AMC Sem 2 Flashcards
Describe the double pendulum chaos theory
The dbl pendulum has high sensitivity to initial conditions
Low speed start - get stable inphase or anti phase
High speed start - behaves chaotically in an unstable state
What is a fractal
Infinitely complex pattern that is self similar across different scales
Describe dimensions of a fractal
Dimension is not equal to the space it resides in.
Eg Koch snowflake - length measured depends on the size on the measuring stick
Types of self similarity in fractals
Spatial self similarity- shape is repeated at arbitrarily smaller and smaller scales
Temporal self similarity- shape is repeated over time course eg graph has same pattern if over 3 min, over 30 min or over 300 min
Describe physiological fractal example
Lungs
Follow simple rule of go certain distance then divide in 2
Causes surface area to be much bigger than if a traditional geometric structure was followed
More efficient gas exchange
Impact of fatigue and age on self similarity
Likely to go from self similarity to brownian noise
Types of noise + their predictability
White noise - completely unpredictable
1/f noise (pink noise) - some predictability
Brownian noise - more predictable only small variations can occur at any time point
What is standard deviation
Measures how far individual data points are dispersed from the mean of that data set
Can measure magnitude of variation but takes no account of data order
Can’t identify self similar behaviour
What is coefficient of variation
Ratio of the standard deviation to the mean
Higher coefficient of variation = higher variation
Can measure magnitude of variation but takes no account of data order
Can’t identify self similar behaviours
What is entropy
Measure of level of uncertainty or disorder in a given data set
Higher entropy = more uncertainty
It increases as freedom of choice increases
Helps quantify signal regularity
Entropy values
0 = completely predictable
2 = white noise
What is detrended fluctuation analysis
Analyses statistical properties of time series data
Can detect self similarity
Separate data into boxes, make best fit of each box, calculate deviation of each box. Repeat with smaller and smaller boxes
What is plotted on detrended fluctuation analysis graph
Log of root mean square error vs Log of corresponding box size
Detrended fluctuation analysis alpha exponent values
0.5 = white noise
1 = pink noise
1.5 = brownian noise
Heart rate complexity analysis results
Compared young and old
Both had resting HR 65 but ApEn young 1.09 old 0.48
Young - more unpredictable- good as it means it responds better to environment + stressors
Why do we fluctuate
Interactions of lots of different signals
Motor unit recruitment
Motor unit firing
Muscle tendon interactions
Entropy in older and younger females strength based task
Lower SampEn and ApEn in older - decreased complexity
Strength training made no difference
Why get loss of complexity with aging
Denervation renervation process leads to larger, slower motor units
Older people have 20-40% fewer muscle fibres
Define fatigue
Process that can lead to exhaustion
Neuromuscular fatigue = loss in the capacity for delivering force + or velocity of a muscle resulting from muscle activity under load. This is reversible by rest
Define critical power
Maximum rate a muscle can keep up for a long period of time without fatigue
What happens when exercising above critical power threshold
Fatigue occurs, fixed energy reserve is used which determines exercise duration
What happens when exercising at or below critical power
Task is fatigueless
Energy reserves are not used up
What happens during sub maximal exercise (fatigue)
Compensation for fatigue is possible allowing task to be continued but at the expense of maximal force/power generation
