
- maximise performance outcome
- maximise likelihood of ‘success’
- FORWARD dynamics assess gait, as coincides with the natural sequence of neuromuscular control
Define a skill:
Skill: “the ability to bring about some end result with maximum certainty and minimum outlay of energy” (Schmidt)
What are the methods of studying a skill?
What are simulation models?
- record performance (experimental biomech)
- simulate performance (theoretical biomech)
- optimise technique for various criteria
- select solution that best matches recorded one
based on Newton’s equations of motion
inputs → model → outputs
- Either inputting forces and seeing the movement
Or inputting movement and seeing what forces are needed
Name some constraints (Newell, 1986):
- organismic
- environmental
- task
- organismic:
– stature
– mass
– segmental inertia properties:
the mass/length of individual body segments - environmental:
– gravity
– ground interaction
– equipment - task:
– velocity
– duration
– balance
Describe the local/global optimum graph:
What are humans better at?
- local optima are small dips
- global optimum is a large dip
Y-axis is something we are trying to minimise(cost)
x-axis is the thing we are varying - Humans are very good at finding local optima(over time)
- Humans are not very good at finding global optimum
Name some studies that are examples of local/global optimum:
- (Gaesser et al., 2022) -> walking techniques in men and women
- (Ren et al., 2007) -> energy consumption based on knee and ankle movement
- (Hoyt & Taylor, 1981) -> horse gait
Why is natural walking speed and style suggested to be the most efficient?
suggests that deviations from a normal gait pattern lead to increased energy cost, which provides further evidence that minimisation of energy consumption is a feature of normal walking
minimising energy cost is a primary motor control objective in normal walking
experimental studies that head motion is smoother than that of the pelvis and the shoulder, to protect the visual and vestibular systems from excessive mechanical disturbance.
inverse dynamics has simpler implementation of the kinematic and kinetic constraints associated with walking.
What conclusions can be made on the Ren et al., 2007 study on walking?
- multiple solutions for the given constraints
- minimum energy closely resembled human gait
- possible other constraints not considered
- when there is a choice of multiple solutions, skilled performance often uses the one that results in the minimum outlay of energy
Explain the finding of the Gait Transitions study: (Hoyt & Taylor, 1981)
Draw the graph
- serve as triggers to change gait
- correspond well with self-selected speed
e.g.: a gradual increase in speed of the treadmill - walk, jog, run
Provide other gait transmission examples:
- Herzog et al., 2015 - cross country skiing
- Davis, 2005 - under somersault on parallel bars
Explain the simulation model created by Hiley and Yeadon 2013 on minimizing joint torques:
- input: athletes prev joint angles
- output: linear & angular momentum = technique
- they tried to manipulate constraints e.g.: minimising cost, joint torques = taught circle technique (novices) is most efficient
- manipulating minimising velocity at release (τ) = elite gymnasts stoop stalder technique, which uses more energy but increases % of success
- increases margin of error, and shows technique choice isnt always to reduce energy cost
What were some issues with the simulation by Hiley and Yeadon, 2013?
What were the 3 optimisations/ cost functions?
- the horizontal velocity and normalized angular momentum at release exceeded the range spanned by the video analysis of the gymnasts
- excessive hip flexion at release from the
bars as this was likely to result in poor body configurations on re-grasping the bars
- minimisation of peak joint torque, 2. production of vertical mass center path, 3. maximisation of angular momentum at release
What was the overall consensus from Hiley and Yeadon, 2012 on female gymnasts upstart?
- repeated simulations 1000 times using same joint angle input but adding noise each time to find elite orientation movement (based on noise in recorded moves)
- used the simulation to maximise %success, which was close to elite gymnast upstart technique
- skilled performers demonstrated lower levels of movement variability in the timings and angles of the shoulder and hip angle time histories
What is the difference between previous research (Yamasaki et al., 2004) and the simulation model (Hiley & Yeadon, 2012)?
Previous research: (Yamasaki et al., 2004)
optimised using:
* minimum jerk
* minimum effort
* minimum torque required to match performances
- Makes movement as efficient as possible, but does not match elite athletes method “goal-directed movement”
Optimisation: maximise success Hiley & Yeadon, 2012
* added lots of noise added to deal with environmental constraints = gymnast technique
